Ear, nose and throat surgery among young Australian children
Marilyn I Rob
A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy
School of Public Health and Community Medicine Faculty of Law University of New South Wales
March 2005
1 TABLE OF CONTENTS
LIST OF FIGURES...... 7
LIST OF TABLES ...... 9
ABSTRACT...... 13
ACKNOWLEDGEMENTS...... 14
CHAPTER 1 RESEARCH BACKGROUND AND AIMS ...... 15
INTRODUCTION ...... 16
RESEARCH BACKGROUND AND SCOPE...... 23
MYRINGOTOMY ...... 23 What is myringotomy? ...... 23 Why is myringotomy performed?...... 23 Prevalence and incidence of acute otitis media and OME ...... 30 Natural history of acute otitis media and OME...... 34 Management of acute otitis media and OME ...... 35 Debate regarding management options ...... 39 Incidence of myringotomy and population prevalence ...... 51 Risk factors for myringotomy ...... 54
TONSILLECTOMY AND ADENOIDECTOMY...... 57 What is tonsillectomy? ...... 57 Why is tonsillectomy performed?...... 57 Prevalence and incidence of tonsillitis and OSAS ...... 58 Natural history of tonsillitis and OSAS...... 59 Management of tonsillitis and tonsillar hypertrophy...... 59 What is adenoidectomy?...... 63 Why is adenoidectomy performed?...... 64 Management of adenoid hypertrophy and infection...... 64 Incidence of tonsillectomy and adenoidectomy and population prevalence ...... 65 Variation in rates of tonsillectomy and adenoidectomy ...... 68 Debate regarding tonsillectomy and adenoidectomy...... 70
NEED FOR CLINICAL PRACTICE GUIDELINES...... 75 What are clinical practice guidelines?...... 78 What is the aim of CPGs? ...... 79 What factors influence the acceptability of CPGs?...... 81 How effective are CPGs? ...... 88 Potential effectiveness of NSW guidelines for paediatric ENT surgery ...... 90 1 CONCLUSION...... 95
CHAPTER 2 EPIDEMIOLOGY OF ENT SURGERY IN NSW: INTRODUCTION & METHODS ...... 99
INTRODUCTION ...... 100
METHODS...... 103 Definition of terms ...... 103 Data source ...... 103 Record selection ...... 105 Statistical analysis ...... 107 Advantages of the ISC data ...... 116 Limitations of the data...... 117
CHAPTER 3 EPIDEMIOLOGY OF ENT SURGERY IN NSW: RESULTS & DISCUSSION ...... 118
RESULTS...... 119 The contribution of ENT surgery to hospital utilisation...... 119 Type of hospital and insurance status...... 120 Incidence of ENT procedures, 1981-1998/99 ...... 120 International comparison ...... 121 Lifetime risk of ENT surgery ...... 126 Trends in surgery rates ...... 128 Trends in age- and gender-specific procedure rates ...... 130 Changes in age profiles, 1988/89-1998/99...... 139 Changes in prevalence of surgery among children aged 0-4 years ...... 141 Procedure combinations over time ...... 143 Geographical variation ...... 145 Management of acute otitis media by general practitioners, 1990/91 and 1998/99 ...... 147
DISCUSSION...... 149 Burden of paediatric ENT surgery on the health system...... 149 Epidemiology of ENT surgery ...... 149 Trends in ENT surgery ...... 149 International comparison ...... 150 Predisposing factors for surgery...... 151 More surgery among young males ...... 152 Increased surgery for the very young ...... 152 Possible explanations for increasing rates among young children...... 153
CONCLUSION ...... 157
2 CHAPTER 4 EFFECT OF GUIDELINES ON RATES OF ENT SURGERY...... 159
INTRODUCTION ...... 160
METHODS...... 161 Study design ...... 161 Data source ...... 161 Statistical analysis ...... 161
RESULTS...... 164 Effect of guidelines on rates of surgery...... 164 Recorded diagnosis compared with guideline recommendations...... 167
DISCUSSION...... 171
CHAPTER 5 UTILISATION OF HEALTH SERVICES BY A COHORT OF NSW CHILDREN: INTRODUCTION & METHODS...... 175
INTRODUCTION ...... 176
METHODS...... 180 Data source ...... 180 Selection of subjects ...... 181 Cohort description ...... 183 Confidentiality...... 185 Record contents ...... 185 Data analysis...... 188 Advantages of the data ...... 193 Limitations of the data...... 194
CHAPTER 6 UTILISATION OF HEALTH SERVICES BY A COHORT OF NSW CHILDREN: RESULTS & DISCUSSION...... 197
RESULTS...... 198
TOTAL CLAIMS FOR HEALTH SERVICES...... 198 Total MBS claims...... 198 Total claims by age of child ...... 198 Month of Claim ...... 199 Number and type of claims made by the cohort from birth to 8 years of age ...... 203 Number and type of claims by gender of child ...... 206 Claims for surgical operations...... 207
INDIVIDUAL PATTERNS OF HEALTH SERVICE UTILISATION...... 210 Total claims per child ...... 210 General practitioner consultations...... 212 3 Specialist consultations ...... 213 Diagnostic procedures, investigations and imaging ...... 214 Pathology services ...... 216 Optometrical services ...... 217 Surgical operations ...... 217 Differences in number of claims by gender of child ...... 218 Number of claims by area of residence ...... 219
DISCUSSION...... 224
CHAPTER 7 CHARACTERISTICS OF COHORT CHILDREN WHO CLAIMED FOR ENT SURGERY ...... 227
INTRODUCTION ...... 228
METHODS...... 229 Study design ...... 229 Data source and details...... 229 Statistical analysis ...... 231 Limitations of the data...... 232
RESULTS...... 236 How many claims for ENT surgery were made and on behalf of how many children? ...... 236 Age at which ENT surgery was performed ...... 236 Type of ENT surgery...... 237 Number of claims for myringotomy...... 238 Gender of children who had ENT surgery...... 239 Type and combination of surgery by gender of child...... 239 Area of residence...... 240 Relationship between ISC and HIC data ...... 242
DISCUSSION...... 247
CHAPTER 8 COMPARISON BETWEEN CHILDREN WHO HAD ENT SURGERY AND THOSE WHO DID NOT ...... 251
INTRODUCTION ...... 252
METHODS...... 253 Study design ...... 253 Data source and details...... 253 Statistical analysis ...... 254 Limitations of the data...... 256
RESULTS...... 257 Bivariate analysis...... 257 4 Multivariate analysis ...... 261
DISCUSSION...... 266
CHAPTER 9 GUIDELINE COMPLIANCE AMONG COHORT CHILDREN WHO HAD ENT SURGERY: INTRODUCTION & METHODS...... 269
INTRODUCTION ...... 270
METHODS...... 273 Study design ...... 273 Criteria for identification of compliance ...... 273
CHAPTER 10 GUIDELINE COMPLIANCE AMONG CHILDREN WHO HAD ENT SURGERY: RESULTS & DISCUSSION ...... 278
RESULTS...... 279 Compliance with specific myringotomy guideline recommendations ...... 279 Evidence of guideline-sanctioned tonsillectomy indications ...... 285
DISCUSSION...... 286
CHAPTER 11 EFFECT OF ENT SURGERY ON HEALTH SERVICE UTILISATION: INTRODUCTION & METHODS...... 290
INTRODUCTION ...... 291
METHODS...... 292 Study design ...... 292 Data source ...... 292 Statistical analysis ...... 292
CHAPTER 12 EFFECT OF ENT SURGERY ON HEALTH SERVICE UTILISATION: RESULTS & DISCUSSION ...... 296
RESULTS...... 297 Bivariate analyses...... 297 Multivariate analyses...... 300
DISCUSSION...... 318
CHAPTER 13 TOTAL COST OF ENT SURGERY...... 320
INTRODUCTION ...... 321
METHODS...... 323 5 Definition of terms ...... 323 Study design ...... 323 Data source and details...... 323 Limitations...... 328
RESULTS...... 329 Perisurgery costs for children (N=232) who had myringotomy...... 329 Perisurgery costs for children (N=149) who had tonsillectomy...... 330 Perisurgery costs for children who had ENT surgery...... 331 Difference between surgery and non-surgery group in total MBS claims over 8 years...... 333 Estimated annual excess MBS cost for all NSW children who have ENT surgery ...... 337
DISCUSSION...... 338
CHAPTER 14 CONCLUSIONS...... 340
INTRODUCTION ...... 341 What is the level of NSW ENT surgery rates and trends, and how internationally comparable are these?...... 346 Did guideline dissemination in NSW affect the rate of surgery and were guideline recommendations followed?...... 351 Prior to surgery, did children who had surgery use more health services than those who did not have surgery?...... 354 If the prior use of services by children who had ENT surgery was higher, did surgery result in decreased use of services? ...... 360 What is the impact of ENT surgery on the health system? ...... 368
FINAL CONCLUSIONS ...... 370
REFERENCES...... 374
APPENDICES ...... 401
6 LIST OF FIGURES
Figure 1.1 Nasopharynx and Eustachian tube...... 25 (Sources: Bluestone and Klein, and Newnes Pocket Medical Dictionary 4 22)...... 25 Figure 1.2 Extrinsic obstruction of Eustachian tube by adenoids...... 29 (Source: Bluestone and Klein4) ...... 29 Figure 3.1 Comparison between NSW, Scottish and Canadian tonsillectomy rates/1,000 children aged 0-14 years, 1981 - 1991...... 123 Figure 3.2 Myringotomy rates: NSW compared with East Anglia/Oxford...... 125 Figure 3.3 Rate of ENT surgery per 100,000 NSW children aged 0-14 years, . 128 Figure 3.4 Estimated and observed age-specific tonsillectomy rates/100,000 children, 1981-1998/99...... 132 Figure 3.5 Estimated and observed age-specific adenoidectomy rates/100,000 children, 1981-1998/99...... 135 Figure 3.6 Estimated and observed age-specific myringotomy rates/100,000 children, 1981-1998/99...... 138 Figure 3.7 Age profile for tonsillectomy, 1988/89 and 1998/99 ...... 139 Figure 3.8 Age profile for adenoidectomy, 1988/89 and 1998/99...... 140 Figure 3.9 Age profile for myringotomy, 1988/89 and 1998/99 ...... 140 Figure 3.10 ENT surgery combinations, 1981-1998/99 ...... 145 Figure 4.1 Actual and estimated rates of tonsillectomy, adenoidectomy and myringotomy per 100,000 children, with trends pre- and post-guidelines...... 167 Figure 6.1 Total MBS claims over 8 years by age at time of claim...... 198 Figure 6.2 Number of MBS claims per month, January 1990 - December 1997, in a cohort of children born in NSW in January 1990...... 200 Figure 6.3 Observed claims per month compared with regression estimates by age 201 Figure 6.4 Observed and estimated (non-transformed) claims per month...... 203 Figure 6.5 Total claims per child, 1990-1997...... 210 Figure 6.6 Transformed claims per child, 1990-1997...... 211 Figure 6.7 Number of GP consultations per child, 1990-1997 ...... 212 Figure 6.8 Number of specialist consultations per child, 1990-1997 ...... 213 Figure 6.9 Number of diagnostic procedures, investigations and imaging per child, 1990-1997...... 214 Figure 6.10 Number of pathology services per child, 1990-1997 ...... 216 Figure 6.11 Number of surgical operations per child, 1990-1997...... 217 Figure 6.12 Total claims per child by gender, 1990-1997...... 218 Figure 6.13 Number of GP consultations per child by gender, 1990-1997 ...... 219 Figure 8.1 Observed and estimated mean MBS claims by month of age and surgery group: children who had ENT surgery, prior to surgery, compared with those who did not have surgery ...... 263 Figure 12.1 Estimated number of claims per month for children who had tonsillectomy at under four years of age, at four years of age and at older than four years...... 303
7 Figure 12.2 Estimated number of claims per month for children who had myringotomy at under three years of age, at three years of age and at four years or older...... 309 Figure 12.3 Level of claims by month of age: children who had myringotomy or tonsillectomy compared with those who did not have ENT surgery...... 315 Figure 13.1 Observed and estimated MBS claims per month by age: children who had ENT surgery compared with those who did not ...... 335
8 LIST OF TABLES
Table 1.1 Questions addressed in the current program of research and relevant results chapters ...... 97 Table 2.1 Broad geographical group and Area Health Service by population and presence of highest-ranking hospital ...... 112 Table 3.1 Percentage of total hospital separations of NSW children due to ENT surgery by age of child, 1998/99 ...... 119 Table 3.2 Number of NSW children aged 0-14 years who had an ENT procedure and rates/100,000 in each year, 1981 - 1998/99...... 121 Table 3.3 Tonsillectomy rates/1,000 children in NSW and internationally, 1961– 1990 122 Table 3.4 Myringotomy rates/1,000 children in NSW and internationally, 1975– 1991 124 Table 3.5 Risk of NSW children having ENT surgery by age 15 years in...... 126 Table 3.6 Cumulative risk of NSW children having ENT surgery by single year of age, from 1989/90 and 1998/99 lifetables...... 127 Table 3.7 Estimated trends in rates of ENT procedures, 1981 - 1998/99...... 129 Table 3.8 Observed age- and gender-specific tonsillectomy rates per 100,000 NSW children, 1981 – 1998/99...... 130 Table 3.9 Estimated age- and gender-specific trends in rate of tonsillectomy: 1981 - 1998/99...... 131 Table 3.10 Observed age- and gender-specific adenoidectomy rates per 100,000 NSW children, 1981 – 1998/99 ...... 133 Table 3.11 Estimated age- and gender-specific trends in rate of adenoidectomy: 1981 to 1998/99...... 134 Table 3.12 Observed age- and gender-specific myringotomy rates per 100,000 NSW children, 1981–1998/99 ...... 136 Table 3.13 Estimated age- and gender-specific trends in rate of myringotomy between 1981 and 1998/99...... 137 Table 3.14 Rate of tonsillectomy per 100,000 children for seven successive cohorts born 1988/89 to 1994/95 by age at time of surgery...... 141 Table 3.15 Rate of myringotomy per 100,000 children for seven successive cohorts born 1988/89 to 1994/95 by age at time of surgery...... 142 Table 3.16 Age-specific prevalence of surgery per 100,000 children: cohort born during 1988/89 compared with cohort born during 1994/95...... 143 Table 3.17 Percentage of ENT procedures performed singly or in combination, 1981 - 1998/99...... 144 Table 3.18 Indirectly Standardised Ratios by Area/District Health Service for tonsillectomy, adenoidectomy and myringotomy, 1992/93 ...... 146 Table 3.19 Inter-area variability indices for tonsillectomy, adenoidectomy and myringotomy, 1988/89 – 1992/93 ...... 147 Table 4.1 Results of Poisson regressions by type of ENT procedure...... 164 Table 4.2 Estimated trends in rates of ENT surgery pre- and post- tonsillectomy and myringotomy guidelines ...... 165
9 Table 4.3 Selected diagnoses recorded for children who had myringotomy, adenoidectomy or myringotomy and adenoidectomy: 1988/89 compared with 1998/99 ...... 168 Table 4.4 Selected diagnoses recorded for children who had tonsillectomy or tonsillectomy with adenoidectomy: 1988/89 compared with 1998/99...... 169 Table 4.5 Selected diagnoses recorded for children who had tonsillectomy with myringotomy, or tonsillectomy with myringotomy and adenoidectomy: 1988/89 compared with 1998/99 ...... 170 Table 6.1 Average number of claims per child by age...... 199 Table 6.2 Total (log) claims by age of child and season of year...... 200 Table 6.3 Total claims by age of child and season of year...... 202 Table 6.4 Total claims by MBS Category, 1990-1997...... 204 Table 6.5 Total claims by MBS Group, 1990-1997 ...... 205 Table 6.6 Total claims by gender of child ...... 207 Table 6.7 Type of surgical operation, 1990-1997 ...... 208 Table 6.8 Number of surgical operations by gender of child, 1990-1997...... 208 Table 6.9 Number of surgical operations by age of child...... 209 Table 6.10 Proportion of children in each Area of residence who had more claims than the NSW median*...... 220 Table 6.11 Proportion of children in each Area of residence who had more GP claims than the NSW median* ...... 221 Table 6.12 Proportion of children in each Area of residence who had more specialist claims than the NSW median* ...... 222 Table 6.13 Proportion of children in each Areas of residence who had more claims for surgical operations than the NSW median* ...... 223 Table 7.1 Number and rate per thousand cohort children who had ENT surgery by surgery type and age at time of surgery...... 237 Table 7.2 Number of children who had ENT surgery during their first eight years by type and combination of surgery ...... 238 Table 7.3 Number of claims for myringotomy per child...... 239 Table 7.4 Type and combination of ENT surgery by gender of child...... 240 Table 7.5 Percentage of children who had ENT surgery during the eight years by area of residence at time of final claim...... 241 Table 7.6 Percentage of children who had ENT surgery during the eight years by broad residential group ...... 242 Table 7.7 Actual experience of tonsillectomy: HIC cohort compared with NSW ISC cohort aged <1 year in 1989/90...... 245 Table 7.8 Actual experience of myringotomy: HIC cohort (born January 1990) compared with NSW ISC cohort < 1 year in 1989/90...... 246 Table 8.1 Average number of MBS claims made over eight years by children who did or did not have ENT surgery ...... 257 Table 8.2 Claims for GP consultations per child during the eight years by ENT surgery status...... 258 Table 8.3 Claims for specialist consultations per child during the eight years by ENT surgery status ...... 258 Table 8.4 Total optical claims per child over eight years by ENT surgery status 259 10 Table 8.5 Total diagnostic tests per child over eight years by ENT surgery status 259 Table 8.6 Total X-rays per child over eight years by ENT surgery status ...... 260 Table 8.7 Total pathology claims per child over eight years by ENT surgery status 260 Table 8.8 Estimated MBS claims by month of age: non-surgery group compared with surgery group prior to surgery...... 261 Table 8.9 Annual estimated total claims for surgery and non-surgery groups..... 264 Table 8.10 Estimated cumulative claims by specified ages by surgery status ... 265 Table 10.1 Number of GP visits per child in 6 months prior to myringotomy .. 279 Table 10.2 Number of specialist consultations per child in 6 months prior to myringotomy ...... 280 Table 10.3 Total audiology claims made by children in six months prior to myringotomy by MBS item number...... 281 Table 10.4 Number of audiology assessments per child during six months prior to myringotomy ...... 282 Table 10.5 Audiology assessment during six months prior to myringotomy by age 283 Table 10.6 Prior audiology assessment by area of residence ...... 284 Table 10.7 Prior audiology assessment by broad area of residence ...... 285 Table 12.1 Mean claims per child: perisurgery period, year before surgery and year after surgery...... 297 Table 12.2 Mean claims per child for GP consultations: perisurgery period, year before surgery and year following surgery...... 298 Table 12.3 Mean claims (excluding GP consultations) per child: perisurgery period, year before surgery and year following surgery...... 299 Table 12.4 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy when aged less than four years ...... 300 Table 12.5 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy at four years of age...... 301 Table 12.6 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy when aged five years or older...... 302 Table 12.7 Estimated claims per month by age at tonsillectomy ...... 304 Table 12.8 Estimated extra claims during perisurgery period by age at tonsillectomy ...... 305 Table 12.9 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy when aged under three years ...... 306 Table 12.10 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy at three years of age...... 307
11 Table 12.11 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy at four years of age or older...... 308 Table 12.12 Estimated claims per month by age at first myringotomy...... 311 Table 12.13 Total estimated six-monthly claims in first three years by age at time of first myringotomy...... 311 Table 12.14 Estimated extra claims during perisurgery period by age at first myringotomy ...... 312 Table 12.15 Trend in claims over 8 years: children who did not have ENT surgery compared with those who had tonsillectomy or myringotomy at two ages: when very young for the type of surgery or not...... 314 Table 12.16 Age-specific claims: no surgery compared with surgery at younger and older than modal age ...... 316 Table 12.17 Estimated cumulative claims by specified ages: surgery and non- surgery groups ...... 317 Table 13.1 Myringotomy perisurgery benefits paid by Medicare ...... 329 Table 13.2 Tonsillectomy perisurgery benefits paid by Medicare ...... 330 Table 13.3 Comparison between tonsillectomy and myringotomy perisurgery costs per child by type of MBS item ...... 331 Table 13.4 Type and combination of ENT surgery with estimated costs...... 332 Table 13.5 Number of MBS claims as a factor of age and ENT surgery status, taking into account effect of perisurgery period...... 333 Table 14.1 Summary of findings from the program of research ...... 342
12 ABSTRACT
Tonsillectomy, adenoidectomy and myringotomy are the most common surgical procedures undergone by children. Medical opinion regarding the appropriateness of these procedures remains contentious, and considerable resources have been expended in the formulation and distribution of relevant practice guidelines. The impact of this surgery on the child, community and private and public health resources is considerable, yet there has been little examination of surgery rates and trends, or of the characteristics of children who undergo surgery. This thesis addressed five major questions regarding this surgery in New South
Wales, Australia. The first three related to population rates: the level of surgery among NSW children, comparability with international rates, trends over time and the effect of guidelines.
Comprehensive hospital data between 1981 and 1999 were analysed. Major findings were a higher myringotomy rate in NSW than reported internationally, the short-term effect of guidelines, and a major shift towards children having surgery at a younger age. The remaining questions asked whether children who had surgery differed from other children in their use of health services prior to surgery, and if so, whether their utilisation reverted to the norm following surgery. Matched records of a population cohort of 6239 NSW children, born during January 1990, were extracted from Health Insurance Commission data, and their claims for medical services followed retrospectively from birth to 8 years. Children who had privately funded surgery were found to use more medical services than other children, and, most unexpectedly, this did not change following surgery. The results suggest potential non- clinical factors influencing this excess utilisation. This is the first population study to examine health service utilisation by these children and it has identified an important new risk factor for surgery.
13 ACKNOWLEDGEMENTS
I am deeply grateful to my supervisor, Associate Professor Johanna Westbrook, for her invaluable guidance, and for her inspiration, intelligence and friendship. I wish also to thank my associate supervisor, Professor Richard Taylor, for his quick understanding and insightful advice. His suggestions were always apt and valuable. Also, I wish to thank Dr. Louise
Rushworth for her interest and her professional advice in the early stages of my thesis.
I acknowledge the assistance given to me by the NSW Health Department and by the Health
Insurance Commission in their provision of the data, without which this thesis would not have been possible. Thanks too are due to Paul Corben, who assisted me in obtaining the cohort data from the Health Insurance Commission. I am very grateful to have been allowed this marvellous opportunity to explore a fascinating field. I thank Professor Helena Britt for performing on my behalf a special analysis of the General Practitioner survey data. Also, thanks to Margaret Williamson for her generous help.
On the home front, I wish to thank my husband for putting up with my complaints about the thesis over a long period and for having to make adjustments to our life together to accommodate its demands. He has always supported me and encouraged me to persist.
I also wish to thank my children and grandchildren for their interest and encouragement. In conclusion, I wish to acknowledge the contribution of dear family members, long gone, who originally instilled in me a sense of worth and faith in my abilities. And finally, yes, Professor
Geoffrey Berry, I was indeed “very rash” in taking this course instead of a peaceful retirement! But I have since discovered that I am only following the instincts of my Scottish intellectual heritage!
14 CHAPTER 1 RESEARCH BACKGROUND AND AIMS
This chapter presents the scope and aims of this program of research. It describes the three most common types of paediatric ear, nose and throat surgery and reasons for their performance. It presents known population rates and trends over time, and debate regarding surgical thresholds. Gaps in current knowledge with regard to rates of ENT surgery among
New South Wales children and the effect of guidelines are identified. A rationale is presented for testing a hypothesis of differential use of health services by children who have such surgery, and the effect of surgery on their subsequent patterns of utilisation.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background study: of health compliance ENT surgery & aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 14 Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Conclusions Research Introduction Introduction Introduction Introduction
background & methods & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 13 Chapter 4 Chapter 7 ENT Economic Effect of cohort impact: guidelines on utilisation: Results & rates Results & discussion discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
15 INTRODUCTION
The most common surgical procedures among children are the three ear, nose and throat
(ENT) procedures, tonsillectomy, adenoidectomy and myringotomy 1. These procedures are the focus of this thesis. Despite the long-established nature of these procedures, medical opinion regarding their appropriateness remains polarised. ENT surgery is a major cause of paediatric hospitalisation, yet in New South Wales (NSW), the most populous State of
Australia, there is no systematic monitoring of procedure incidence. No long-term analysis of trends has occurred, nor has there been any in-depth analysis of factors which might underlie surgery. Although guidelines regarding surgical thresholds for these procedures have been disseminated in NSW, no empirical investigation into their effects on rates has been undertaken. This thesis aims to address all these aspects regarding this important area of child health. It will comprehensively examine the prevalence and incidence of these procedures and trends over a lengthy period of time among children resident in NSW, and determine the effect of guideline dissemination on procedure rates and other aspects of clinical practice .
The thesis will seek to identify new risk factors for surgery by investigating the characteristics of children who have surgery, specifically, their prior use of health services outside the hospital setting. It will also examine the effect of surgery on these children’s subsequent use of health services.
16 ENT surgery is performed in response to common childhood conditions. Children suffer frequent infections of the ear or upper respiratory tract, some of which may require surgical intervention if medical treatment fails to resolve the problem. The value of such intervention is disputed2-8. Although, in the case of myringotomy, there is evidence of the short-term benefits of surgery compared with no treatment9-12, long-term outcomes have rarely been documented.
These ENT procedures are not performed in response to life-threatening conditions. They are procedures carried out at the discretion of the clinician, subject to the approval of the child's custodian and the availability of resources. Hospital waiting lists suggest that demand for such elective surgery exceeds supply in publicly provided and funded facilities. No such constraint exists in the private health sector. The exact proportion of paediatric hospitalisation due to
ENT procedures among NSW children is currently unknown.
Some elective surgery may be unnecessary, that is, its benefits may not exceed its costs and may not be superior to alternative less costly or invasive forms of treatment or to no treatment at all. Performance of unnecessary services, even those ostensibly privately funded, has indirect consequences for the entire health system. In Australia, the public purse funds many elements of "privately-funded" procedures. The private health funds usually pay for the cost of hospitalisation, but the surgeon's and anaesthetist's fee and the many tests surrounding the procedure are funded to a specified extent by the Australian national health scheme,
Medicare. Private health insurance itself is also heavily subsidized by the Commonwealth
Government. The impact of these surgical procedures on the child, on the community and on private and public health system resources is considerable. Hence there is concern that
17 unnecessary surgery, that is, surgery the costs of which outweigh the benefits, be avoided and that the surgical decision be evidence-based.
Considerable expert resources have been expended in the formulation and distribution of practice guidelines for the ENT procedures12-17. These guidelines aim to ensure that surgery is not undertaken where evidence exists that a less invasive form of treatment would be equally or more beneficial; however, the evidence base for guidelines is often quite sparse. It is not known how closely their recommendations are followed, as few such assessments have been attempted.
Most information regarding ENT surgery focuses on the inhospital stay period. Geographical and secular variation in the rate of paediatric ENT surgery has been documented over many years in the United Kingdom and Canada7 18 19. Causes of variation have been attributed to many factors, some of which are supply factors, such as the availability of surgeons and hospital facilities, while others are demand factors, which attribute variation to the type of population, such as their age and gender composition (which is usually adjusted for in variation estimates), their rate of morbidity and patient expectation among the population.
However, variation is most often considered to reflect a lack of consensus among clinicians.
Doctors differ regarding diagnosis, indications for surgical intervention and the value of therapy18. Over time, clinical opinion can change with the emergence of new evidence.
Hence the opinion of primary care physicians is considered the dominant modifiable determinant of variation19.
18 Despite ENT surgery being such an important area of child health, there is a dearth of epidemiological and health services research in this area19. Very little is known regarding the pre- or post-surgery period, nor regarding the utilisation of health services outside the hospital setting. Causes of variation, secular trends, and factors underlying the performance of ENT surgery remain poorly understood. There is little evidence regarding the effect of such surgery on the health and quality of life of children and their carers.
There were four major aims of this program of research. The first aim was to provide a descriptive epidemiology of ENT surgery among NSW children over a prolonged period,
1981 to 1998/99, in order to determine base rates and trends for comparison with international and best practice norms.
This first major aim included the determination of
• age- and gender-specific rates, currently unknown, and the establishment of an age
profile for NSW children for each type of ENT procedure
• secular trends in surgery rates over a long study period, 1981-1998/99, both for the
total NSW paediatric population and for their age- and gender-specific subgroups
• changes in diagnoses over time, as possible evidence of the emergence of new
indications for surgery
• the amount of geographical variation in ENT rates, currently unknown when limited to
the NSW paediatric population
The second major aim of this program of research was to determine the effect of surgical guidelines on ENT surgery. This aim included the determination of:
19 • The influence of guidelines on subsequent procedure rates.
• The proportion of children who underwent combinations of the three ENT procedures,
as compared with guideline recommendations.
• Possible changes over time in procedure combinations.
• Diagnoses for each procedure in comparison with guideline recommendations
• Compliance with guideline recommendations regarding appropriate treatment pre-
surgery
The third major aim of this study was to determine whether there was any factor supportive of the surgical decision which might have been discernible in the health characteristics of children who had ENT surgery. Factors extrinsic to the child – supply of surgeons, physician attitude - are usually held to underlie the performance of surgery. Hence attempts to curb
“unnecessary” surgery typically focus on such measures as providing guidelines to physicians. Rarely are population health characteristics given much credence in explaining the performance of surgery. However, since socioeconomic measures are commonly used as a proxy for morbidity, it is not surprising that population morbidity is usually found to have little influence. In contrast, the current study focussed on the characteristics of individual children to represent possible population determinants of surgery.
Specifically, this third aim of the thesis was to investigate whether children who had ENT surgery possessed distinguishing characteristics that helped explain their surgery. An example of such a characteristic would be a chronic health problem. Such a problem would be reflected in the frequent use of health services. However, it is recognised that the use of health services does not necessarily indicate a health problem. Such use is at the discretion of
20 the user, and, in the case of children, is one step removed, at the discretion of their parents. As well as the presence and severity of specific symptoms, demographic factors, such as patient age, parental education and number of children, and parental interpretation of the disease process 20, may be responsible for the decision to seek medical advice. Nevertheless, in general, health problems do account for most use of health services. Other motivations are atypical. Hence, the pre-surgery utilisation of health services by children who have ENT surgery might help account for the surgical decision, and this part of the research aimed at examining the question whether the utilisation patterns of the children who had surgery differed from the patterns of children who did not. No such examination of the paediatric utilisation of health services outside the hospital setting has been undertaken in NSW.
Specifically, the third major aim of this program of research was to compare the amount and type of health services used by children who had ENT surgery with that of children who did not. This aim included the determination of:
• Paediatric population norms for the use of health services outside the hospital setting
between birth and 8 years of age
• The pattern of use of health services outside the hospital setting by the population
subgroup of children who had ENT surgery prior to their surgery
• Comparative patterns of utilisation according to ENT surgery status
• Among children who had ENT surgery, comparative utilisation patterns according to
age at time of surgery
The fourth major aim of this thesis was to examine whether ENT surgery affected subsequent use of medical services. If surgery is undertaken to alleviate illness, it should resolve the
21 condition. Resolution of illness should result in reduced use of medical services. Hence this part of the research investigated whether, among children who had ENT surgery, the performance of such surgery affected their subsequent pattern of use of health services.
A further aim was to estimate the economic impact of ENT surgery on the Australian
Medicare system.
22 RESEARCH BACKGROUND AND SCOPE
Three paediatric ENT procedures, myringotomy, tonsillectomy and adenoidectomy, are the focus of this program of research. In this chapter, each of the three procedures is described and reasons underlying their performance presented. Expert surgical guidelines regarding the threshold for these types of surgery are reviewed and conflicting views regarding indications for and benefits of surgery presented. Trends in the incidence of paediatric ENT surgery and population prevalence are discussed. Issues and current gaps in knowledge regarding ENT surgery in NSW are identified.
MYRINGOTOMY
What is myringotomy?
Myringotomy is the surgical perforation of the eardrum (tympanic membrane), performed in hospital by a specialist surgeon under general anaesthetic. Following perforation and drainage, tympanostomy tubes (ventilation tubes, pressure equalisation tubes or grommets) are usually inserted. Throughout this study, the label 'myringotomy' will denote myringotomy with or without tympanostomy tube insertion. Tubes are inserted to provide a channel for continuous drainage and to provide pressure equilibrium. In most cases these tubes are expelled spontaneously after a few months. If the underlying condition has failed to resolve, they may be re-inserted, requiring a further surgical procedure.
Why is myringotomy performed?
Myringotomy is most often performed to alleviate sequelae of otitis media with effusion.
Otitis media with effusion (OME) is an effusion within the middle ear space, commonly known as glue ear3. In OME, secretions are generated by the middle ear mucosa at such a high rate and viscosity that the Eustachian tube cannot drain them21. In most patients otitis media is 23 due to abnormal functioning of the Eustachian tube, which can cause secondary mucosal disease of the middle ear4. The function of the Eustachian tube is threefold: (i) protection of the middle ear from secretions from the nasopharynx; (ii) drainage and clearance into the nasopharynx of secretions produced within the middle ear; and (iii) ventilation of the middle ear to equilibrate gas pressure in the middle ear with atmospheric pressure. Ventilation of the middle ear is the most important function of the Eustachian tube, since hearing is optimum when middle ear gas pressure is relatively equal to air pressure in the external auditory canal.
Hence if the Eustachian tube fails to drain into the nasopharynx, the continuing presence of fluid in the middle ear can result in hearing impairment12 21. Diagrams of the Eustachian tube and surrounding structures are shown in Figure 1.1.
24 Figure 1.1 Nasopharynx and Eustachian tube
(Sources: Bluestone and Klein, and Newnes Pocket Medical Dictionary 4 22)
OME is the commonest cause of acquired hearing loss in childhood12 13 23. Hearing loss can be assessed at any age after birth3 12. Although the hearing loss due to OME is usually mild to moderate, 15 – 40 dB13 23, if it occurs at a crucial period in the child's development (usually regarded as during the first three years), it can retard language acquisition and cause
25 behavioural and developmental problems23-25. One small study of preschool children with
OME found that while verbal comprehension was not reduced, expressive language was of a lower standard26. However, following its resolution, OME can result in the long term in poorer high frequency hearing27.
OME can be asymptomatic, and is difficult to diagnose with certainty. One method of diagnosis is otoscopy, which is visual examination of the ear canal and eardrum, using an otoscope, an instrument which provides a light source. In pneumatic otoscopy the mobility of the eardrum is additionally assessed by means of insufflation of air. While otoscopy is a valuable tool for the diagnosis of middle ear pathology when there is tympanic membrane
(eardrum) pathology, it cannot detect chronic silent otitis media28. Hence otoscopy is considered unreliable29, although one trial which evaluated pneumatic otoscopy found it to be highly predictive of OME30. The only certain method of assessment is through tympanometry, which is the measurement of the ability of the tympanic membrane to absorb sound waves. If the eardrum is infected (otitis media) or if fluid is present behind the eardrum, the absorption of sound waves is significantly decreased. The absence of a peak on the tympanogram, a graph produced by the tympanometer which records the reflected sound waves, indicates the presence of fluid in the middle ear29 31 32. Unfortunately, such equipment is not readily available to general practitioners33, although it has been argued that accurate diagnosis can still be made through careful visual inspection of the tympanic membrane for loss of reflected light, with fluid level or bubbles visible through the eardrum. The integrity of such diagnosis is held to be possible only if disposable speculums, which hinder illumination, are not used34. In one study of Australian Aboriginal children admitted to hospital, acute otitis media was diagnosed by the research team in 20 of 31 children using pneumatic
26 otoscopy and tympanometry, while hospital staff who examined the same children only recorded such a diagnosis in 7 of the children. Further training in diagnosis, including cleaning of the earc canal, was made35.
A diagnosis of OME is often made through other indications. A history of ear infections or parental suggestion of hearing problems or speech delay can indicate the presence of long- standing OME 21. Other symptoms of OME can be pain or discomfort, which may cause sleep loss, irritability and bad behaviour 36. Loss of balance and clumsiness, vertigo and tinnitus are further possible symptoms, which can indicate the presence of fluid in the middle ear pressing upon the semicircular canals or cochlea. Poorer language and speech discrimination, fewer verbal interactions and more solitary play are other possible outcomes 23. One study investigating the quality of life among a group of 186 children who had OME measured such matters as physical suffering, speech impairment, emotional distress, activity limitations and caregiver distress, as well as hearing loss37. However, in most studies of OME, hearing impairment is used as a proxy measure of disability rather than these broader symptoms of disability12.
Acute otitis media (infection of the middle ear) is the most frequent precursor of OME36. In fact, acute otitis media and OME are considered to represent different stages of the same disease27 38. The three most common pathogens are haemophilus influenzae, streptococcus pneumoniae and moraxella catarrhalis 39-41, although virus infection is also possible.
Symptoms of acute otitis media are otalgia (earache) and fever. Perforation of the tympanic membrane (eardrum) with discharge (pus) may occur during acute otitis media. This may be followed by a watery effusion, which usually resolves within a short period. The perforation
27 usually heals spontaneously. Acute otitis media carries the risk of a serious complication, mastoiditis, where infection spreads to the mastoid bone behind the ear23. Other rare serious complications include meningitis, brain abscess, facial paralysis, labyrinthitis and lateral venous sinus thrombosis33 42. When three or more episodes of acute otitis media occur within a six-month period, the condition is known as recurrent otitis media. Following resolution of the inflammation of acute otitis media, progression to OME, which is characterised by a viscous effusion, can occur.
OME may also develop following an upper respiratory tract infection, not specifically acute otitis media38. In a study aiming to predict persistent OME, van Balen and de Melker found a strong association between upper respiratory tract infection and the presence of OME at follow-up43. Physiological structure can also play a part. In young children the size and shape of the Eustachian tube are thought to lead to dysfunction and to be a major factor in the development of OME4. In these children the Eustachian tube is small and its angle is relatively horizontal compared with that of older children and adults. This can interfere with drainage. Hence it has been suggested that gastroesophageal reflux could be implicated in the development of OME. Evidence has been found of gastric juice in middle ear effusions collected from children undergoing myringotomy44, while another study found less OME among bottle-fed infants fed in an upright than supine position45.
The adenoids are also implicated. Adenoids are relatively large in young children, and such hypertrophy can promote development of OME, as can adenoidal infection46. Enlarged adenoids reduce the post-nasal air space and can interfere with the drainage of the Eustachian tube into the nasopharynx. In the van Balen and de Melker study mentioned above, the
28 presence of adenoids was found to be an alternative predictor of persistent OME where there was no upper respiratory tract infection. Enlarged adenoids can mechanically obstruct the
Eustachian tube, and there is evidence that, in the absence of infection, OME can be induced by obstruction of the Eustachian tube 47.
Figure 1.2 Extrinsic obstruction of Eustachian tube by adenoids (Source: Bluestone and Klein4)
Medical views on the cause of OME have frequently changed over the past 100 years, and few proposed causes have been underpinned by evidence18. Efforts continue to identify causes of OME. As mentioned above, gastric reflux has recently been suggested as one cause44, with supine posture when feeding the possible mechanism by which this may operate48. Other studies have implicated passive smoking in the development of OME49.
OME can have serious long term effects other than impaired hearing. The resulting persistent negative pressure in the middle ear can cause the tympanic membrane to thin and form a retraction pocket. Such mechanical injury and metabolic disturbance can lead to tympanosclerosis - the growth of fibrous tissue and patches of calcification on the tympanic
29 membrane (eardrum)47. Tympanosclerosis is a frequent sequela of OME in children47 50. Yet among 222 non-selected, otherwise healthy children aged 7 years, 39% of all ears had changes of the eardrum. However, there is a correlation between eardrum abnormality and the frequency of otitis media50. The tympanic membrane may also become irreversibly adherent to the middle ear structures with or without cholesteatoma. Cholesteatoma (a mass formed by surface skin shedding from the outer ear pressing inwards through a perforated eardrum into the middle ear) is a serious condition which can involve major surgery.
Prevalence and incidence of acute otitis media and OME
Upper respiratory tract infection (URTI), which can be a precursor of all the above conditions treated by ENT surgery, is the most common reason for doctor consultation among children.
In one study, 72% of Canadian children aged 2-12 years developed an URTI within 6 months of recruitment20. In 2000/01, among Australian children aged 0 to 14 years, URTI was managed at 17.4% of general practitioner consultations, and acute otitis media at 7.7% of consultations51. In the U.S., children aged 0-4 years received 53% of all antibiotic prescriptions to the paediatric population, most of which were for otitis media52. Most children have experienced an episode of acute otitis media by the age of three years4 48 53 – even by the age of one year41 54. Eight out of ten infants experience at least one episode of otitis media by the age of one year41 55. Among Australian children aged 0-14 years who consulted a general practitioner, 10% were diagnosed with acute otitis media33 56. Among
Chinese children aged 3-6 years examined between May and July 2001, 9.8% had middle ear disease, with 5.3% having retracted tympanic membrane and 5.2% OME57. In the United
States, acute otitis media was reported as the most frequent primary diagnosis at visits to US physician offices by children younger than 15 years15 23 53. In a US study where children were
30 followed from birth to two years of age, 26% of medical visits were found to be due to acute otitis media58. Another large U.S. study found that, during the study year, July 1995 to June
1996, children under 10 years of age averaged 2.9 physician visits for the management of otitis media, and one-fourth of those aged under 2 years had 6 or more such visits59.
Further, this health burden is increasing60. In an analysis of cross-sectional national health survey data collected in three periods, the carer-reported prevalence of recurrent otitis media among United States preschool children increased from 19% in 1981 to 26% in 198861, and continued to increase between 1988 and 199462. In these national surveys, recurrent otitis media was defined as the child having experienced three or more episodes of otitis media in the previous twelve months. Joki-Erkkila found that the percentage of children under 10 years diagnosed with acute otitis media in Finland grew from 14% in 1978/79 to 21% in
1994/95, while surgical treatment doubled from 6% to 12% over the period63. This increase could have been due to a finding that these diagnoses were associated with less febrile illness and spontaneous otorrhea, suggesting less severe attacks and a greater propensity to seek medical attention earlier.
The main risk factors for developing acute otitis media are young age, season of year (winter), low socioeconomic status and exposure to large numbers of children23 39 61. Children in day care were found to have more respiratory infections per year than children in home care64 65, more protracted upper respiratory tract infections66, more OME67 68 and more day care children received tympanostomy tubes69. One meta-analytic review of 21 studies estimated the relative risk of day care outside the home on the development of acute otitis media to be
2.45 (95%CI, 1.51-3.98)70. Lesser risk factors are White race61, genetic background, male
31 gender23 39 54 61 71 and formula feeding54, although some hold the role of breast-feeding in protecting against acute otitis media to be of greater importance72. Acute otitis media has been shown to develop following most cases of bronchiolitis73, and 29% of respiratory tract infections are complicated by otitis media66. Allergy is a known risk factor61: asthma is related to chronic rhinosinusitis74 and rhinitis75, and in turn allergic rhinitis is associated with middle ear disease76. In recent years the prevalence of allergic disease in children has increased77, and allergy has become a major public health problem78.
Otitis media with effusion (OME or glue ear) is also very common in children, especially young children in seasons when the prevalence of the common cold is high46 79. Among
Danish children aged three years, 42% were diagnosed with OME at least once during 4 examinations over a six-month period80. The prevalence of OME at any point of time is lower than the incidence due to the episodes being of short duration (3 months)80. Zielhuis et al reviewed 23 studies published between 1968 and 1986 which gave a total of 56 age-specific prevalence rates for OME. According to bimodal polynomial curves fitted to these data, the highest reported prevalence occurred at 2 years of age (approximately 20% of children), with a secondary peak at 5 years (approximately 16% of children)29. However, one British cohort study found the prevalence of OME to be as high as 25% at 8 months of age and 12% at 43 months81. In this study OME was found to be more prevalent among children attending grouped day care (risk ratio 1.52 (95% CI, 1.23-1.88)). Other studies have reported the risk of acute otitis media to be increased by 2.45 (95% CI, 1.51-3.98) by day care70. One large U.S. study found that children aged 37 to 54 months enrolled in child care arrangements with more than 6 children had higher rates of URTI, gastrointestinal tract illness and ear infections than other children82. Asthma is a risk factor for OME83, as are all forms of allergy and exposure to
32 cigarette smoke84. Acute otitis media is a known precursor of OME – one large Finnish study found the risk of OME to be highly increased (odds ratio 11.9, C.I. 5.7-24.9) during the 3 months following an episode71. The same study found attendance at a day nursery to more than double the risk. It is hence of relevance to this study to note that day care in Australia has increased between 1996 and 1999, with formal care increasing from 20% to 23% of children aged less than 12 years (z=104.1, p<0.0001)85.
However, currently it is unknown whether the incidence of acute otitis media, a frequent precursor of OME, has increased among NSW children.
Reviewers estimate that at any point of time approximately 5% of children aged between 2 and 4 years are likely to have a bilateral hearing impairment as a result of OME12. The size of this impairment is mild to moderate, 15 - 40 dB23, and will persist for as long as the middle ear is filled with fluid, usually at least three months. This hearing deficit is the equivalent of putting plugs in the ear of the patient. Another estimate of the prevalence of temporary hearing loss due to OME is 5% of children aged five years38. Among certain populations, including Native Americans and American and Canadian Eskimos86 87, the prevalence is far worse – in a New Zealand longitudinal survey of Maori children, 25% of 194 children assessed were found to have a hearing loss associated with effusion88. Similarly Australian
Aboriginal children are held to experience the highest rates of bacterial respiratory diseases reported in the literature89. More rapid and earlier bacterial colonization of the nasopharynx was found in Aboriginal than non-Aboriginal infants (5% per day compared with 1% per day)
90. Acute otitis media commenced within 3 months of birth in 100% of these infants, and progressed to OME in 60%, after which it did not resolve. By school age 50% of Aboriginal children are estimated to have hearing loss 91. Recognition of the increased risk of otitis media
33 and its sequelae among Aboriginal children prompted the NSW Health Department to produce a guideline on its prevention and control specifically aimed at this subpopulation 92.
However, due to the small size of these at-risk populations, their higher incidences do not affect national population rates.
Natural history of acute otitis media and OME
The characteristic pain of acute otitis media usually resolves within a few days33. The eardrum may rupture, allowing a discharge of pus, which brings relief. The eardrum then usually heals rapidly. Evidence from meta-analysis of 63 articles showed untreated acute otitis media improved in 61% of children within 24 hours, rising to 80% after 2 to 3 days93. Another analysis of 13 trials showed similar evidence of favourable prognosis: during a median period of 6 months only 13% of children randomised to placebo had 3 or more episodes of acute otitis media and 51% had no further episodes94. Such evidence shows that most children with recurrent acute otitis media improve in the following year, probably due to growth of the child’s immune system and improvement in Eustachian tube function. However, the favourable natural history of acute otitis media is not as pronounced among children younger than 2 years of age41.
OME also has a high rate of spontaneous remission21. Most (59% - 66%) effusion following untreated acute otitis media resolves within the following month, and 74% - 90% by 3 months48 93. However, for OME of unknown duration there was only 28% spontaneous resolution by 3 months, and for chronic OME only 26% resolution by 6 months. An episode of acute otitis media in the first year of life has been found to be a determinant for persistent
(lasting longer than 3 months) OME43.
34
Management of acute otitis media and OME
Options for managing acute otitis media include relief of symptoms (pain and crying), antibiotics - the usual method of management in Australia, and myringotomy without insertion of grommets to release the short-term (pus) effusion33.
For OME, management options include long-term (10-30 days) antibiotic therapy, antihistamine therapy or administration of steroids. Other methods of management are autoinflation of the middle ear (Valsalva technique) and watchful waiting for at least 3 months36. However, this must be genuine; records must be kept21. Educational strategies to compensate for any temporary loss of hearing are also employed. The surgical methods of management of OME are myringotomy with tympanostomy tube insertion, adenoidectomy and tonsillectomy.
U.S. otolaryngologists, asked to rate the relative importance of 22 indicators for grommet insertion95, gave the highest ratings to the following five indicators:
• persistence of fluid for 3 or more months per episode
• presence of speech-language delay
• presence of bilateral conductive hearing loss of 20 dB or more
• total number of episodes of otitis media
• failure of effusion to respond to suppressive antibiotic therapy
Another group of U.S. otolaryngologists has given the following as indications for tympanostomy tube insertion96:
35 • chronic middle ear effusion that is relatively asymptomatic and unresponsive to medical
management for at least 3 months if bilateral or 6 months if unilateral
• recurrent AOM, namely, 3 or more episodes during 6 months or four or more during the
previous year, with one attack being recent
• the presence or suspicion of a suppurative complication
• signs or symptoms of Eustachian tube dysfunction including fluctuating hearing loss,
disequilibrium or vertigo, tinnitus or a severe retraction pocket
• when tympanoplasty is performed due to the presence of cholesteatoma
In November 1994, the American Academy of Pediatrics (AAP) issued guidelines for managing OME in young children (aged 1 to 3 years)15. These guidelines recommend:
• that primary care physicians hold an attitude of suspicion towards symptoms such as
discomfort and behaviour changes following an episode of acute otitis media that might
indicate the presence of OME
• that middle ear status be assessed using pneumatic otoscopy
• that suspected OME be confirmed (optional) using tympanometry
• that a child who has had fluid in both middle ears for a total of 3 months should undergo
hearing evaluation
• that observation or antibiotic therapy be undertaken when OME is present for less than 4
months
• that tympanostomy tubes be inserted after a total of 4 to 6 months of bilateral effusion
with a bilateral hearing deficit
The AAP guidelines specifically recommend against: 36 • placement of tympanostomy tubes when symptoms have been present for less than 3
months
• steroid medications
• antihistamine/decongestant therapy
• adenoidectomy unless adenoid pathology is present
• tonsillectomy, alone or with adenoidectomy
These guidelines were later strengthened and extended to children aged 2 months to 12 years97, recommending that the duration of effusion and severity of symptoms be documented at each assessment, that hearing, speech and language be evaluated promptly and that children be managed with watchful waiting for a period of 3 months.
In 1992, the University of York Centre for Reviews and Dissemination published Effective
Health Care guidelines on the treatment of persistent glue ear in children12. These guidelines recommend diagnosis and assessment of OME through:
• history taking
• otoscopy
• audiometry for children aged 4 years and older
• tympanometry
The Effective Health Care guidelines recommend:
• watchful waiting
• a provisional waiting list for surgery be kept so as not to prolong the waiting for those
children who need surgery at the end of the watchful waiting period
• reassessment immediately prior to surgery with a finding of bilateral glue ear 37 • at least 2 audiological tests conducted over 3 to 6 months
• an audiological test immediately prior to surgery
The Effective Health Care guidelines did not review the effectiveness of medical approaches to treatment of the condition, but assume these to have been exhausted before consideration of surgery.
In NSW in early 1992, the NSW Health Department established a Working Party to develop guidelines for middle ear disease based on best evidence and best professional judgement currently available. The Working Party was multi-disciplinary and included representatives from the Australian Society of Otolaryngology, Head and Neck Surgery, Australian College of Paediatrics, Royal Australian College of General Practitioners, the Audiological Society of
Australia and the Community Audiometrist Association. The resulting "Guidelines on the management of paediatric middle ear disease" was published in the Medical Journal of
Australia in October 199313. For acute otitis media, the guidelines recommend treatment with an antimicrobial agent for 7-10 days - amoxicillin, amoxicillin-clavulanate, cefaclor or, for children allergic to penicillin, trimethoprim-sulphamethoxazole. If no resolution occurs, or if resolution is followed by recurrence within a month, treatment with another antimicrobial agent is recommended. If there is no improvement, or there are frequent recurrent episodes of acute otitis media (recurrent otitis media), specialist consultation is recommended. If there is resolution of infection but persistent effusion occurs, this should be treated as OME.
For OME, the guidelines recommend medical management with an appropriate antimicrobial agent such as amoxicillin for 10-28 days, the aim being to render the effusion sterile,
38 facilitating resolution. If an adequate course fails to resolve the effusion, another antimicrobial agent, one active against ß-lactamase producing organisms, such as trimethoprim-sulphamethoxazole, amoxicillin-clavulanate or cefaclor, should be tried. A 'wait and see' approach (watchful waiting) for at least three months should precede surgical intervention.
These 1993 NSW guidelines recommended tympanostomy tube insertion
• when hearing loss resulting from OME has been present for longer than three months, and
if such hearing loss is resulting in learning or behavioural difficulties
• when there are pathological changes in the middle ear due to the effusion, such as
tympanosclerosis (white patches on the tympanic membrane), retraction pocket formation
(localised thinning of the tympanic membrane) or irreversible adherence of the tympanic
membrane to the middle ear structures, and
• when the effusion fails to resolve with medical management
Debate regarding management options
Antibiotics in the treatment of acute otitis media and OME
Evidence with regard to the benefits of antibiotic therapy is ambiguous. It is estimated that treatment of URTI with antibiotics will prevent 1 in 30 cases of acute otitis media developing in children. Hence there is little benefit in routinely treating URTI with antibiotics.
Acute otitis media is said to be the most frequent reason for antibiotics in the U.S.53. A large study of 22,004 New England children with health insurance showed that amoxicillin was prescribed as initial therapy in 56.6% of all episodes of acute otitis media59. In other
39 countries, such as Holland, antibiotics are not routinely prescribed for acute otitis media.
Such treatment which defers antibiotic treatment of selected children for up to 3 days and provides only analgesics and symptomatic relief has not gained wide acceptance in Europe and the United States98. In Australia, clinicians usually use antibiotics to reduce the incidence of serious complications33. In Finland, greater use of antibiotics in management of acute otitis media resulted in a reduction of symptoms, such as pain, which last longer than 24 hours63, similar to the results of another reported trial, where antibiotics reduced short-term symptoms of acute otitis media by one day when compared with no treatment33. In the U.K., a controlled trial of 232 children with acute earache found treatment failure to be 8 times more likely in the group receiving a placebo than those receiving an antibiotic, with the placebo group showing higher incidence of fever on the second day, analgesic consumption, crying and absence from school99. In The Netherlands a double blind trial of 240 children with acute otitis media concluded that amoxicillin conferred only a modest benefit over placebo after 4 days100. However, in that trial the duration of time to cessation of fever was 2 days with amoxicillin versus 3 days with placebo, and to cessation of pain and crying 8 and 9 days respectively. Meta-analysis of 33 articles has shown that resolution occurred spontaneously within 7 to 14 days in 81% of cases, while antimicrobial therapy increased this rate by a modest 13.7%101. Recent evidence cited by Jackson that antibiotic treatment for acute otitis media has limited effectiveness102 have been criticised as having major limitations103.
Paradise cited these limitations as “limited sample size and statistical power, exclusion of children who seemed ill, enrolment of few or no children younger than 2 years, lack of standardized or stringent criteria for diagnosing acute otitis media or for defining improvement or cure, use of an antimicrobial with less than optimal efficacy against common ear pathogens, and use of lower than optimal drug dosage”. These criticisms are echoed by
40 Wald, who further maintains that overuse of antibiotics results not from their use in the treatment of acute otitis media, but from misdiagnosis of the condition and their indiscriminant use in the treatment of viral upper respiratory infections104 105. However, the rate of such inappropriate antibiotic use has been found to be slowly decreasing106.
In the treatment of OME, some meta-analyses have suggested that antibiotics are ineffective21, while, in another meta-analysis of controlled studies, an increased rate of OME resolution (22.8%) when antibiotics were given was shown107. However, there is no additional benefit in continuing antibiotic treatment beyond 14 days108. Paradise maintains that antimicrobials have definite but limited efficacy in resolving OME, because they help eradicate nasopharyngeal infection or inapparent middle ear infection39. One controlled trial of 518 infants and children found that amoxicillin compared with placebo doubled the rate of resolution of effusion after 4 weeks, although effusions in most (70%) children who received amoxicillin remained unresolved109. The authors concluded that the advantage conferred by amoxicillin was of limited magnitude and of short duration.
Concern remains over antibiotic resistance, which is threatening the efficacy of antimicrobial agents in the treatment of both acute otitis media and OME110 111. One Spanish bacteriological study of children with acute otitis media found that, of the middle ear effusions where
Streptococcus pneumoniae or Haemophilus influenzae was isolated (60% of cases, with 24% having sterile effusions), penicillin resistance was found in 39% and 23% respectively112.
Antibiotic resistance is widespread and increasing40 53 113. The development of resistance is linked to antimicrobial use, day care attendance, young age and prior hospitalisation. Because of this resistance, it is suggested that antiviral drugs now available be evaluated and used to
41 combat the viral pathogens, influenza virus and respiratory syncytial virus, most frequently associated with acute otitis media114. Klein reports that one antiviral drug, zanamivir, has been shown to be effective against influenza A and B in adults, and another, ribavirin, against respiratory syncytial virus (but only in infants), and urges further investigation into the role of these drugs in preventing and treating acute otitis media in children. A clinical trial of a pneumococcal conjugate vaccine had limited success, preventing 9% of acute otitis media episodes115. Such a moderate effect was confirmed in a review of 11 randomised controlled trials116. Strategies of decreasing nasopharyngeal colonisation with Streptococcus pneumoniae and Haemophilus influenzae have also been employed. One clinical trial, using an oligosaccharide as an inhibitor of nasal membrane receptors, found that children given xylitol in chewing gum had fewer episodes of acute otitis media than children using sucrose- containing chewing gum117. However, bacterial adherence is a complex issue118. Klein continues to advocate amoxicillin as the drug of choice for acute otitis media, as he estimates that only 6% of all such cases treated with amoxicillin are expected to fail due to resistant bacteria119. The NSW guidelines advocate antibiotic therapy as the first line of defence, and a recent (1999) Center for Disease Control Working Group recommended amoxicillin as the first line antimicrobial agent, with oral amoxicillin-clavulanate, cefuroxime axetil and intramuscular ceftriaxone as alternative agents in the case of clinically defined treatment failure120.
Steroids and antihistamines in the treatment of OME
Steroids are not favoured in the treatment of OME, since their risks are considered to outweigh potential benefit36. The American Academy of Pediatrics guidelines also recommend against the use of steroid medications owing to lack of evidence of their
42 effectiveness and possible adverse effects (agitation, behaviour change and possible disseminated varicella if exposed to this virus in the month before therapy)15. One study that tested the effectiveness of combined steroid-antimicrobial therapy found a 25% resolution rate compared with 2% among children who received no medication121. However the combined nature of the treatment given confounds these results. A further double-blind trial comparing the effect of steroid and amoxicillin treatment with amoxicillin alone concluded that, although children who received steroid were initially better, after 4 months there was no significant difference between the groups108.
Antihistamines and nasal decongestants are considered to have no benefit15 36, yet it has been reported that treatment for allergies improved the hearing of 200 U.K. children with chronic
OME, and that, when another group of 80 children with perennial allergic rhinitis was tested for hearing problems, only 17 were found to have normal hearing122.
Adenoidectomy in the treatment of OME
Enlarged adenoids are thought to contribute to OME by reducing the post-nasal airway space.
Adenoidectomy has been found to be of benefit where enlarged adenoids have reduced the size of the post-nasal airway space to less than the mean of children who did not have
OME123. However, in three studies of adenoidectomy in the treatment of OME, its efficacy was found to result from the removal of the source of infection in the nasopharynx rather than adenoid size124.
The efficacy of adenoidectomy in the treatment of glue ear is largely contested. AAP recommendations state that adenoidectomy is an inappropriate treatment for OME among
43 children under 4 years of age, unless adenoid pathology is present, and that its potential harms for children of all ages include the risks of general anaesthesia and the possibility of excessive postoperative bleeding15. Yet in Finland otitis media was reported to be the indication for adenoidectomy in 79% of children aged under 4 years125. And while one NSW practitioner maintains that adenoidectomy has largely been replaced by myringotomy in the treatment of
OME due to lack of evidence of its benefit33, others prefer adenoidectomy to myringotomy in cases of persistent OME in that it appears to modify its underlying pathophysiology38.
Another NSW otolaryngologist stated his approach to be to perform adenoidectomy after repeated recurrences of OME, usually in combination with myringotomy with tube insertion36. This is the practice recommended in Italian national guidelines, as well as those of the American Academy of Otolaryngology – Head and Neck Surgery126. The Effective
Health Care guidelines for the treatment of glue ear recommend against combining adenoidectomy with myringotomy in that the added benefit is reportedly very small12. Yet in
Canada, an examination of hospital records between 1995 and 1997 revealed that among children who had tympanostomy tubes inserted and were at least two years of age, those who underwent adenoidectomy in addition to insertion of tubes were less likely (relative risk, 0.6,
95% C.I. 0.4 – 0.8) to be readmitted for reinsertion of tubes or for an otitis media-related condition within 3 years, and readmission was even less likely where both adenoidectomy and tonsillectomy had been performed127. Similarly in a prospective study of children having unilateral grommet insertion randomly assigned to also have adenotonsillectomy, adenoidectomy or neither, Maw and Herod found that the children who had adenoidectomy in addition to grommet insertion required fewer reinsertions to maintain adequate hearing in the treated ear11. In the U.K., parents of children who had had myringotomy reported greater satisfaction with the outcome if adenoidectomy had also been performed128. A Pittsburgh
44 randomised clinical trial showed a statistically significant reduction in the rate of episodes of acute otitis media following adenoidectomy or adenotonsillectomy among children with recurrent otitis media or OME when compared with the control group (for adenotonsillectomy, 1.4 vs 2.1 episodes per year, mainly limited to the first postoperative year); however, the size of this reduction was clinically modest6. The authors conclude that this limited and short-term efficacy does not outweigh the risks, morbidity and costs of these procedures for recurrent acute otitis media.
Tonsillectomy in the treatment of OME
Although enlarged tonsils may also play a role in reducing the post-nasal airway space, no evidence supports the value of tonsillectomy in the treatment of OME13 129 unless indications for tonsillectomy are present in their own right36. In the Maw and Herod study cited above, tonsillectomy was found to confer no additional benefit11. In the Pittsburgh clinical trial summarised in the previous section, despite evidence of a greater reduction in episodes of acute otitis media following adenotonsillectomy than adenoidectomy, neither procedure was recommended6. The 1998 American Academy of Otolaryngology – Head and Neck Surgery guidelines also recommend against the use of tonsillectomy for the treatment of otitis media17.
Despite such recommendations, a 1996 U.K. survey found that one-fifth of tonsillectomies were carried out for otitis media, ear infection or hearing problems130.
Watchful waiting in the treatment of OME
Because the natural history of glue ear is spontaneous resolution, at least three months of watchful waiting is advocated21 93, as is re-confirmation of the presence of glue ear prior to surgery12 28 30 32.
45
During grommet insertion, surgical removal of the content of the middle ear provides 'gold standard' confirmation of the presence of OME. Dry taps (where no glue is found) indicates resolution of the OME and a failure to reassess prior to surgery12. In the NSW guidelines on the management of middle ear disease, this practice of watchful waiting was endorsed.
However, it is unknown whether this specific guideline recommendation has been followed among NSW children having myringotomy, namely:
• whether there is evidence of 'watchful waiting', such as at least 3 physician consultations
in the 6 months prior to surgery
Myringotomy in the treatment of OME
Controversy continues regarding the indications, risks and benefits of surgery46. Short-term modest improvement of hearing when grommets are in place and functioning is held to be undisputed. In the Effective Health Care bulletin 12 many studies into the effect of grommet insertion on hearing are summarised. However, while the three principal cited randomised controlled trials 9-11, reported mean improvements in hearing of 8dB (n.s.), 19dB and 5dB
(n.s.) respectively 6 months after the placement of grommets, these declined to 4.8dB (n.s.),
9.5dB and 0.8dB (n.s.) 12 months after surgery, and in only one trial was the improvement statistically significant. Surgery can also relieve behavioural problems associated with hearing loss24 - concerns about delayed language development and altered behaviour are paramount among both professionals and parents118. In the UK, among preschool children with OME present for at least 3 months and a hearing loss of at least 25dB, the behaviour of those randomly assigned to receive grommets improved immediately after grommet
46 placement by contrast with that of the group waiting to receive grommets131. This behavioural improvement was attributed to their improved hearing. Evidence from 4 meta- analyses and 9 randomised controlled trials has shown that grommets and adenoidectomy both offer modest improvements in hearing, with an average improvement of 12 dB at 6 months and 6dB at 12 months after surgery132. A Scottish randomised controlled trial found that surgery had an effect on the hearing and the presence of OME at 6 months post- operatively, but not at 12 months, when it was no different from natural resolution10. In a recent survey, 365 U.S. otolaryngologists considered grommets to be useful, but not a cure-all for otitis media133. Improved quality of life following tube placement has been reported111.
Another reported benefit of grommets is a reduction in physician office visits for the period (a year on average) that tubes remain in place and functioning134.
Fear of the effect of hearing loss on language acquisition is a common reason for surgery.
However, parents often cannot detect mild hearing loss in children135, while OME-associated hearing loss is generally short-term. One study has shown early recurrent OME not to be associated with speech disorder in a sample of 3 year old children136. A smaller study, which administered multiple speech and language tests to 210 children at age 2 years, retested 36 of the children at 3 to 4 years of age, among whom 9 had had hearing loss at age 2, and found all
9 had normal hearing and had experienced no delay in language acquisition58. In a large study of children under 2 years of age with persistent OME, Paradise et al failed to find any differences in speech, language, cognition or psychosocial development at the age of 3 years between 169 children randomly assigned to have tubes inserted promptly and 66 children who waited for nine months before surgery137, nor did delay affect any developmental outcomes at
4 years of age134. This study was criticised on the basis that most children in the study had
47 unilateral rather than bilateral effusions, most of which were discontinuous, which would hence not be expected to cause developmental delays in otherwise healthy children138. In the
Netherlands among 52 children with and 13 without bilateral OME, while verbal comprehension was not reduced in those with OME, expressive language was26.
Nevertheless, the American Academy of Pediatrics maintains there is a lack of rigorous evidence to support the theory that untreated OME results in speech or language delays or deficits15.
Studies have shown that the treatment of OME by myringotomy is not always effective, even where improvement of hearing is the sole criterion. One long-term observation of Polish children who had grommets inserted found improvement of hearing in only 65%3, while other effects of OME persist despite, or perhaps because of, surgery. In the same study the appearance of the tympanic membrane was normal in only 38% of these children, while 10% had retraction pockets, 8% tympanosclerosis, 6% secretory fluid and 4% perforation of the tympanic membrane. In another long term observation study in Poland, only 60% of 50 patients treated with tube insertion had been healed, while negative pressure was found in the ears of the other 40%, and in 5% even repeated tube insertion failed to prevent the development of adhesive otitis or cholesteatoma5. In Turkey, in re-examination of ears treated with tubes, myringosclerosis (tympanosclerosis) was found among 31% of girls and 71% of boys139. For recurrent acute otitis media, children randomised to receive myringotomy as well as amoxicillin had the same rate of recurrence as those who received amoxicillin alone140, while in another clinical trial the effect of myringotomy alone was no different from that of amoxicillin141. Neither study provides support for the routine use of myringotomy for this condition.
48
In some cases tube insertion has led to worse outcomes than the effects of the OME being treated. In one study the researchers found that placement of the tube led to significantly worse hearing in five patients. It had been assumed that, owing to the small diameter of the tube, the opening in the tympanic membrane should not interfere with the conduction of sound. However, the researchers demonstrated that blockage of the tube with cigarette paper or another medium appreciably improved the conductive hearing of these five patients142.
Another rare, but unwanted, sequel of myringotomy is displacement of the grommet in the middle ear, which has been reported in three cases in the U.K.143. With regard to Eustachian tube function, a recent study of 19 Swedish children found that opening and closing pressures in the middle ear increased between the time of tube insertion and 4- and 9-month follow-up periods144. This was attributed to both the disease and the tube treatment. In the U.K. 48% of
1274 children who received grommets experienced at least one complication during a 4-year study period: 32% experienced persistent perforations, 24% tympanosclerosis, 21% repeated otorrhea or tympanic membrane granulations and 11% impacted wax145. The American
Academy of Pediatrics calculated the risk of tympanosclerosis following myringotomy at 51% of children, and postoperative otorrhea at 13%15. A meta-analysis of 134 articles listed sequelae of intubation as tympanosclerosis (32%), focal atrophy (25%), retraction pocket
(3.1%), cholesteatoma (0.7%) and perforation (2.2% and 16.6% with short- or long-term tubes)146. Such unwanted sequelae are a reason Paradise advocates tympanostomy tube insertion as being appropriate only under specific circumstances134. Prospective studies have found that while the incidence of some sequelae such as tympanosclerosis decline over time, the incidence of more serious sequelae increase147. Eight years after initial tube placement in
84 children, the prevalence of ears with perforation of the eardrum was 2%, and of atrophic
49 scarring, retraction or retraction pocket 55%, and one child had developed cholesteatoma148.
Only 22 of 167 ears had no sequelae, and only 2 children had normal ears bilaterally. A meta- analysis of 134 articles examining the incidence of tympanostomy tube sequelae found an incidence of otorrhea in 16% of patients initially and 26% later, recurrent otorrhea in 7.4% and chronic otorrhea in 3.8%, obstruction by tubes 7% (of ears), medial displacement in 0.5%, granulation tissue in 5% and premature extrusion in 3.9%146. Following tube extrusion, tympanosclerosis was found in 32% of patients, focal atrophy (scarring) in 25%, retraction pockets in 3.1%, perforation in 2.2% with short-term tubes and 16.6% with long-term tubes, and cholesteatoma in 0.7%. One large retrospective study (2829 Israeli children) found cholesteatoma directly attributable to ventilation tube placement in 1.1% of ears149. Children younger than 5 years, those who had had repeated insertions and or prolonged intubation were more likely to develop cholesteatoma.
The 1992 Effective Health Care guidelines for the treatment of glue ear expressed doubts that the levels of surgery in the U.K. were necessary12. One very controversial study asserted that indications for surgery were inappropriate in one quarter of children receiving grommets150.
This study used criteria developed from artificial scenarios rated by a group consisting of 3 otolaryngologists and 5 paediatricians. These indications for surgery were then used in a prospective utilisation review process carried out on behalf of U.S. health insurance companies. This led to a flood of commentators refuting Kleinman’s assertion on various grounds96 151-155. One who was a member of the original rating group criticised the basis of the criteria on which appropriateness was judged, as they were not based on expert guidelines96. Although the criteria were developed using the services of a panel of experts,
Bluestone considers the method of their development flawed, with appropriateness being
50 decided solely on scenario scores, without the benefit of discussion. He warns of the danger of denying access to surgery using criteria derived in such a manner. In a medical record review to determine retrospectively the appropriateness of tympanostomy tube placement, Spilseth concluded that 53% of 38 children were referred appropriately156.
The advantages of tubes have been summarised by Gillespie as improving short-term hearing and reducing the average number of infections, which quickly resolve with the use of broad- spectrum topical therapy, such as quinolones, and their disadvantages as increased cost, need for anaesthesia, dry ear precautions and increased long term perforations157.
There remains no consensus regarding the appropriate rate of surgery12.
In NSW we do not know
• whether children whose reason for having myringotomy was hearing loss had a hearing
test prior to surgery, as recommended in the 1993 NSW guidelines
• whether the diagnosis recorded for children having myringotomy reflects guideline
criteria
• what proportion had a hearing test following surgery to assess outcome
Incidence of myringotomy and population prevalence
The procedure of perforating the eardrum to achieve an improvement of hearing has a long history. However, very early attempts produced such bad results that the practice was abandoned. Attempts in the mid-19th century to create a permanent opening using various
51 materials were similarly unsuccessful158. With technological advances in the composition of the tube, grommets were reintroduced as a 'new therapy' in the middle of the 20th century.
Since their introduction, most studies have found rates of myringotomy to increase until the end of the 1980s. In Scotland a sixty-fold increase between 1966 and 1986 was reported159, while in England the rate for children aged less than 10 years increased between 1975 and
1983 to the extent of being described as an 'epidemic' of surgery160. However in 1995 Black reported the 'epidemic' to be waning161, and has since reported that, after reaching a peak by
1986 of 132 per 10,000 children aged under 10 years, myringotomy has declined to 120 per
10,000 by 1992/931, and a decline in Scotland between 1990 and 1994 has also been reported162. Comparative changes in grommet insertion rates over time are reported as:
Country Characteristics of Changed from Changed to children Year Rate Year Rate England1 < 10 years 1986 132/10,000 1992/93 120/10,000 Scotland159 1966 1986 60-fold inc Finland63 < 10 years, with OME 1978 6% 1994 12% NSW163 < 15 years 1986 5.8/1,000 1989/90 7.6/1,000 Netherlands (estimate)164 < 13 years 1990 1.68% 1992, 2.18%, 1994 2.05%
By contrast, in Italy, where a policy of only using grommets for persistent OME has been pursued, there was a reduction in the rate of grommet insertion between 1981 and 1993165.
Similarly, one U.S. study found rates of myringotomy decreased threefold between 1977 and
1987166, but these data did not include day case or military surgical facilities.
Hence rates are difficult to compare due to differences in age of the children studied and period of reporting. The 1992 Effective Health Care guidelines reported the average annual rate in England as 5/1000 children aged 0-14 years12. In 1990 in Scotland the myringotomy rate was 4.7/1000 children aged under 16 years167. Grommet insertion is the most common 52 surgery for children under 15 years in the U.S.53. In the U.S., the prevalence of myringotomy was quoted as 13/1000 children under 18 years168. In a nationally representative longitudinal study where 8285 children were followed from birth to 3 years of age, 6.8% of U.S. children were found to have had grommets inserted by this age53. This agrees with the reported annual incidence between 1997 and 2000 among Canadian children aged 1 year of 54.2/1000169
(Desai). The same study reported the incidence for children aged 0-14 years at 11.1/1000, while another Canadian study reported the rate between 1996 and 1999 for children aged 0-14 years as 8.35/100019.
Geographical variation in rates of myringotomy within the same country is generally found to be considerable. In NSW geographical variation in rates of myringotomy and the other ENT procedures (not limited to the paediatric population) has persisted over a number of years170.
In Canada between 1996 and 1999, where rates between counties were found to vary ten-fold, and in England during the years 1975-1980 this variation was considered attributable to professional uncertainty rather than availability of medical care18 19. Black found high rates of myringotomy to be positively associated with social class160. Disease prevalence among the population is not considered the dominant factor underlying variation168 171.
Currently in NSW we do not know
• the rate of myringotomy among the paediatric population
• long-term trends in rates of myringotomy
• the percentage of myringotomy procedures performed in combination with adenoidectomy
or tonsillectomy
• whether this percentage has changed over time
53
Risk factors for myringotomy
Extreme youth is a risk factor for myringotomy - young children have the highest rates. In the
U.S. 6.8% of children were found to have had grommets inserted by three years of age53. In the Netherlands, the highest rates of surgery were found among children aged 2 years and 6 years164, and in NSW in 1989/90 children aged under 5 years had the highest rates163. In
Canada between 1996 and 1999 rates were found to peak at ages 1 year and 4 years, with respective rates of 20.4/1000 and 16.3/100019.
Boys are more likely than girls to have grommet insertion12 19 53 163 167 168. However, no attempts to explain this gender inequality have been made.
The highest grommet insertion rates are found in the highest social class12 160. In a Scottish study, rates, which varied fourfold across Scottish health regions, were negatively correlated with social deprivation167. In New Zealand, a study following a birth cohort for seven years found that children whose families were covered by health insurance were more likely to receive elective ENT surgery than those whose families were not172. Similarly, a U.S. study following 28,844 children aged less than 13 years who had at least one visit for otitis media found that continuous Medicaid enrolment increased the likelihood of surgery fourfold173. In
Canada the highest rates were also found in the areas of high socioeconomic status19.
Health insurance was again identified as a risk factor for grommet insertion in another U.S. study, with other risk factors being repeated ear infections, day-care centre attendance, White race and birth weight less than 1500g53. Children whose activity was reported as 'restricted'
54 had a far higher rate of grommet insertion than other children (44/1000 compared with
11/1000)168. Other factors that might underpin high rates of surgery have been suggested as the widespread introduction of audiometry, greater recognition of the presence of fluid in the middle ear by general practitioners, more otolaryngologists, antibiotics to treat postoperative infections and technical advances in tympanostomy tubes18.
The health beliefs, attitudes and behaviour of families also influence the surgical decision.
One case-control study compared parents of 142 children who had undergone myringotomy with parents of children who had not. The parents of children who had had surgery were more likely to label their children's middle ear disease as glue ear rather than recurrent AOM, and to describe their children as having presented more developmental problems, and to be more conscious of health-promoting activities174. Better-educated Canadian parents have been found to be more likely to consult a physician than those with lower education20.
However, it is unknown whether there is any relationship between consultation and surgery.
Surgical intervention for glue ear is a major consumer of paediatric health resources and deserves to be closely monitored. Currently in NSW we do not know many of the key aspects of such surgery, such as
• whether rates of myringotomy vary by age and gender
• the age at which a child is most at risk of having myringotomy
• which gender is most at risk of myringotomy
• whether age and gender rates have changed over time
• what percentage of children having myringotomy or other types of ENT surgery have
private health insurance
55 • whether myringotomy rates vary geographically in NSW when limited to the paediatric
population
• whether the percentage of combined ENT procedures differs by age and gender
• whether the age and gender profile of combined procedures has changed over time
• whether children who have myringotomy use the same amount of other health services as
children who do not
• whether children who have myringotomy change their pattern of utilisation of health
services following surgery
• whether, if there is a service utilisation change following myringotomy, this differs by age
of child at time of surgery
56 TONSILLECTOMY AND ADENOIDECTOMY
What is tonsillectomy?
Tonsillectomy is the surgical removal of the palatine tonsils. The palatine tonsils are two almond-shaped masses of lymphoid tissue situated at the entrance to the pharynx, one on each side, below the palate and above the base of the tongue. Tonsils are relatively large in young children and decrease in size as the child grows older. Tonsils help protect the entrance to the throat, trapping and destroying micro-organisms. They are a part of the immune system, producing antibodies.
Tonsillectomy is performed under general anaesthetic in hospital. It is increasingly being performed as a day case, rather than as a stay of overnight or longer. In most cases surgery is performed by a specialist, although this is not a requirement and occasionally the surgery is performed by a general practitioner.
Why is tonsillectomy performed?
Tonsillectomy is performed to relieve frequent or chronic episodes of tonsillitis and its sequelae. Tonsillitis, that is, inflammation of the tonsils, is caused by a viral infection or infection with streptococcal bacteria. Symptoms of tonsillitis are sore throat, difficulty in swallowing, headache, swollen glands and high fever14. In very young children, symptoms can be abdominal pain, vomiting and diarrhoea.
Untreated, tonsillitis can spread to surrounding tissues, causing peritonsillar abscess (quinsy).
Tonsillitis can also lead to rheumatic fever through a reaction of the immune system to the streptococcal organism.
57
Tonsillectomy is also performed to relieve episodes of sleep apnoea caused by partial respiratory obstruction due to enlarged tonsils (tonsillar hypertrophy) or adenoids14 36 175 176.
Obstructive sleep apnoea syndrome (OSAS) is a disorder of breathing during sleep characterised by prolonged partial upper airway obstruction and/or intermittent complete obstruction that disrupts normal ventilation during sleep and normal sleep patterns16.
Symptoms include habitual snoring, disturbed sleep and daytime behavioural problems and, uncommonly in children, daytime sleepiness. It can lead to neurodevelopmental abnormalities, growth retardation and cardiorespiratory failure177. The primary treatment for childhood OSAS is adenotonsillectomy175.
Prevalence and incidence of tonsillitis and OSAS
Tonsillitis occurs commonly in early childhood. In Australia in 2000/01, among children aged
0-14 years, tonsillitis was managed at 6% of general practitioner consultations51.
OSAS occurs in children of all ages, but is thought to be most common in preschool-aged children, the age when the tonsils and adenoids are largest relative to the airway size. Three studies identified by the American Academy of Pediatrics showed prevalence rates of OSAS to be 2% among preschool-aged children, and rates of habitual snoring 3% to 12%16. A study of 895 Italian children showed that 79.3% were non-snorers, 15.8% were occasional snorers and 4.9% habitual snorers178. When only counting habitual snorers who consented to nocturnal polygraphic monitoring and were diagnosed with OSAS, the prevalence in this
Italian cohort was 1%. However, if the 5 children, whose worsening symptoms had led to the performance of adenotonsillectomy, and the 2 children, who did not consent to further tests
58 despite their home-based oximetry results eligibility, are included, then the population prevalence of OSAS of these children aged under 12 years was 1.8%. A German review of
OSAS concluded that, at ages 2 to 6 years, every tenth child is a snorer, but that only one in five snorers (2%) has a severe upper airway obstruction179. Such a prevalence agrees with the findings of a Spanish review of the syndrome (1%-3%)180.
Natural history of tonsillitis and OSAS
With appropriate antibiotic treatment, acute tonsillitis usually resolves within two to three weeks. However, one study has shown that, among 623 Spanish children on waiting lists for tonsillectomy due to repeated episodes of tonsillitis, after an average waiting time of 10.8 months, most (81.4%) still required surgery because no spontaneous resolution of the clinical indications had occurred181.
The natural history of treated and untreated OSAS has not been delineated.
Management of tonsillitis and tonsillar hypertrophy
Tonsillitis caused by streptococcal infection is usually treated with antibiotics for a long enough period to ensure eradication of the infection, while treatment of viral tonsillitis is directed toward relief of symptoms. For both types an analgesic may be prescribed to relieve the pain. High fluid intake to prevent dehydration and soft foods are usually recommended.
Surgery is not usually indicated unless complications arise.
There is a lack of scientifically based guidelines regarding the efficacy of tonsillectomy and adenoidectomy182 and no consistent clinical pathway for the management of recurrent
59 tonsillitis183. In Australia in 1982, the National Health and Medical Research Council
(NHMRC) published guidelines for tonsillectomy and adenoidectomy14, which have been republished184 but to date have not been superseded. As at 20/11/2001 the NHMRC was not in the process of developing new guidelines (Personal communication, Appendix 1). The
1982 NHMRC guidelines gave the following indications for tonsillectomy:
1. repeated attacks of tonsillitis
2. airway obstruction
3. chronic tonsillitis
4. peritonsillar abscess
The criterion for the first indication, repeated attacks of tonsillitis, is three to five attacks of physician-diagnosed acute tonsillitis per year for two or more years. Doctors should also consider the severity of attacks, response to treatment, occurrence of complications and effect on general health and school attendance. Many histories of recurrent throat infection lack documentation and do not fulfil the above criteria: only 17% of 65 children with such histories were observed in the following year to have episodes conforming to tonsillectomy criteria185. However, a separate systematic review identified the frequency of recurrent throat infection as an indication for tonsillectomy as at least 7 documented infections in the previous year, or five per year for 2 years or 3 per year for 3 years, exhibiting at least one of the 4 following clinical criteria: oral temperature higher than 38.3º C, cervical lymphadenopathy of more than 2 cm, pus visible on the tonsils, a throat culture positive for Streptococcus 130.
The second NHMRC14 indication, airway obstruction, is signalled by loud snoring during sleep with intermittent obstructive apnoeic episode (OSAS). OSAS can have serious
60 consequences. Difficulty swallowing, hyponasal voice, daytime sleepiness, headaches, failure to thrive, pulmonary hypertension and right heart failure can be caused by airway obstruction175. The link between OSAS and poor growth has been suggested as being due to increased caloric expenditure during sleep186. Neurocognitive deficits, such as poor learning and attention deficit hyperactivity disorder, may be caused by hypoxemia or sleep fragmentation. In one small study of 16 children, those whose sleep was restricted for a single night were found to have impairment of the higher cognitive functions, such as verbal creativity and abstract thinking187. While confirmed OSAS is an indication for surgery, partial airway obstruction is less clearly defined. No association between snoring /sleep disturbance and recurrent episodes of tonsillitis has been found188.
The other two NHMRC indications for tonsillectomy are rare in children. Chronic tonsillitis is rarely a paediatric problem, and the incidence of peritonsillar abscess has decreased due to antibiotics. The latter are two of four indications for tonsillectomy proposed by Bluestone in
1992 – the other two are recurrent acute tonsillitis and tonsillar hypertrophy189.
International guidelines vary in the stringency of their criteria for surgery. The American
Academy of Otolaryngology – Head and Neck Surgery gave clinical indications for tonsillectomy and adenoidectomy as 3 or more infections of the tonsils and/or adenoids per year despite adequate medical therapy and hypertrophy causing upper airway obstruction
(sleep apnoea), severe dysphagia (trouble swallowing), sleep disorders or cardiopulmonary complications, as well as other rare indications17. According to the Italian National Program for Clinical Practice Guidelines, indications for tonsillectomy are at least 5 documented bacterial episodes that prevent normal functioning, only after an additional observation period
61 of at least 6 months. Adenotonsillectomy is recommended in children with significant apnoea, clinically confirmed, or, if doubtful, confirmed by polysomnography126. Recommended surgical criteria of the Finnish Medical Society are recurrent, confirmed bacterial tonsillitis
(more than 4 episodes per year), with dates and results of bacterial cultures to be included in the referral, or airway obstruction caused by tonsils, sleep apnoea or disorder of dental occlusion190. The Scottish Intercollegiate Guidelines Network set criteria for tonsillectomy as
5 or more episodes of tonsillitis per year, disabling symptoms for at least a year, and a 6- month period of watchful waiting191.
Airway obstruction (OSAS) is an important indication for tonsillectomy, and the American
Academy of Pediatrics has produced a guideline for its diagnosis and management 16.
Diagnosis of OSAS on a clinical basis through history taking and physical examination, although a common method, is not recommended, as it has been shown to be unable to reliably distinguish between OSAS and primary snoring16 175 192 193. Similarly size of the tonsils and adenoids alone do not indicate the presence of OSAS. Polysomnography is recommended as the diagnostic test of choice, as it is the only method that quantifies ventilatory and sleep abnormalities. Quantification, i.e., assessment of the severity of OSAS, is useful for determining treatment and follow-up.
The American Academy of Pediatrics guideline recommends adenotonsillectomy as the first line of treatment of reliably diagnosed OSAS. For those who prefer non-surgical alternatives, continuous positive airway pressure (CPAP), an electronic device that delivers constant air pressure via a nasal mask, is recommended as a second choice. However, CPAP has the drawback of needing to be used indefinitely. While the effectiveness of treating OSAS with
62 nasal steroids has been demonstrated in a selected sample of patients194, its applicability to a general population has been queried, as well as the risk of deleterious effects from its long- term use195.
In 2002 a review of clinical trials of adenotonsillectomy was undertaken by otolaryngologists to provide an evidence basis for the surgical decision196. They reported that good clinical evidence is available and provided the following indications. For adenotonsillectomy absolute indications are: adenotonsillar hyperplasia with OSAS, failure to thrive or abnormal dentofacial growth; suspicion of malignant disease; and haemorrhagic tonsillitis. Relative indications for adenotonsillectomy are: adenotonsillar hyperplasia with upper airway obstruction, dysphagia, or speech impairment, and halitosis. Relative indications for adenoidectomy are otitis media and recurrent or chronic rhinosinusitis or adenoiditis. Relative indications for tonsillectomy are recurrent or chronic pharyngotonsillitis, peritonsillar abscess, and streptococcal carriage.
What is adenoidectomy?
Adenoidectomy is the surgical removal of the adenoids, performed in hospital under general anaesthetic. The adenoids are pads of lymphatic tissue situated at the back of the nasal passage. Adenoids are relatively large in young children. The function of the adenoids is to trap and destroy bacteria that enter the body through the nose and help the body build up immunity to future infections.
63 Why is adenoidectomy performed?
Adenoidectomy is usually performed to alleviate obstruction of the nasal passage due to enlarged adenoids (hypertrophy). Obstruction can cause difficulty breathing, breathing through the mouth, hyponasal voice and snoring, as well as potentially dangerous episodes of sleep apnoea, daytime sleepiness and failure to thrive.
Obstruction can also cause build up of mucus in the nasal passage, leading to a runny nose during the day or cough when the child lies down. It can also block the Eustachian tubes leading from the nasal passage to the middle ears, with a possible result of ear infection and loss of hearing. Adenoidectomy is sometimes performed as a treatment for such middle ear disease.
Management of adenoid hypertrophy and infection
The 1982 NHMRC guidelines for tonsillectomy and adenoidectomy are non-specific with regard to the role of adenoidectomy. According to these guidelines, adenoidectomy is
"usually" performed with tonsillectomy following repeated attacks of acute tonsillitis. In the case of airway obstruction by tonsils, where adenoids contribute to the obstruction, removal of the adenoids is also necessary.
These guidelines give the indications for adenoidectomy as:
1. Adenoid hypertrophy. It is recommended that adenoid hypertrophy (large adenoids) be
detected with a pharyngeal mirror, an endoscope, an x-ray or by palpation under
anaesthesia.
64 2. Adenoid infection. Adenoid infection is defined as persistent mucopurulent discharge
caused by infected adenoids, but not nasal discharge caused by allergy, rhinitis or
infection of paranasal sinuses.
With regard to middle ear disease, the guidelines state that "glue ear" is not a sufficient indication for routine adenoidectomy, as the role of adenoidectomy in recurrent middle ear infection is not well defined. Other indications for adenoidectomy need to be present.
According to the American Academy of Otolaryngology – Head and Neck Surgery, adenoidectomy should not be performed with the insertion of the first set of tympanostomy tubes, but only with repeat surgery for chronic OME17, a position supported by the Italian
National Guideline Program126.
Incidence of tonsillectomy and adenoidectomy and population prevalence
Since historically tonsillectomy and adenoidectomy have often been performed in combination (adenotonsillectomy), their incidence and prevalence rates often overlap and will be considered together. Tonsillectomy is a major consumer of resources. In the U.S. in 1987 tonsillectomies were reported as the most frequent procedure performed on children under age
15166. Tonsillectomy is reported as the second most common operation undertaken in children in the U.K.183, and in 1992 it accounted for about 20% of all operations performed by otolaryngologists in Scottish hospitals197.
Tonsillectomy is a well-established procedure with a long history. Prior to the discovery and widespread use of antibiotics, severe attacks and complications of tonsillitis were common, and tonsillectomy became widely performed and almost commonplace. Data (numbers but
65 not rates) presented by Black160 show that, as early as 1919, 48,327 tonsillectomies were performed among English and Welsh children attending State-maintained schools. In the
1930s the removal of tonsils and adenoids peaked, with 105,284 tonsillectomies being performed among the same population of children in 1930-1932, before settling at over
77,000 in the 1940s. After that era, the popularity of the procedure declined. By 1967 in
England and Wales the tonsillectomy rate was reported as 12/1,000 children aged under 15 years160. Freeman in the U.S. in 1970 reported rates of 10.0, 23.1 and 7.7 per thousand children aged 0-4, 5-8 and 9-14 years respectively, equivalent to 12.6 for ages 0-14198. High incidences are reflected in high prevalences, and evidence of the high rates prevailing around the year 1970 is the extremely high tonsillectomy prevalence rate of 44% found among white
South African schoolchildren aged 16-18 years in 1981199. These children would have been aged 6-8 years, peak ages for tonsillectomy, in 1971, when the procedure would probably have been performed.
Attitudes toward the performance of tonsillectomy changed further in the late 1960s and early
1970s. In an analysis of tonsillectomy and/or adenoidectomy between 1971 and 1975
Canadian researchers found that only 32% met the recommended indications for surgery (3 -
5 episodes per year for 2 or more years)200, and suggested that audit alone would be sufficient to effect reductions. After that time, prevailing medical opinion changed as to the value of the procedure. This change in opinion, accelerated by parents' awareness of the change, led to tonsillectomy becoming less popular167, and rates declined worldwide.
In England and Wales the rate of tonsillectomy declined rapidly after 1967, levelling in 1975 at about 7.0/1,000 children aged 0-14 years160. In the U.S the tonsillectomy rate declined
66 from 12.6/1,000 children aged 0-14 years in 1970 to 8.1/1000 in 1977 (these rates are based on the published figures, but adjusted for comparison)198. U.S. tonsillectomy and adenoidectomy rates continued to decrease between 1978 and 1986166 201. In Scotland rates dropped from 7.8 children aged 0-15 years in 1975 to 6.0/1,000 in 1990167, with a further decline reported between 1986 and 1996197. In Poland the rate of tonsillectomy for persons of all ages dropped from 1.45/1,000 to 0.98/1,000 between 1961 and 1985202. In NSW, although far higher than Poland, rates of tonsillectomy and adenoidectomy dropped from 4.3/1,000 persons of all ages in 1978 to 1.4/1,000 in 1983203.
Very little is known about the level of tonsillectomy rates after 1987, although in the U.S. a decline between 1989 and 1991 was reported204. In Canada in 1990/91 the average rate was reported as 7.7 per 1000 children aged 1-14 years, which can be computed as 7.2/1000 children aged 0-14 years, assuming near zero incidence at age 07. In NSW on the other hand, the tonsillectomy rate was found to have increased from 5.1 per 1000 children aged 0-14 years in 1986 to 5.3/1000 in 1989/90, while adenoidectomy also increased, from 5.6/1000 children aged 0-14 years in 1986 to 6.3/1000 in 1989/90163.
Despite the importance of tonsillectomy and adenoidectomy as common paediatric surgical procedures, there is little scrutiny of trends. In NSW, the most populous state of Australia, we do not know:
• the rate of tonsillectomy or adenoidectomy among the paediatric population
• the long-term trends in tonsillectomy rates
• the long-term trends in adenoidectomy rates
67 Variation in rates of tonsillectomy and adenoidectomy
Wide geographical variation in rates of tonsillectomy has been found in many countries. In the U.K. between 1975 and 1980 rates of tonsillectomy were reported as varying considerably among health districts18. Variation in tonsillectomy rates was also found among 15 Scottish health boards in 1990167. In Canada in 1990/91, the relatively high rate of tonsillectomy in the province of Saskatchewan (8.85 per 1000 children aged 1 to 14 years compared with the average, 7.7/1000) prompted the publication of guidelines7. In NSW the tonsillectomy and adenoidectomy rates for all ages show considerable regional variation170. Hence area of residence must be considered a risk factor for tonsillectomy and adenoidectomy, and several theories as to the cause of this have been suggested. Possible sources of variation in rates of surgery based on geographic areas include variation in clinical judgment and prevailing custom, and variation in patient demand or expectation. Surgical variation may also reflect differences in population morbidity, due to living conditions or deprivation167 or even climatic factors, or differences in supply factors such as manpower, hospital bed provision, funding and waiting lists18.
Social class has been found to be a factor, but has operated in different ways over time. A
Scottish study found that, while middle class children had higher rates in the 1950s, 60s and
70s, this situation was reversed in 1990, with socially disadvantaged children more likely to have tonsillectomy167. This finding agrees with other studies cited by the researchers which showed that tonsillectomies for upper class children became less popular when parents became aware of changes in medical opinion, that is, that the operation offered few benefits except for carefully selected children. In keeping with this social class explanation is the finding mentioned earlier, that children with private medical insurance (and hence most
68 probably of higher social class) had higher rates of ENT surgery172. Another related social factor which has also been found to affect the performance of surgery is racial grouping: In the U.S. in 2001 the prevalence of tonsillectomy and/or adenoidectomy was 6.9% among
Black children under 18 years compared with 13.6% among non-Black children205. In the
U.K. a large study comparing children awaiting tonsillectomy with controls found no effect of social class on the number of sore throat and tonsillitis episodes, but a family tendency toward allergic reaction and parental tonsillectomy were predictive206.
There are also child-based factors. The likelihood of having tonsillectomy and/or adenoidectomy varies by gender. In Finland, males were found to predominate in the first ten years of age and females in the second125. In 1977 in the U.S., Freeman et al also found the predominance of females aged 9-19 years198. (Although examination of their raw rates suggests a predominance of males under 4 years, this was not found to be statistically significant.) In NSW in 1986 and 1989/90 Close also found more females aged 10-15 years had tonsillectomy163.
Age is another factor. In attempting to identify reasons for the high rates of tonsillectomy in
Saskatchewan, it was noted that outside large urban centres it was not uncommon for extremely young children, aged 2 or 3 years, to have surgery7. Concern over this led to guidelines being aimed especially at providing advice regarding the performance of tonsillectomy on very young children
Currently we do not know which of these risk factors are applicable to the NSW paediatric population. In particular we do not know in NSW:
69 • whether there is a particular age at which children are most at risk of having
tonsillectomy and adenoidectomy
• which gender is most at risk of having tonsillectomy and adenoidectomy
• whether there have been trends in age and gender rates over time
Debate regarding tonsillectomy and adenoidectomy
In 1979 Paradise outlined the nature of the controversy over the efficacy of tonsillectomy and adenoidectomy207, for which there is a lack of convincing evidence. The surgical decision is commonly made on the basis of attitudes and beliefs regarding its value, negative in the case of paediatricians and positive in the case of otolaryngologists, rather than on evidence.
Paradise expressed the hope that studies being undertaken would result in the reduction of uncertainty regarding the role of these procedures in the management of childhood respiratory disorders. However, two decades later the decision as to which individuals should receive surgery remains controversial. In Saskatchewan, Canada, a working group including otolaryngologists and paediatricians found that because it may be difficult to diagnose tonsillitis in patients under 5 years of age, some children may be undergoing surgery based wholly or in part upon recurrent non-specific viral URTI7. Among Dutch ENT surgeons and
GPs recurrent tonsillitis, enlarged tonsils and tonsillar crypt debris were considered the most important criteria for surgery208. In the U.S., Paradise et al found a modest benefit conferred by tonsillectomy on children who were only moderately affected with recurrent throat infection, which appeared not to outweigh the risks of surgery209. Despite surgical advances and the precision of the current operation, tonsillectomy is not a minor procedure2. Great skill and concentration are needed to meet unforeseen circumstances that might arise during the operation, for instance, adverse anaesthetic events.
70 The greatest risk during or following surgery is haemorrhage. A U.K. review of 352 children who had undergone tonsillectomy as day-case patients found that 0.6% suffered haemorrhage210. A similar U.S. study of 134 day-case patients found 1.6% experienced primary bleeding and 8.2% of these children were admitted as inpatients due to respiratory compromise211. Prospective patient eligibility for day-case (adeno)tonsillectomy has been set as low as 27% in one Scottish study, with 40% failing the medical criteria due to sleep apnoea or asthma and 39% on social grounds212. Another study that included adenoidectomy found that haemorrhage occurred in 3.9% of children213. Dehydration is another problem. Vomiting occurs regularly in the 48 hours following tonsillectomy: 11% of Japanese children suffered vomiting in the first 24 hours following surgery, and 29% in the next 24 hour period, compared with 7% of children administered a new type of drug214. Postoperative pain is well documented and significant, and techniques have been developed in an attempt to reduce it.
Pain lasts an average 8 days215 and can last up to 10 days216. Normal food intake can be interrupted for over a week after the operation217. Parents suffer considerable anxiety and need support and advice. The child can suffer psychological trauma and normal activity such as schooling is interrupted. Lastly, the economic implications are considerable.
A reduction in disease post-surgery is one benefit claimed for tonsillectomy. One non- randomised study which compared 66 children who had adenotonsillectomy with 34 who initially presenting with similar symptoms but were treated medically, reported a reduction in the annual number of "inflammatory pharyngotonsillar episodes", sore throat, nasal respiratory obstruction and middle ear disease in the surgery group seven years after surgery218. Another earlier (1978) study using Canadian health insurance claims data found that tonsillectomy saved between one and one and a half episodes of respiratory illness per
71 patient in the two years following surgery, but produce only a slight reduction in total medical claims219. There is anecdotal evidence of improved development and quality of life after surgery. In the Scottish tonsillectomy audit, 98% of patients (or their parents) were glad that the operation had been performed197, as were 88% of patients in a 1997 audit in England and
Wales220. One study of caregivers of children with obstructive sleep disorders found significant improvement in rated quality of life following adenotonsillectomy221, while another small study (13 children) found not only respiratory improvement following surgery, but increases in serum insulin-like growth factor –I levels and weight222. However, this study was too small for definitive conclusions. Another small prospective study found no change in caregivers’ assessment of children’s behavioural and emotional problems following adenotonsillectomy223, while a larger study did find an improvement224.
Physicians have become increasingly aware of the serious effects of sleep apnoea, which has become a significant indication for tonsillectomy, rising from 0% in 1978 to 19% in 1986201
225. In the U.K. in 1996, one in eight tonsillectomies was performed for obstructive symptoms130, and in The Netherlands, among 349 children listed for such surgery, OSAS was considered the indication by 11% of surgeons and 4% of GPs208. In contrast, for 134 U.S. children who underwent tonsillectomy between November 1995 and July 1997, OSAS was the primary indication for surgery211. While the effectiveness of (adeno)tonsillectomy has been established for obstructive sleep apnoea193 226 or frequent recurrent tonsillitis, in the
Netherlands only 35% of children who had the procedure satisfied one of these criteria182.
Adenotonsillar hypertrophy is implicated in OSAS227. Among Turkish schoolchildren aged 6-
13 years, the prevalence of tonsillar hypertrophy was found to be 11%, and an association was found between tonsillar size and snoring, mouth breathing and observed apnoea during sleep
72 and frequent upper airway infections228. In Finland Mattila, finding tonsillar hyperplasia to be the most frequent reason for tonsillectomy among children younger than 10 years, called for defined indications for pre-school age children, the most frequent recipients of surgery125. In
Italy for most (97%) of 166 very young children (less than 3 years of age) who had tonsillectomy, the criteria for surgery were obstructive sleep problems, history of snoring, eating and swallowing disorders229. In April 2002, the American Academy of Pediatrics issued guidelines recommending diagnosis of OSAS to be made polysomnographically rather than clinically15. In Spain also, an appeal was made for the diagnosis of OSAS to be made definitively, using polysomnography, rather than clinically176. A paediatric polysomnogram is believed to be the only means of providing objective evaluation of a child’s sleep status230.
Certainly several studies have demonstrated a poor correlation between clinical and polysomnographic evaluation of OSAS175 192 193. One typical study of 82 children with snoring or witnessed apnoeas found confirmation of OSAS by polysomnography in only 30% of these children231. Yet such evidence of the failure to find objective confirmation of OSAS has been criticised on the basis that the polysomnographic threshold is applicable to adults rather than children. The feasibility of the routine use of polysomnography has also been questioned192.
Messner argues that to make such an expensive assessment prior to surgery mandatory for all children with obstructive symptoms would be to deny treatment to those with no access to polysomnography.
While most children experience improved breathing following adenotonsillectomy227, surgery does not always correct OSAS – more severe cases in particular may experience residual disease230, and in such cases children may be referred postoperatively for continuous positive airways pressure therapy232. Children who undergo tonsillectomy and adenoidectomy may
73 have silent apnoea after surgery230. In a U.S. study of 577 children who had undergone tonsillectomy, 35% were diagnosed as having OSAS compared with only 13.7% of children who had not had surgery205.
The benefits of tonsillectomy remain controversial. In NSW we need to obtain a clear idea of the reasons for performing tonsillectomy, whether guidelines are followed, and whether surgery has an impact on subsequent use of health services. Specifically, we need to discover
• what diagnoses are recorded for tonsillectomy
• whether diagnoses have changed over time in line with guideline recommendations and
whether OSAS has become a significant diagnosis
• the proportion of children who have had polysomnography prior to tonsillectomy
• whether children who had tonsillectomy had the minimum number of episodes in period
prior to surgery as recommended by the guidelines as an indicator for surgery
• whether children who had tonsillectomy or adenoidectomy used the same amount of
health services as children who did not
• whether the pattern of health service utilisation changed following tonsillectomy
• whether, if there was a change in use of health services following tonsillectomy, this
differed by age of child at time of surgery
74 NEED FOR CLINICAL PRACTICE GUIDELINES
Paediatric ENT surgery is an example of the general class of elective surgery where a need for more consistency is evident. As has been seen, its epidemiology is characterised by considerable variation in rates, both geographical and over time. Such variation may not be easily accounted for by differences in patient and illness characteristics233. While in some cases, such as mastoiditis or other serious conditions, surgery is clearly called for, the appropriate level of ENT surgery remains unknown, and the amount of variation suggests that some unnecessary surgery does occur. Unnecessary surgery is surgery that does not demonstrate clear cost-benefit superiority over other forms of treatment or no treatment at all.
Unnecessary surgery wastes scarce health care resources, causes financial burden, can cause unwanted sequelae such as pain and complications, and may even endanger the life of the patient.
The types of ENT surgery that form the subject of the current program of research, that is, tonsillectomy, adenoidectomy and myringotomy, are generally performed at the discretion of the physician in preference to other forms of treatment for non-life-threatening conditions. It is crucial that the judgement of the physician, upon whom the performance of elective surgery depends, be well informed and in accordance with the principles of current best practice. In the case of tonsillectomy, little consensus between general practitioners, paediatricians and otolaryngologists regarding indications for and benefits of tonsillectomy has been found, and there is no consistent clinical pathway for the management of recurrent tonsillitis183. Clinical practice guidelines (CPGs) aim to provide guidance, limit unnecessary surgery, reduce physician uncertainty and achieve consistent best practice in the treatment of conditions where elective surgery is an option.
75
However, variation can arise from factors other than uncertainty or lack of consensus.
Geographical variation, both within and between countries, has been correlated with economic factors234 and distribution of resources, such as medical manpower, operating facilities and hospital bed availability235. Within the same country there may be differential access to medical resources, for example, an undersupply of surgeons in rural areas, or the cost of the procedure may exclude certain demographic groups236. In such cases, it is low rates that should be of concern. While international variation is often considered to reflect the availability and affordability of health care in each country, one study comparing the incidence of common surgical procedures found that, while overall rates were higher in some countries than others, the degree of variability within each country was similar, and there was consistency among countries in the rank order of variability of specific procedures237. This finding argued for similar degrees of controversy among physicians regarding indications for these procedures
Similarly, secular variation, that is, variation over time, can result from several factors other than lack of consensus. New knowledge of indications for and benefits of surgery can lead to an increase over time, while provision of expert guidelines and evidence of contraindications can lead to a decrease. Health service interventions, such as changes in payment systems or new treatments or drugs, can affect surgery rates. Variation can also reflect differences or changes in population morbidity. However, researchers who assessed the contribution of population characteristics to interregional variation in surgery rates failed to find a correlation between high rates and ill health in two studies8 238.
76 Other than where such reasons for variation are identifiable, it is generally thought that variation arises from physicians' differing beliefs with regard to the value (needs and benefits) of the procedure18. According to Wennberg and Gittelsohn, variation is largely due to differences between doctors in diagnosis, indications for surgical variation and their belief in the value of therapy239. Paradise holds that, among the paediatric population, indications for tonsillectomy and adenoidectomy vary from being clearly indicated in only a small percentage to clearly not indicated in the majority and questionable in the rest207. The decision to perform surgery on those in the questionable group depends upon the judgement of the physician. There is long-standing recognition of a high degree of professional uncertainty about the clinical indications for tonsillectomy18. However, Black found even greater regional variation for myringotomy than tonsillectomy rates among the same U.K. populations. He concluded that, since tonsillectomy was a longer-established procedure with presumably less likelihood of uncertainty than myringotomy, the amount of variation could be regarded as an index of uncertainty.
Hence conflicting attitudes and beliefs of individual practitioners are seen as a major factor in unexplained variation. Paradise in 1979 described prevailing medical opinions regarding tonsillectomy and adenoidectomy as being polarised and made a plea for professional attitudes to become more critical, open-minded and enquiring207. Black in 1984 described the rate of surgery for glue ear as an "epidemic" that owed its popularity to fashion rather than science160.
Guidelines do not address the issue of population morbidity. Patients can also be a source of variation. Their beliefs with regard to the value of the procedure may vary, and their
77 expectations can influence physicians. In this regard, it is significant that one U.K. study found a history of parental tonsillectomy to be predictive of children’s placement on a waiting list for tonsillectomy206. It can be hypothesised that the parent’s own experience influenced and normalised the expectation of surgery in their children. Another predictive factor found in this study was a family history of atopy.
Unexplained variation and the use of interventions inappropriately or before their effectiveness has been established have been major factors in the development of clinical practice guidelines240. Yet, in the case of ENT surgery, there still exists a dearth of guidelines regarding tonsillectomy and adenoidectomy182.
In NSW, we do not know whether variation in paediatric ENT procedures, a pre-condition for the assumption of clinical uncertainty, occurs. Specifically, we do not know
• whether myringotomy varies geographically in NSW when limited to the paediatric
population
• whether tonsillectomy varies geographically in NSW when limited to the paediatric
population
• whether the geographical variation of tonsillectomy in NSW is of the same magnitude as
that of myringotomy
What are clinical practice guidelines?
Clinical practice guidelines (CPGs) have been defined as systematically developed statements to assist practitioner and patient decisions about appropriate care for specified clinical outcomes241 242.
78
However, this definition has been criticised as leaving open many questions, including the objectives of the guidelines, their source and the value placed on this source233 243.
What is the aim of CPGs?
The aim of guidelines is to improve the quality of health care and its accessibility, appropriateness, effectiveness, efficiency, safety and acceptability, and provider competence244, as well as to reduce practice variation and improve health outcomes.
However, CPGs are also seen as a means of directing scarce resources away from inefficient and towards efficient services245, or of lowering costs. This aim has led to fears that guidelines may be perceived as simply tools for reducing the cost of health care and freeing clinical practice from the threat of litigation240 244. Guidelines are mistrusted when their aim is seen as standardisation of practice and reduction of medical liability246, or as a means of limiting access to secondary care rather than assisting clinician decision-making247. It is undisputed that physician decisions not only influence the health of their patients, but also determine the cost of their care248. Hence the influence of practice has the potential to control health care expenditure, as in a study of breast cancer care, where Minter reported that adherence to guidelines did reduce cost without adversely affecting survival or quality of care249.
Some believe that, rather than decreasing costs, CPGs may actually increase costs240 250. In one study of radiography for the lower lumbar spine, Russell found that if CPGs had been followed, more would have been performed251. Guidelines that advocate expensive tests and
79 treatments and may be of high quality can frustrate the efforts of those who wish to control expenditures, such as managed care organisations252. Guidelines that trim costs, reduce average length of hospital stay and increase efficiency may be more attractive to such agencies to the potential detriment of the patient.
Hence at the outset of CPG formulation, an ethical problem exists. While there is a universal need to contain health care expenditures241, the conflicting needs and motivations of physicians, patients and society as a whole need to be taken into account253. Larson supports a role for the public in sharing and limiting resources254. Some economic approaches to setting priorities for CPG development require the assignment of values to competing medical interventions and outcomes in the realisation that health resources are finite. These economic models use optimisation techniques to determine the maximum improvement in population health through adoption of specified treatment recommendations. Such models require quantification of these treatment benefits. One cost effectiveness model is based upon estimates of average years of life gained255. Another model requires, for each adverse clinical event, the quantification of the treatment effect, the point at which benefit exceeds cost, and the number of patients needed to prevent the event256. These models aim to make the process of selection of topic for guideline development transparent and defensible in terms of optimal population benefit.
Thomson has developed a series of questions to aid in the choice of topic for which CPG development is desirable. Topics should be chosen on the basis of their importance in terms of process and outcome of patient care, high volume, cost or risk and unexplained practice variation, and whether the investment of time and money in development is likely to be repaid
80 through change that benefits patients and can be implemented257. Unexplained practice variation that is wide and persistent is almost certainly evidence of troublesome quality and accessibility problems258, and can make patients anxious about their care259. In Canada a guideline advisory committee formed in 1997 has produced criteria for prioritisation of topics for guideline development that take into account the incidence and cost of the problem, variation, evidence that current best practice guidelines are not being followed and requests from clinicians or organisations for guidelines260. Inappropriate, variable or unwanted health practices should be of sufficient magnitude that an interventional study could cause or detect improvement261. Guidelines should contain a succinct statement of their objectives, including the targeted health problem, targeted patients and providers and the main reason for developing recommendations, which should differ from prevailing practices.
The reason ENT surgery has been the topic of guideline development and dissemination in several countries is that it displays most of the above characteristics. There is concern that varying amounts of unnecessary surgery is being performed. The guidelines attempt to remove as far as possible the subjective element in determining the surgical threshold.
What factors influence the acceptability of CPGs?
The guideline development group
The choice of development group is critical for acceptance. Who developed, funded and endorsed the CPG should be stated explicitly261. The developers must have credibility with a peer group of professionals. Specialty societies must play a central role262. However, CPGs produced exclusively by a specialty society or single profession may be acceptable only in the short term. If CPGs affect resource allocation or other public policy decisions, there will be
81 pressures to include representatives of the public and other interested parties in the development group. Parents who participated in a conference felt that they should have access to important sources of information relevant to the care of their children and that parental involvement in the development and dissemination of guidelines was vital233. Yet too wide an inclusion base can cause difficulties. In developing otitis media guidelines, the
American Academy of Pediatrics in association with the American Academy of Family
Physicians, the American Academy of Otolaryngology - Head and Neck Surgery, and the
Department of Pediatric Otolaryngology at the University of Pittsburgh all involved their members in the process, and found time and geographical distance to be problems263.
It is important to avoid conflict of interest, whether real or perceived. Organisations can find it difficult to serve both their members' and the public's interest because CPGs can affect members' incomes. Most guidelines published in peer-reviewed medical literature between
1985 and 1997 were produced by subspecialty (45%) or general (33%) medical societies, with
16% produced by government agencies and the remaining 6% by miscellaneous groups264.
Guidelines developed by parties with commercial interests, such as pharmaceutical firms, or those developed with the aim of cost reduction, for example by health insurers or managed care organisations, are seen as lacking credibility233. Ratatansky considers it the ethical responsibility of the physician to ensure that rates of payment for capitated patients are sufficient to provide adequate care265.
Local involvement in development is considered vital for adoption of recommendations247 254
266 267. Effective CPGs almost invariably have a local champion with credibility and influence in the community. To achieve maximum impact, the development of CPGs at hospital level,
82 with the participation of medical staff, pharmacists and administration, has even been advocated268. Yet the paradoxical result of local involvement can be a plethora of almost identical guidelines. Multiple guidelines on the same topic are confusing and can lead to selective adoption of practices that reflect physician preferences and prejudices258. Worrall estimated that in Canada in 1997 there were at least 2500 CPGs available269. A plethora of competing guidelines on breast imaging compelled the American College of Radiology to publish their own more authoritative guidelines270. Most recommendations of 45 U.K. depression guidelines tended to reflect the joint consensus statement produced by the Royal
College of General Practitioners and Royal College of Psychiatrists, with differences in style and presentation271. Local clinicians are urged to concentrate on effective dissemination and implementation strategies, rather than on creation of new guidelines. Guidelines should not conflict with other or previous guidelines and reasons for differing recommendations should be given.
Such proliferation of guidelines is of concern233 250 258. It can defy the ability of clinicians to have knowledge of a guideline's existence, let alone an understanding of its content248. Hibble and colleagues, following anecdotal evidence that general practitioners in the U.K were being flooded with guidelines, surveyed all guidelines in general practice in the Cambridge and
Huntingdon Health Authority272. They found 855 guidelines, which, when piled up, reached a height of 68cms. They conclude that these guidelines are inaccessible, unmanageable and unusable, and that their "exponential" growth is creating a "Tower of Babel".
83 Basis of recommendations
CPGs should empower clinicians to make informed decisions and counter managerial pressures to adopt sub-optimal practices248. They can do so only to the extent that they are evidence-based. Their definition of proper care should rest on the critical evaluation of evidence, rather than on expert opinion273. Randomised controlled trials are considered to represent the highest quality of scientific evidence and expert opinion the lowest246 274.
Guidelines developed by such bodies as the American Academy of Pediatricians or the
Agency for Health Care Policy and Research are considered of high methodological quality with regard to evidence233. However, while CPGs claim to be basing recommendations on well-designed clinical studies, they often fail to describe how the evidence was collected and evaluated and the results translated into recommendations252. A review of 279 published
CPGs found only 16.8% specified methods of identification of evidence, 14.3% the time period from which data was collected and only 7.5% used formal methods such as meta- analysis to combine results264. A review of drug therapy CPGs quoted by Lewis found both the sources of information on which evidence was based and methods for rating evidence unsatisfactory in over 80% of the reviewed CPGs258.
While it is desirable that CPGs be supported by high quality evidence, in practice such evidence is often lacking252 275. What evidence there is may be of poor quality or result from non-randomised controlled trials. The necessary research may be totally absent. This may leave developers with no option but to rely on expert medical opinion. Bergman reports that researchers at the RAND Corporation found, when reviewing guidelines for paediatric conditions, that only 11% of evidence came from randomised controlled trials, with 72%
84 coming from expert opinion, 10% from clinical panels and 11% from non-randomised controlled trials. (The sum of these quoted percentages exceed 100)246.
Physician attitude
A major barrier to the acceptance of guidelines is the perception that they threaten physician autonomy240 253 276. Physicians believe CPGs will make medical practice less satisfying248, are over-simplified and too rigid for individual patients240. Physicians may disagree with or distrust recommendations, preferring to rely on their own experience or that of their colleagues277. Recommendations can be se seen as challenging their professional judgments278 or appearing to compromise patient care. There is concern that the existing process of diagnosis as unstructured problem solving and decision making under conditions of uncertainty is being threatened250. Practitioners believe that medicine is only partly a science, while the rest is inspired judgement, hunch and the application of skill and knowledge262.
They are concerned that CPGs may be applied coercively rather than allowing flexibility in applying recommendations to each patient's unique needs244 279.
Opinions regarding recommendations are often influenced by personal biases from clinical experience and training252. One New Zealand study found substantial and durable individual practice styles (writing prescriptions, ordering tests or x-rays, and follow-up visits) in primary medical care280.
Psychosocial factors - ways in which groups interact, make decisions and achieve consensus - are important and often neglected281. Lewis maintains that medical sociology - group
85 attitudes and behaviours, value-laden assessments of research and guideline feasibility - governs the fate of CPGs. Values and interests greatly influence CPG acceptance262.
Another barrier to acceptance is self-interest - physician concern over how recommendations will affect reimbursement252 262 277.
Yet another barrier to acceptance is concern over the possible use of CPGs in litigation, and this concern is probably justified. In the Netherlands, although not regarded as legal rules,
CPGs play various roles in judicial decision-making282. In the U.S., Dans reports that guideline development was incorporated into federal legislation in 1994, and that lawyers and third-party payers are ready to use the proliferating guidelines against doctors283. Harpwood has explored the legal consequences of ignoring guidelines, and urges clinicians to take the initiative in developing guidelines before they are pre-empted by managers and employers and their clinical freedom is lost284.
A contrary view is that, while CPGs may limit a clinician's freedom of choice, they may protect them against malpractice claims and unreasonable patient expectations285.
Dissemination strategy
In their review of 59 guidelines that were evaluated for effectiveness, Grimshaw and Russell found the dissemination and implementation strategy to be of major importance286. The probability of a guideline's being effective was maximised when its development involved those to whom it was targeted, and its dissemination was via specific educational intervention.
The greater the educational component of dissemination, the greater the likelihood of
86 recommendations being accepted into practice. U.K. general practitioners preferred having guidelines posted to them and being able to discuss them in seminars. They least preferred publication in a medical journal. Other studies have found that dissemination via mailing targeted groups yields below average effectiveness, with journal publication being the least effective method of dissemination250 287.
Bergman asserts and Haines agrees that a model of the diffusion of innovations first proposed
50 years ago by Everett Rogers288 applies to the dissemination of CPGs246 289. Under this model, the time taken for new technology to be disseminated to the ordinary user is 6 to 10 years. The initiating groups in the dissemination process are the innovators. They are followed by the early adopters, who look outside their group or institution for new and innovative practices. The early adopters convince the early majority to try new technology.
Finally, widespread adoption by the early adopters convinces the late majority to try the new practice. The final group is the non-responders, who will only adopt the practice when mandated. Hence the presentation of practice guidelines to a group of physicians without first working with the early adopters and the early majority is more likely to fail.
Implementation strategy
Changing practice needs local support systems259 266 268, including clinical audit programs and feedback of information on current practice. Bergman advocates using guidelines with a set of outcome and performance measures that provide feedback to clinicians and allow for modification to meet the needs of local populations246. Greco likewise advocates changing practice through feedback, such as average length of stay and number of medications and tests277. However, first physicians must recognise that current practices need improvement
87 and be able to respond. Health policy makers may regard research as irrelevant. Attitude change among health professionals and managers may be needed for them to accept analysis of their own activities. Haines favours giving patients information to effect change 289.
Rothschild believes inertia to be a major factor in failure to implement CPGs276, while, according to Grayson, lack of time is a barrier290. Some of the best quality, evidence-based, objective CPGs are too long and burdensome for the average family physician260. They must be user-friendly, and may need to be reformatted and summarised. The difference between researchers and innovators who promote CPGs and their targets may affect the adoption of the innovation289.
How effective are CPGs?
Effect on process of care
CPGs are rarely systematically evaluated243. Physicians claim to be influenced by CPGs. In one Australian review 42% of neonatologists and 35% of obstetricians claimed to have changed their practice291. Such claims might be exaggerated. Wright found that, while 90% of optometrists claimed to have received guidelines and 57% to have read them, there was actually only a non-significant change in the recommended direction from 74.5% to 81.5% of new patients treated292.
Grimshaw and Russell found that 55 out of 59 evaluated guidelines produced change in the process of care in the direction recommended by the guideline286, and an Edinburgh study found publication of the Scottish Intercollegiate Network guidelines on indications for tonsillectomy191 resulted in improved adherence to recommended criteria293. In Australia,
88 following publication of National Health and Medical Research Council (NHMRC) guidelines for diabetic retinopathy, McCarty reported significant change in the treatment for macular oedema, but no change in fluoroscan angiography294. By contrast, Rosser maintains that few CPGs have demonstrated any effect on clinical practice in Ontario287, while in the
U.S. only 18% of 1513 surveyed physicians said their practice had changed due to guidelines240.
Heffner believes that, although guidelines improve process and outcome of patient care, the effect is sometimes slight and not always lasting248. Dans reported that only 11% of practitioners were familiar with guidelines issued 2 years earlier283, while in the U.K. Hill found a 40% increase in appropriate dermatology referrals following guidelines was not sustained 2 years later295. Kendrick similarly reports that the benefits of depression education faded after 2 years213.
Effect on patient outcome
Most evaluations of CPGs examine the process of clinical care rather than the patient outcome. Worrall found that, of 91 studies of the effects of CPGs on primary care, only 35 concerned clinical care , while the rest concerned preventive or investigative medicine269. Of the 35 concerning clinical care, only 13 reported on clinical outcomes and, of these, only 5 reported significant improvement in patient outcome. Worrall concludes that there is little evidence that CPGs are effective in improving patient outcomes in primary care.
In the American College of Practitioners survey mentioned earlier, 16% of internists reported that guidelines had a major effect on their practice240. However, fewer internists reported
89 being influenced by guidelines than by colleagues, medical textbooks or continuing medical education.
This failure to produce an effect may not be attributable to the CPG. The potential effect of
CPGs cannot be properly assessed until they are developed and delivered to maximise their acceptance261. The health outcomes expected need to be clearly specified and quantifiable256
261 267. Shekelle reported that specific guidelines for low electrodiagnostic tests in low back pain led to more appropriate ordering of tests than non-specific or profile guidelines296. While the CPG should convince that benefits outweigh harms and costs, if the treatment effect is imprecise, the recommendations cannot be strong274. Shaneyfelt found that only 40% of 279 guidelines he studied specified the outcome of interest, despite their being developed to improve patient outcomes264.
Potential effectiveness of NSW guidelines for paediatric ENT surgery
Before attempting to evaluate the effect of the 1982 guidelines for tonsillectomy and adenoidectomy and the 1993 myringotomy guidelines on rates of paediatric ENT surgery, their potential for effectiveness needs to be assessed in terms of the foregoing criteria.
Was the development group respected and acceptable?
The Health Care Committee Expert Panel on Child Health of the NHMRC developed the
1982 tonsillectomy and adenoidectomy guidelines. The NHMRC is the foremost medical council in Australia. It advises the Australian community and Commonwealth and State governments on standards of individual and public health, and supports research to improve those standards. The myringotomy guidelines were developed by the NSW Health
90 Department, using a panel representing the Australian College of Paediatrics, the
Audiological Society of Australia, the Australian Society of Otolaryngology, Head and Neck
Surgery, the Child and Family Health Nurses Association and the Royal Australian College of
General Practitioners, as well as medical officers of the Department.
Both development groups ought to have been respected and acceptable to the medical community. However, both sets of guidelines were government initiatives, rather than having been produced by professional otolaryngologic groups.
Were the recommendations based on evidence?
The basis of the tonsillectomy and adenoidectomy guidelines appears to rely upon expert opinion, while, in the case of the (later) myringotomy guidelines, in addition to expert opinion, a comprehensive literature review was undertaken.
Were the recommendations clear and unambiguous?
The 1982 tonsillectomy and adenoidectomy guidelines are clear with regard to criteria for surgery in cases of repeated attacks of acute tonsillitis. However some of the indications for surgery with regard to airway obstruction would rely upon subjective reports from parents of snoring with intermittent apnoeic episodes, swallowing, headaches and failure to thrive. They do not delineate criteria for distinguishing between obstruction and partial obstruction of the airways. Adenoids are stated to "sometimes" contribute to the obstruction, and their removal is "usually" necessary. There is a large element of subjective judgement in this recommendation. With regard to adenoidectomy recommendations are clear with regard to hypertrophy (yet how large is too large is left to the judgement of the physician) and infection.
91 In the case of middle ear disease, the guidelines say that the role of adenoidectomy is "not well defined” and "probably" not justified. Again, there is large scope for subjective judgement.
The management summaries of the 1993 guidelines for myringotomy are clear and unambiguous and presented in concise, flowchart form. However the text on the management of OME simply says that medical management in the form of an appropriate antimicrobial agent should precede surgical intervention. It does not specify the period, as the summaries do. It goes on to say that "if medical management fails, the decision whether to watch and wait or surgically intervene will depend on an assessment of factors" identified in the text. In other words, subjective assessment.
If the surgical decision relies on subjective judgment, it follows that two children with identical symptoms could be treated differently. The one child might have surgery while the other does not.
Was the outcome of interest clearly specified?
In the guidelines for tonsillectomy and adenoidectomy, the outcome was implied rather than specified. Indications for surgery were outlined, and possible morbidity and mortality resulting from surgery implied that unnecessary surgery should be avoided. In the myringotomy guidelines, although caution and "watchful waiting" was advised in the (rather long) text, there was no summary stressing the preferable duration of such waiting and alternative treatment before proceeding to surgery.
92 Was the most effective dissemination strategy employed?
The tonsillectomy and adenoidectomy guidelines were disseminated widely as an official publication. The myringotomy guidelines were published in The Medical Journal of Australia as a Supplement. Hence both strategies were sub-optimal. This is supported by a finding of
Blogg, who conducted an evaluation of the myringotomy guidelines among health professionals297. She found that 67% of ENT specialists, 54% of paediatricians and 41% of audiometrists reported receiving the guidelines, while only 21% of audiologists and 18% of
GPs had received a copy.
Was the most effective implementation strategy employed?
Publication was the only means of implementation - again sub-optimal.
How acceptable to physicians were the myringotomy guidelines?
Blogg found that, of those who received a copy of the guidelines, most agreed with the recommendations in general. However, when questioned on particular aspects of the recommendations, agreement varied by type of practitioner. Significantly more GPs (54%) disagreed with the recommendations to wait and watch than either ENT specialists (32%) or paediatricians (35%). This is an important finding in view of the gate keeping role of the GP.
When asked about their agreement with "the use of adenoidectomy if other strategies fail or compliance is a problem" (not the wording of the guidelines, which only state that adenoidectomy may confer benefit in the presence of enlarged adenoids), more ENT specialists (72%) than paediatricians (36%) or GPs (43%) agreed.
93 Nevertheless, bearing the above limitations in mind, there are questions that need to be asked regarding the efficacy of guidelines in NSW.
We need to know
• whether dissemination of the 1982 guidelines was effective in reducing tonsillectomy or
adenoidectomy rates
• whether dissemination of the 1993 myringotomy guidelines was effective in reducing
myringotomy rates
94 CONCLUSION
In conclusion, despite ENT surgery being an area of child health of great importance, to date little systematic monitoring of levels of surgery or trends has taken place in NSW. There has been no objective evaluation of the impact of guidelines on the incidence of surgery or of the extent of compliance with guideline recommendations. No research into the children who have these therapeutic interventions has been undertaken, nor into whether their consulting behaviour prior to surgery could suggest a possible reason for its performance, and, if so, whether surgery produced a change. There has been no analysis of the economic impact of
ENT surgery on the health system and on the population. This thesis addresses these issues.
The major research questions addressed in this thesis are:
1. What is the level of NSW ENT surgery rates and their trends over time, and how
compatible are these rates with international rates?
2. Did guideline dissemination in NSW affect the rate of surgery and have guideline
recommendations been followed?
3. Prior to surgery, did children who had surgery use more health services than those
who did not have surgery?
4. If so, did surgery result in decreased use of services?
5. What is the impact of ENT surgery on the health system (utilisation of hospital
resources and costs to Medicare)?
Many significant gaps in current knowledge have been outlined in this Chapter, and questions identifying these gaps have been identified. The questions raised have all been addressed in
95 this program of research. In Table 1.1 these questions have been placed under the headings of major aims, together with Chapters where the relevant results can be found.
96 Table 1.1 Questions addressed in the current program of research and relevant results chapters
Research questions Results chapters What is the level of NSW ENT surgery rates?
1. What is the rate of myringotomy among the NSW paediatric population? Chapter 3
2. What is the rate of tonsillectomy or adenoidectomy among the NSW Chapter 3 paediatric population? 3. Do rates of myringotomy in NSW vary by age and gender? Chapter 3
4. At what age is a NSW child most at risk of having myringotomy? Chapter 3
5. Which gender is most at risk of myringotomy? Chapter 3
6. At what age are NSW children most at risk of having tonsillectomy and Chapter 3 adenoidectomy? 7. Which gender is most at risk of having tonsillectomy and adenoidectomy? Chapter 3
8. Do myringotomy rates vary geographically in NSW when limited to the Chapter 3 paediatric population? 9. Do tonsillectomy and adenoidectomy rates vary geographically in NSW Chapter 3 when limited to the paediatric population? 10. Do tonsillectomy rates in NSW vary geographically to the same extent as Chapter 3 myringotomy rates? What are the trends in ENT surgery rates over time?
1. What are the trends in NSW myringotomy rates over time? Chapter 3
2. What are the trends in tonsillectomy rates over time? Chapter 3
3. What are the trends in adenoidectomy rates over time? Chapter 3
4. Have age and gender rates of myringotomy changed over time? Chapter 3
5. Have age and gender rates of tonsillectomy and adenoidectomy changed Chapter 3 over time? 6. Has the incidence of acute otitis media, a frequent precursor of OME, Chapter 3 increased in NSW? Did guideline dissemination in NSW affect the rate of surgery and were guideline recommendations followed? 1. Was dissemination of the 1982 guidelines effective in reducing Chapter 4 tonsillectomy or adenoidectomy rates in NSW? 2. Was dissemination of the 1993 myringotomy guidelines effective in Chapter 4 reducing myringotomy rates in NSW? 3. Did children who had myringotomy show evidence of 'watchful waiting' as Chapter 10 recommended by the 1993 NSW guidelines? 4. Did children whose reason for having myringotomy was hearing loss have a Chapter 10 hearing test prior to surgery, as recommended in the 1993 NSW guidelines? 5. Did the diagnosis recorded for children having myringotomy reflect Chapter 4 guideline recommendations? 6. What proportion of children having myringotomy had a hearing test Chapter 10 following surgery? 97 7. What diagnoses were recorded for tonsillectomy? Chapter 4
8. Have tonsillectomy diagnoses changed over time to reflect guidelines? Chapter 4
9. What proportion of children having tonsillectomy had polysomnography? Chapter 10
10. Did children who had tonsillectomy have the minimum number of episodes Chapter 10 in period prior to surgery recommended by the guidelines as an indicator for surgery? 11. What percentage of myringotomy procedures were performed in Chapter 3 combination with adenoidectomy or tonsillectomy? 12. Does the percentage of combined procedures in NSW differ by age and Chapter 3 gender? 13. Have the procedure combinations changed over time? Chapter 3
14. Has the age and gender combined procedure profile changed over time? Chapter 3
Prior to surgery, did children who had surgery use more health services than those who did not have surgery? 1. What health services outside the hospital setting did the NSW paediatric Chapter 6 population use between birth and 8 years of age? 2. What health services outside the hospital setting did the cohort subgroup of Chapter 7 children who had ENT surgery use between birth and 8 years of age? 3. Did children who had ENT surgery use the same amount of health services Chapter 8 as children who had no ENT surgery? 4. Did children who had myringotomy use the same amount of health services Chapter 8 as children who had no ENT surgery? 5. Did children who had tonsillectomy or adenoidectomy use the same amount Chapter 8 of health services as children who had no ENT surgery? 6. Did the amount of health service utilisation by children who had ENT Chapter 12 surgery vary by age at time of surgery? If so, did surgery result in decreased use of services?
1. Did the pattern of health service utilisation change following myringotomy? Chapter 12
2. If there was a change in service utilisation change following myringotomy, Chapter 12 did this differ by age of child at time of surgery? 3. Did the pattern of health service utilisation among children having Chapter 12 tonsillectomy change following surgery? 4. If there was a change in service utilisation change following tonsillectomy, Chapter 12 did this differ by age of child at time of surgery? What is the impact of ENT surgery on the health system?
1. What proportion of paediatric hospitalisation among NSW children is due to Chapter 3 ENT procedures? 2. What proportion of NSW children having ENT surgery has private health Chapter 3 insurance? 3. What is the cost to Medicare of paediatric ENT surgery, including Chapter 13 perisurgery costs? 4. If children who have ENT surgery use above average amount of services, Chapter 13 what is the extra cost to Medicare?
98 CHAPTER 2 EPIDEMIOLOGY OF ENT SURGERY IN NSW: INTRODUCTION & METHODS
This chapter provides the background to and methods used in a descriptive study into ENT
surgery rates among NSW children and trends in these rates during the period January 1981
to June 1999.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions background & methods & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 13 Chapter Chapter 7 ENT Economic cohort impact: utilisation: Results & Results & discussion discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
99 INTRODUCTION
Despite ENT surgery being a major consumer of paediatric hospital resources, the epidemiology of ENT surgery among children in NSW has never been comprehensively examined. While, as part of the NSW Health Department's consistent interest in elective surgery rates, rate variation among the health areas and regions is assessed and published annually170, these standardised ratios are averages and refer to all ages rather than being child- specific. No trend analyses are undertaken, gender- and age-specific rates remain unknown, and only two of the ENT procedures, tonsillectomy and myringotomy, are reported on. The number of these procedures performed in combination with each other or adenoidectomy remains unknown, as does the population rate for ENT surgery as a whole. It is important that such rates and trends be established so as to determine whether Australian practice is in line with best practice and trends in other countries.
One previous analysis was undertaken, but it covered only a limited period, 1986 to
1989/90163. This investigation found an increase in rates of ENT surgery from 9.8 to 11.8 per
1000 children. The major contributor to this increased rate was myringotomy, although rates of both tonsillectomy and adenoidectomy had also risen. Concern over this finding prompted the NSW Health Department to form an expert Working Party to develop consensus guidelines for the management of paediatric middle ear disease13. The stated aim of these guidelines was to provide a framework for the development of management guidelines by individual primary care practitioners. It can be hypothesized that the unstated aim of the
Working Party was to reduce practitioner uncertainty regarding the surgical threshold for myringotomy, with the implicit expectation that reduction of uncertainty would result in a reduced rate of surgery. However, despite the effort and resources employed in producing
100 and disseminating these myringotomy guidelines in 1993, subsequent rates have not been tracked to determine whether the guidelines have had any effect. Attempts to understand or stem the increase found in the other two ENT procedures, tonsillectomy and adenoidectomy, have not been made.
ENT surgery is elective surgery. Beliefs regarding the perceived benefit of this surgery vary.
Although parental or other pressure may play an important role, the clinician is the arbiter of the decision to intervene surgically. Hence rates of elective surgery reflect clinician attitudes and behaviour regarding surgical thresholds. Along with supply of surgeons and surgical facilities and the monetary self-interest of surgeons, clinician uncertainty is a major factor in the geographical variation in surgery rates found in Australia and internationally18 163. It is unknown to what extent clinician attitudes and beliefs are evidence-based. While studies of these attitudes have not taken place, the effects of such attitudes on behaviour are reflected in surgery rates. Rates reflect the attitudes prevailing among the clinical community during relevant periods. Paediatric elective surgery is a serious issue. If physician attitudes towards such surgery are to be considered to represent more than fashion, it is important that as many determinants of surgery as possible be identified.
In the following section the epidemiological profile of paediatric ENT surgery in NSW over a long period is determined for the first time. Such surgery impacts considerably on health system resources and on the children exposed to this surgery, yet neither the rate at which it is occurring nor the trends in such rates in NSW is currently known. The determination of rates of surgical interventions can allow comparison with other states and countries, while the possible detection of inter-regional differences can stimulate research into their causes. It is
101 also unknown whether the characteristics of the patient population have changed over time, which could suggest changes in indications and clinical practice.
ENT surgery is an extremely important area of child health and a major consumer of resources. Establishment of the fundamental epidemiology of ENT paediatric surgery in NSW is seen as essential in providing a benchmark against which future trends can be measured. In the current section of the research, the incidence of ENT surgery among NSW children over a number of years is comprehensively described. Specifically, the following were determined:
• rates of myringotomy, tonsillectomy and adenoidectomy among the NSW paediatric
population
• trends in these rates between January 1981 and July 1999
• geographical variation in surgery rates
• age- and gender-specific rates
• trends in age- and gender-specific rates between January 1981 and July 1999
• the amount of ENT surgery performed in combination with another ENT procedure
• trends in combination proportions between January 1981 and July 1999
102 METHODS
Definition of terms
In the context of the current study, the definition of terms used is as follows:
• Paediatric Aged under 15 years
• Myringotomy Myringotomy with or without insertion of tympanostomy tube
• ENT surgery Tonsillectomy, adenoidectomy, or myringotomy with or without
insertion of tympanostomy tube, or any combination of these procedures
Study design
The study design was a retrospective examination of hospital administrative records of all
NSW children who had undergone ENT surgery between January 1981 and June 1999.
Data source
The study sample was drawn from the New South Wales (NSW) Health Department’s
Inpatient Statistics Collection (ISC). NSW is the most populous state of Australia, which has a national health insurance system, Medicare, which allows close to universal access to health care in the form of remuneration of 85% of the scheduled cost of medical services (since 2004
85% - 100%) and access to inpatient care as a public patient in a public hospital. The NSW
Health Department has maintained the ISC, a comprehensive data collection, since the mid-
1970s. All hospital inpatient separations (episodes of patient care) are recorded for mainly administrative purposes. The ISC dataset contains information on the diagnoses and procedures relevant to every episode of inpatient care in all approved public, private, psychiatric and repatriation hospitals and public nursing homes in NSW. The ISC also includes data on separations of NSW residents from public and private Queensland hospitals, public Victorian and public Australian Capital Territory hospitals by arrangement with these
(bordering) States. The ISC holds approximately 1.8 million records per year.
103
Confidentiality of these data is protected by the custodian, the NSW Health Department.
Application was made to the Statewide Health Confidentiality and Ethics Committee for access to the data, and, following modification of the request, the Committee granted limited access to specified record fields, subject to security and confidentiality guarantees (Appendix
2). Ethics approval to conduct this program of research was obtained from the Human Ethics
Committee, The University of Sydney, Reference No. 99/01/38.
Hospitals submit data, coded and edited by hospital staff, mostly on computer tape, or on written forms coded by Health Department staff. Prior to 1981 the pool of hospitals submitting data was not comprehensive, but there has been full coverage of NSW hospitals since that date. Data from some hospitals (mostly those providing written data and having less than 1500 separations per year) were initially included in the ISC on a rotational sampling basis (usually two months in five). The proportion of data in the ISC which came from sampled hospitals diminished over time, from approximately 30% of the data in 1983 to less than 10% in June 1993. Sampling factors were applied to these data. Since July 1993, full enumeration from all hospitals has occurred. Protocols exist and are applied in the NSW
Health Department to independently check the comprehensiveness and accuracy of data supplied.
The ISC reporting period is one year. The collection, which is subject to regular audit checks by NSW Health Dept., currently holds approximately 2 million records per year. The first year in which all NSW hospitals were covered was 1981. In 1982 the ISC data were considered poor and not used. The 1983 data were judged to be reliable, but in 1984 a
104 doctor's strike occurred in NSW, which affected rates of hospitalisation and surgery in 1984 and 1985, and therefore data from these years is considered to be non-representative. The
1986 data are generally considered to be a good benchmark year. After 1986, the reporting year changed from calendar to financial year. The quality of reporting in the first year of the change, 1987/88, was considered too poor to be usable. Since that date all ISC years have been considered accurate and reliable.
The ISC record contains administrative and clinical fields (Example: Appendix 3). The clinical fields contain information on patient diagnosis and procedures performed, recorded initially on the ISC form by the attending medical practitioner. Health information managers either in the hospital or at the data collection centre then code this information in accordance with international protocols. This clinical coding was performed according to the
International Classification of Procedures in Medicine (ICPM)298 in 1981, 1983 and 1986, according to the International Classification of Diseases Clinical Modification (9th revision;
ICD9-CM) Volumes 1-3299 from 1988/89 to 1997/98 and according to the International
Classification of Diseases and Related Health Problems 10th Revision Australian Modification
(ICD10-AM)300 in 1998/99. There is allowance for the insertion of several diagnosis and procedure codes on the ISC record. Until 1991/92 up to four diagnosis and four procedure codes could be entered on the ISC form. Since then the recording of up to ten codes each has been allowed.
Record selection
Records were selected for inclusion in the study if they fulfilled the following criteria:
• age of patient under 15 years
105 • area of residence of patient NSW, regardless of location of hospital. Non-NSW residents
treated in NSW hospitals were excluded
• any procedure field contained a code denoting an ENT surgical procedure, either
• myringotomy with or without insertion of tympanostomy tubes (ICD9-CM code
20.0, or, in 1981-1986, 5200)
• tonsillectomy (ICD9-CM code 28.2, previously 5281)
• tonsillectomy and adenoidectomy (ICD9-CM code 28.3, previously 5282)
• adenoidectomy (ICD9-CM code 28.6, previously 5285)
A total enumeration of persons whose records fulfilled the above criteria was obtained for the calendar years 1981, 1983 and 1986, and for each of the financial years 1988/89 to 1998/99 inclusive. Permission was granted by the Statewide Health Confidentiality and Ethics
Committee (Appendix 2) to extract from each of the above ISC records the following fields considered relevant to this study:
• Age of patient (in months)
• Gender of patient
• Area of residence of patient
• Diagnosis (all those recorded)
• Procedure (all those recorded)
• Length of hospital stay
• Same day flag - Hospital stays of longer than four hours are designated as admissions.
Where a patient is admitted and discharged on the same day, length of stay is recorded as
one day. A flag is inserted to distinguish such same day stays from overnight stays, also
recorded as one day. 106 • Financial status - paying or non-paying patient. Due to a change in terminology a
misunderstanding occurred in the data request, and the information in this field was only
valid for the years 1989/90 to 1993/94 and 1997/98 and 1998/99.
• Sample factor - a weighting factor assigned to each hospital not fully enumerated in the
ISC years prior to June 1992, and used to adjust counts to estimate actual activity.
Although there have been some changes to the ISC form over time, the core fields relevant to this study have not altered materially. This can be seen in the description of the analysis data files supplied by the NSW Health Department (1997/98 and 1998/99 data, supplied later, were identical to1996/97 data) (Appendix 4).
NSW paediatric population totals for five year age and gender groups and for single years of age for selected years were drawn from Australian Bureau of Statistics estimates for the years
June 1981 through to June 1999301.
Statistical analysis
Incidence and rate of ENT procedures
Frequencies (adjusted by sample factors where relevant) and crosstabulations by gender of child and five-year age group were obtained for each procedure for each year using the SAS statistical package302. A count was made for each procedure whether performed alone or in combination with one of the other procedures. Hence the sum of counts for tonsillectomy, adenoidectomy and myringotomy exceeds the count for any ENT procedure. Using population estimates relevant to each ISC year301, 5-year-age-group- and gender-specific rates per 100,000 children for each procedure were calculated. While tonsillectomy and adenoidectomy rates represent individual children, myringotomy rates could overstate the
107 number of children, due to the possibility that some might have been grommet re-insertions for the same child. To assess the number of combined procedures performed, frequencies of all possible combinations were obtained for each year.
Trends over time
The five-year age- and gender-specific rates were entered into Poisson regression models303
304 to test whether rates had changed over time and the influence of age and gender of child on any such change. The Poisson distribution is ideal for describing rates such as these, because it was developed by Poisson as the limiting form of the binomial distribution when n
305 tends to infinity and p tends to zero, while at the same time μ = np remains constant . In the case of these annual surgery rates, n is very large (the NSW child population), p is very small (the proportion of children undergoing surgery in any one year) and μ is constant (the number of children undergoing surgery in any one year). Poisson regression models summarise relative risk in the presence of possibly interacting covariates306. The dataset entered into each model consisted of counts of cases, classified by the exposure factor
(YEAR, ranging in value from 1 in 1981 and 18.5 in 1998/99) and age/gender covariates
(AGESEX, entered in the form of dummy variables representing six groups: 0-4 males, 0-4 females, 5-9 males, 5-9 females, 10-14 males, 10-14 females, with 0-4 males as the base group), together with the logarithm of the relevant population as the offset to the counts of procedures. Use of the logarithm of the population enabled significant effects to be expressed in terms of percentage change, rather than absolute amounts. A composite age/gender covariate was used rather than separate age and gender covariates because the gender differential was found to vary by age group. Owing to the large size of the dataset, statistical significance was set at p<0.01 throughout. 108
The models were set up as
COUNT = YEAR + AGESEX +AGESEX*YEAR
This model yielded a base 1981 proportion (rate), an estimate for the effect of YEAR which represented (where significant) the percentage by which the rate changed per year (trend), estimates for each AGESEX group (the difference between each group and the base group in year 1) and AGESEX*YEAR the interaction between year and age/gender group (any divergence from the YEAR effect by each of the age/gender groups).
This Poisson regression approach was used in preference to other time series methods because of the number of parameters of interest. This part of the study aimed at determining how rates behaved in each of the 3 ENT procedures in each of the 6 age/gender groups over the study periods, and the above method was able to provide a simple estimate for each of the 18 subgroups.
From results of these models, estimates of rates per 100,000 per year for each age and gender group were calculated. These estimates were compared graphically with the observed rates.
Risk of having surgery
To describe the cumulative risk of a NSW child having an ENT procedure by age 15 in certain years, cross-sectional lifetable methods307 were applied to incidence rates in selected years. Lifetables were constructed using incidences of surgery at each year of age for the ISC
109 years 1981, 1983, 1989/90 and 1998/99 and populations of children aged 0 years in the relevant year 301.
These tables were constructed by successively calculating for each year of age the proportion of the population that had not had surgery. Columns were drawn up with the following headings:
Agex, where x = 0 to 14 lx = population who have not had surgery, starting with population aged 0 qx = proportion of children aged x who had surgery before age x+1 (from observed incidences of surgery) dx = lx x qx lx+1 = lx - dx
The accumulation of the resulting qx proportions expressed the cumulative risk of surgery by each successive age. These risks are hypothetical projected risks, in that the age-related incidences of the year on which the lifetable is based are assumed to remain constant. Such cumulative risks were calculated in each of the years 1981, 1983, 1989/90 and 1998/99 and compared.
Changes in prevalence of surgery for children aged under 5 years
In this section in contrast with the cumulative risks of undergoing surgery calculated using lifetable methods, it was possible to calculate the actual prevalences of surgery at ages up to five years for successive cohorts of children in certain years. Because these ISC data for the years 1988/89 to 1998/99 completely enumerate all NSW children who had ENT surgery, rates in successive years chart the surgical experience of various cohorts of children as they
110 progressed in age from one year to the next. Hence the surgery rate of children aged under 1 year in 1988/89 refers to NSW children born in 1988/89, the rate for children aged 1 year in
1989/90 refers to the same 1988/89 birth cohort, and so on. The surgical experience at each year of age under 5 years was calculated in this way for seven such cohorts, children born in
1988/89 through 1994/95, using relevant population denominators for single years of age301.
Cumulative cohort rates were then calculated for each successive age under 5 years, thus obtaining the relevant prevalences of surgery. Prevalences of the 1988/89 birth cohort at each age were compared with the 1994/95 birth cohort’s prevalences.
Geographical variation
Owing to changed administrative boundaries, it was only possible to examine five of the study years for geographical variation in ENT rates. The years for which accurate Area populations were obtainable were 1988/89 – 1992/93, and these were the years examined. These Areas can be broadly grouped according to their geographical proximity to the centre of Sydney as
Inner Metropolitan, Outer Metropolitan and Rural. Areas in these broad geographical groups share other characteristics, such as population size and type of hospital facilities (Table 2.1).
111 Table 2.1 Broad geographical group and Area Health Service by population and presence of highest-ranking hospital Broad group Area Health Service Estimated Existence of population, 0-14 highest ranking yrs, June 1993 (Level 3) Hospital in Area? Inner Southern Sydney 102803 Yes Metropolitan Eastern Sydney 40899 Yes Central Sydney 47919 Yes Western Sydney 141621 Yes Northern Sydney 126816 Yes Outer Wentworth 76980 No Metropolitan South Western Sydney 172115 No Central Coast 56051 No Hunter 112779 Yes Illawarra 72233 No Rural Central West 42303 No South Eastern 40312 No North Coast 93054 No New England 62127 No Orana Far West 36997 No South Western 63899 No New South Wales 1288911
It can be seen in Table 2.1 that Areas designated Rural are sparsely populated and have no
Level 3 hospitals, while Areas designated Inner Metropolitan group are clustered around central Sydney, densely populated, and have high level hospitals.
The following map shows the administrative boundaries of the New South Wales Area Health
Services during the above period.
112
113 The area of residence analysis was performed using the method of indirect standardised ratios. The extent to which Areas varied in the performance of each procedure was determined by first calculating the State average procedure rate for each age and gender group. State age/gender- specific rate was then applied to the five-year age- and gender-specific population estimates relevant to each area. This process yielded the number of cases that would be expected in the area if it had experienced the same procedure rate as the State. The ratio of total observed cases to the number expected then produces the standardised ratio, a comparison of each area with the State average, adjusted for its size and age/gender profile.
The formula for the indirectly standardised ratio is 308
Standardised Ratio = total observed procedures for area x 100 total expected procedures for area
Statistical significance of departures from 100 (the State rate) was tested using the following formula.
Standard Error (SE) = 100 x (total observed procedures)1/2 Total expected procedures
Standardised Ratios and SEs were calculated for each procedure for each year, 1988/89 -
1992/93. Variation from the State average was considered significant at the 0.01 level.
To determine whether any variation found in Area procedure rates might represent chance rather than systematic variation, a variability index, V, was calculated for each procedure and each year309. V was derived from the following formula.
2 2 2 2 V = 1/n ∑iOi / Ei - 1/n (∑Oi/ Ei ) – 1/n(1 – 1/n) ∑iOi/ Ei
where i denotes Area and Oi are the number of observed ENT surgery separations and Ei are expected separations (hereafter designated admissions to avoid confusion.)
114 Confidence intervals were calculated for each V using the following formula for V2 (standard error of V).
2 2 2 2 V2 = ∑i (n -1) Oi / Ei -∑i 1/n(Oi/ Ei)
The interpretation of V is that it is the standard deviation of the standardised ratios, or the ratios corrected for the variation due to chance. If V2 is negative, this means there is no systematic variation. The higher the value of V, the greater is the amount of systematic area variation. Systematic variation was considered to be present if the lower limit of the 95% confidence interval was above zero.
Changes over time in proportional incidence of otitis media
Since otitis media is a frequent precursor of myringotomy, it was hypothesized that trends in surgery might reflect trends in otitis media among the NSW paediatric population in comparable periods. Accordingly, a request was made to Associate Professor Helena Britt,
Family Medicine Research Centre, University of Sydney, for a special analysis of data held by the Centre. In agreement with the Australian Institute of Health and Welfare, the Centre undertakes research involving the collection, collation, analysis and dissemination of statistics relating to characteristics of general practitioners in Australia, patients of general practitioners and the medical services and pharmaceutical prescriptions provided to them.
The special analysis compared the rate of diagnosis with otitis media among children who consulted a general practitioner in 1990/91 with that in 1998/99. The 1990/91 survey consisted of 495 randomly selected NSW family physicians who each recorded details of consultations during two one-week periods six months apart. In the 1998/99 survey 984 family physicians each recorded 100 consecutive consultations. Data were weighted for 115 physician caseload. From data subsets containing only children under 15 years and under 5 years, the percentage diagnosed with otitis media was determined for each year and rates compared. In this comparison, the statistical probability level was set at less than 0.05.
Advantages of the ISC data
1. Administrative data collection systems are a very much undervalued and underused
source of research. When used innovatively, they hold an important niche. The ISC
data, on which this descriptive epidemiological section of the study is based, are
comprehensive, reliable and valid.
2. They are comprehensive because the NSW Health Department which administers the
collection insists upon complete returns from every hospital in the State. The
Department has regular systems in place to check compliance, and also ensure that the
data are reliable. In the earlier years, a small amount of sampling of data took place
among some of the smaller hospitals, but after July 1993 there was complete
enumeration of hospital separations.
3. The period of this study is also comprehensive for NSW, covering every collection
year considered reliable between 1981 and 1998/99, the last year available at the time
of commencement of the study. There were 14 years of data examined, totalling
203,647 records.
4. The very commonness of the procedures studied ensures their validity. It is highly
unlikely that an error could occur in coding any of these procedures on to the patient
record. Hence a child coded as having had an ENT procedure would almost certainly
actually have had it.
116 Limitations of the data
1. These administrative data consist of unmatched records. While this analysis treats
rates as if they represent individuals, it is known that, in the case of myringotomy,
some cases may be the same children undergoing a repeat grommet insertion. Due to
such possible repeat procedures, rates of myringotomy and its risk may have been
overestimated.
2. Due to the boundaries of some administrative health areas having been changed by the
NSW Health Department over time, population data relating to the study health areas
was obtainable only for 5 ISC years. Hence only these years were tested for procedure
rate variation. However, standardised ratios were obtained for each of these years and
the presence of systematic variation in these ratios tested for. If the results showed
that systematic variation was present in each of the years tested, it could reasonably be
assumed that such variation is probably endemic to all the study years. The aim of this
part of the analysis was not to provide precise and comprehensive details of inter-area
variation, but simply to determine whether such variation existed. The establishment
of the presence of systematic variation could then be interpreted as one indication of
continuing uncertainty and controversy over the performance of these procedures.
117 Chapter 3 EPIDEMIOLOGY OF ENT SURGERY IN NSW: RESULTS & DISCUSSION
In this chapter, rates of ENT surgery for the NSW population of children aged under 15 years and their trends over the study period are determined and compared with international rates.
Age- and gender-specific rates, combinations of surgery and the extent of geographical rate variation are determined. The risk of these children having ENT surgery in selected years during the study period is quantified. A summary of these results has been published310
(Appendix 5).
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 4 Chapter 8 Chapter 10 Chapter 13 Research Introduction Introduction Introduction Introduction Conclusions background & methods & methods & methods & methods & aims
Chapter 3 Chapter 9 Chapter 5 Chapter 11 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 12 Chapter 4 Chapter 6 ENT Economic Effect of cohort impact: guidelines on utilisation: Results & rates Results & discussion discussion
Chapter 7 Comparison: ENT with total cohort: Results & discussion
118 RESULTS
The contribution of ENT surgery to hospital utilisation
In 1998/99 17647 children underwent ENT surgery. Table 3.1 shows the total number of children treated in hospital in this year and the proportion who had ENT surgery by age of child.
Table 3.1 Percentage of total hospital separations of NSW children due to ENT surgery by age of child, 1998/99
Age Total sep- ENT surgery Tonsillectomy Adenoidectomy Myringotomy arations Number % of Number % of Number % of Number % of total total total total 0 119282 332 0.3 3 0.0 11 0.0 325 0.3 1 21547 1337 6.2 119 0.6 221 1.0 1245 5.8 2 16053 1546 9.6 453 2.8 662 4.1 1158 7.2 3 14081 2102 15.0 891 6.3 1159 8.2 1370 9.7 4 12323 2440 19.8 1136 9.2 1352 11.0 1515 12.3 1-4 64004 7425 11.6 2599 4.1 3394 5.3 5288 8.3 5 11261 2386 21.2 1073 9.5 1280 11.4 1413 12.5 6 9425 1948 20.7 946 10.0 1044 11.1 1030 10.9 7 8267 1418 17.2 693 8.4 729 8.8 746 9.0 8 7566 1038 13.8 518 6.8 505 6.7 463 6.1 9 6662 814 12.2 445 6.7 427 6.4 303 4.5 5-9 43181 7604 17.6 3675 8.5 3985 9.2 3955 9.2 10 6147 590 9.6 357 5.8 325 5.3 196 3.2 11 6407 501 7.8 321 5.0 238 3.7 141 2.2 12 6681 445 6.7 299 4.5 203 3.0 96 1.4 13 7218 360 5.0 232 3.2 143 2.0 89 1.2 14 8366 370 4.4 274 3.3 113 1.4 66 0.8 10-14 34819 2266 6.5 1483 4.3 1022 2.9 588 1.7 1-14 142004 17295 12.2 7757 5.5 8401 5.9 9831 6.9 yrs
Age 0 years was excluded from the calculation because over 80,000 hospital separations of children of this age would refer to newborn infants. In 1998/99, separations due to ENT
119 procedures comprised 12.2% of total separations among children aged 1-14 years. Among children aged 5-9 years, ENT procedures accounted for 17.6% of all separations for this age group. In children aged 1-5 years, the greatest contributor to these proportions was myringotomy, while in the 5-9 age group, each of the three types of surgery contributed roughly equal proportions. Among children aged 10-14 years, the greatest proportion of ENT hospitalisations was due to tonsillectomy.
Type of hospital and insurance status
In 1998/99 most (55.5%) ENT procedures were performed in public hospitals. This contrasted with three earlier years, 1991/92 - 1993/94, where slightly more children were treated in private hospitals (53.0%, 52.5%, 54.2%). In these years 59.1%, 58.2%, and 56.8% of children who had an ENT procedure were insured or privately funded. By contrast, this percentage had declined by 1998/99 to only 33% of children being covered by insurance or privately funded, with 64% of those treated in private hospitals and only 7% treated in public hospitals being covered. In 1998/99 51.0% of children who had an ENT procedure were treated as day only patients.
Incidence of ENT procedures, 1981-1998/99
The number of NSW children aged under 15 years who had an ENT procedure in each of the study years and rates per 100,000 children are shown in Table 3.2.
120 Table 3.2 Number of NSW children aged 0-14 years who had an ENT procedure and rates/100,000 in each year, 1981 - 1998/99 Year Tonsillectomy Adenoidectomy Myringotomy ENT procedure No. Rate No. Rate No. Rate No. Rate /100,000 /100,000 /100,000 /100,000 1981 8066 634 9327 734 6555 516 14441 1136 1983 5156 405 6554 515 7971 626 13082 1027 1986 6230 495 6787 539 6931 550 13175 1046 1988/89 6303 501 7534 598 8494 675 14754 1172 1989/90 6939 550 8152 646 9836 780 16564 1313 1990/91 6944 549 8256 653 9464 749 16219 1283 1991/92 7156 563 8339 656 9256 728 16435 1292 1992/93 7414 578 8739 681 10419 812 17671 1377 1993/94 7093 550 8358 648 9798 760 16853 1308 1994/95 6623 511 7659 591 9574 739 15961 1232 1995/96 6903 529 7540 578 9031 692 15756 1208 1996/97 6173 471 7567 577 10187 777 16192 1234 1997/98 6975 530 8038 611 9843 748 16543 1257 1998/99 7760 590 8412 639 10156 772 17627 1340
In Table 3.2 the sum of numbers and rates for tonsillectomy, adenoidectomy and myringotomy exceed those for ENT due to combined procedures. Both numbers and rates for
ENT and for myringotomy appear to have increased over time, while the trends for tonsillectomy and adenoidectomy are not clear. These rates are illustrated in a following section (Figure 3.2).
International comparison
Very few international rates corresponding to the study years were available for comparison with NSW rates. In Table 3.3, for those years that do correspond, NSW rates, adjusted to the same scale of measurement, have been compared with published international rates.
121 Table 3.3 Tonsillectomy rates/1,000 children in NSW and internationally, 1961–1990
Year NSW U.S.: U.K. Poland Scotland 0-14yrs 0-14yrs 0-14yrs All ages202 0-15yrs167 (all ages) 203 (1)Freeman198(2) 160 Rosenfeld201 (3)Derkay166
1961 1.45 1962 1963 1964 1965 1966 1967 12.0 1968 1969 1970 12.6
1971 9.8
1972 9.5
1973 9.0
1974 8.5
1975 6.7 7.8 1976 35.7% 7.0 7.9 1 1977 8.1 7.9 dec 7.5 8.0
1978 (4.3) 6.9 6.5 6.0 66% 1979 6.1 6.7 5.5 dec 1980 5.7 7.0 5.6
1981 6.3 5.6 6.5
1982 (66.1% 5.2 4.0
1983 4.0 (1.4) dec) 5.4 5.6 1984 4.3 32% 6.0 32.1% 66% dec dec 1985 3.5 2 0.98 5.3 1986 4.9 3.4 dec 5.6 1987 3.0 62% 5.2 dec3 1988 11.2% 5.4 14.2% 1989 5.0 inc 5.5 inc 1990 5.5 6.0
Table 3.3 shows that tonsillectomy rates declined between 1961 and 1985 in all countries including NSW, where the rate (all ages) dropped by 66% between 1978 and 1983 203. This was very similar to the U.S. experience, where Rosenfeld reported a decrease between 1978 and 1986 of 66%201 and Derkay a decrease between 1977 and 1987 of 62%166 (Derkay’s data exclude same day facilities and military hospitals). After 1983, rates for children aged under
15 years began to increase in NSW, as did rates in Scotland. For those years that overlap the
122 period of the current study, the comparison between rates in NSW with rates in Scotland is illustrated in Figure 3.1, as well as showing the rate in Canada in 1990/91.
Figure 3.1 Comparison between NSW, Scottish and Canadian tonsillectomy
rates/1,000 children aged 0-14 years, 1981 - 1991.
9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 Rate per 1000Rate children 1.0 0.0 1981 1982 1983 1984 1985 1986 1987 88/89 89/90 90/91 Year
NSW Sco t lan d Canada
Figure 3.1 shows that tonsillectomy rates for children aged 0-14 years in NSW and Scotland between 1981 and 1991 were reasonably similar. However, both were lower than the 1990/91
Canadian rate of 7.77/1,000 children aged 1-14 years7, which, even after adjustment to ages 0-
14 years (assuming nil tonsillectomies under 1 year of age), remains higher at 7.2/1,000.
For myringotomy there were also few comparable international rates. One English rate quoted in the 1991 Effective Health Care bulletin was 5.0/1000 children, but this may have referred to an earlier year12. In comparison, the NSW rate for 1991/92 was higher at 7.3/1000 children under 15 years. Myringotomy rates in East Anglia/Oxford during the study period have been quoted for children aged 0-9 years 1. Hence NSW rates for this age group were calculated and are compared with East Anglia and Oxford rates in Table 3.4.
123 Table 3.4 Myringotomy rates/1,000 children in NSW and internationally, 1975–1991
Year NSW 0-9yrs East Anglia and The Netherlands 0- Scotland 0-15yrs Scotland Oxford 12yrs 164 167 (1975-1986)159 0-9yrs1 160 Canada (1996- 1999) 19 (0 - 14yrs) 1975 5.0 3.1 1976
1977
1978 1979 1980 8.7 74% inc
1981 7.2 10.0 1982 26.4% 11.7 increase 31.9% 1983 9.1 13.2 inc 1984 12.1
1985 11.8 60-fold 1986 7.9 13.2 increase 1987 12.79
1988 9.5 12.1
1989 11.0 11.8 297% 1990 10.4 11.5 16.8 9.2 inc 1991 10.2 12.2 4.8% 29.8% 44.3% dec inc 1992 11.4 increase 12.0 21.8 1993 10.7 10.6 6.0% 1994 10.6 9.2 20.5 dec
1995 9.9 8.4
1996 11.1 7.4 (Ave. 8.35)19 1997 10.6 6.8 43.0% dec 1998 10.9 1.7%inc 1999
Table 3.4 shows levels and trends in myringotomy rates. With regard to trends, until 1986 rates of myringotomy increased hugely in all countries including NSW, almost trebling in
England and Wales between 1967 and 1980160, more than doubling in East Anglia and Oxford between 1975 and 1986 and trebling in Scotland between 1975 and 1990 167 (although another report stated that rates in Scotland had increased sixty-fold between 1966 and 1986 159). After
124 1986, rates in East Anglia and Oxford started to decline, as they did in the Netherlands after
1992164. In contrast, NSW rates did not decline after 1986.
With regard to level, for children aged 0-14 myringotomy rates in NSW were higher than rates in Scotland in 1989/90 (7.8 compared with 4.7/1,000)167, but lower than average
Canadian rates in 1996-1999 (7.5 compared with 8.4/1,000)19 and also probably in 1997-2000
(average 1997-1999 NSW rate of 7.6/1,000 children aged 0-14 years compared with
11.1/1,000 Canadian children aged 0-15 years 169). The East Anglia/Oxford rates for children aged 0-9 years are the only international rates which cover a range of years overlapping those of the current study. The relative levels of these and the NSW rates differ according to period, as shown in Figure 3.2.
Figure 3.2 Myringotomy rates: NSW compared with East Anglia/Oxford.
140
120
100
80
60
40 20
Rate/1,000 aged0-9yrs children 0
1 8 5 982 83 85 87 989 90 92 94 97 198 1 19 1984 19 1986 19 198 1 19 1991 19 1993 19 199 1996 19 1998 Year
NSW East Anglia/Oxford
In Figure 3.2 it can be seen that, while myringotomy rates for NSW children aged 0-9 years were initially lower than rates in East Anglia/Oxford1, by 1989 they were approximately
125 similar and showed no sign of declining, in contrast with East Anglia/Oxford, where rates dropped quite sharply after 1992. Since these East Anglia/Oxford rates are also probably higher than rates for England and Wales in comparable years, having been higher between
1975 and 1980160, myringotomy rates in NSW since 1993 are most likely considerably higher than rates for the whole of England and Wales.
Lifetime risk of ENT surgery
The cumulative risk of NSW children having ENT surgery by age 15 years in 1981 was estimated using lifetable methodology, and compared with the cumulative risks in 1983,
1989/90 and 1998/99 (Table 3.5).
Table 3.5 Risk of NSW children having ENT surgery by age 15 years in 1981, 1983, 1989/90 and 1998/99
Year Tonsillectomy Adenoidectomy Myringotomy ENT surgery
1981 10.0% 11.6% 8.1% 17.9%
1983 6.2% 7.9% 9.6% 15.7%
1989/90 8.0% 9.4% 11.4% 19.2%
1998/99 8.9% 9.6% 11.6% 20.2%
Table 3.5 shows that initially, between 1981 and 1983, the risk of ENT surgery decreased from 17.9% to 15.7%, but then increased, passing the 1981 level by 1989/90, and by 1998/99 reached 20.2%. The risk of myringotomy increased throughout the study period, with the greatest increase occurring between 1983 and 1989/90, when it rose from 9.6% to 11.4%.
The risk of tonsillectomy, after dropping markedly from 10.0% to 6.2% between 1981 and
1983, rose strongly in 1989/90, and by 1998/99, at 8.9%, had almost reached the 1981 level.
126 The risk of adenoidectomy followed a similar pattern to that of tonsillectomy, with a sharp decrease between 1981 and 1983 followed by a less pronounced increase and a leveling out by 1998/99. However, at 9.6% the risk of adenoidectomy remained considerably lower than the 1981 level of 11.6%.
As an example of how the risk of ENT surgery differed by age, Table 3.6 shows the estimated risks by single year of age from the1989/90 and 1998/99 lifetables.
Table 3.6 Cumulative risk of NSW children having ENT surgery by single year of age, from 1989/90 and 1998/99 lifetables Age % at risk of surgery
1989/90 (1998/99)
Tonsillectomy Adenoidectomy Myringotomy ENT surgery
By age 1 year 0.0 (0.0) 0.0 (0.0) 0.3 (0.4) 0.3 (0.4)
By age 2 years 0.0 (0.1) 0.2 (0.3) 1.3 (1.8) 1.4 (1.9)
By age 3 years 0.3 (0.7) 0.6 (1.0) 2.3 (3.1) 2.7 (3.7)
By age 4 years 1.1 (1.7) 1.7 (2.3) 3.9 (4.7) 4.8 (6.1)
By age 5 years 2.1 (3.0) 3.2 (3.9) 5.7 (6.4) 7.5 (8.9)
By age 6 years 3.4 (4.2) 4.9 (5.4) 7.6 (8.0) 10.5 (11.6)
By age 7 years 4.5 (5.3) 6.3 (6.6) 9.1 (9.2) 13.0 (13.8)
By age 8 years 5.3 (6.1) 7.3 (7.4) 10.0 (10.1) 14.7 (15.5)
By age 9 years 5.9 (6.7) 7.9 (8.0) 10.4 (10.6) 15.9 (16.6)
By age 10 years 6.4 (7.2) 8.4 (8.5) 10.8 (10.9) 16.7 (17.6)
By age 11 years 6.8 (7.6) 8.7 (8.8) 11.0 (11.2) 17.4 (18.2)
By age 12 years 7.1 (8.0) 9.0 (9.1) 11.1 (11.3) 17.9 (18.8)
By age 13 years 7.4 (8.3) 9.2 (9.3) 11.3 (11.4) 18.4 (19.3)
By age 14 years 7.8 (8.6) 9.3 (9.5) 11.3 (11.5) 18.8 (19.7)
By age 15 years 8.0 (8.9) 9.4 (9.6) 11.4 (11.6) 19.2 (20.2)
127
As can be seen in Table 3.6, cumulative risk of surgery increases steeply until 8 years of age for all types of ENT surgery, and moderately thereafter.
Trends in surgery rates
To better illustrate trends, initial plots of rates shown in Table 3.2 were made (Figure 3.3).
Figure 3.3 Rate of ENT surgery per 100,000 NSW children aged 0-14 years,
1981 - 1998/99
1600
1400
1200
1000
800
Rate/100,000 600
400
200
0 1980 1985 1990 1995 2000 Year
ENT surgery T onsillectomy Adenoidectomy Myringotomy
In Figure 3.3 it can be seen that, over the whole period 1981 to 1999, ignoring at this point the fluctuations, there has been an overall upward trend in rates of ENT surgery, especially in rates of myringotomy. Poisson regression analysis was used to verify and quantify these overall trends over the whole study period for each procedure. In this stage of the analysis, a 128 single expression of overall change in practice between the beginning and end of the study period was required for each procedure, in contrast with later analysis into the effect of guidelines on rates, when the study period was subdivided. This single expression of change was needed for interpretation of the data owing to its complexity, in that comparisons were required for each of the three procedures, and to allow for later comparison between six age and gender subgroups for each of the procedures.
In these Poisson regression analyses, exponential functions were used so that results could be expressed in terms of percentage changes per annum. Estimates of increase per annum for each procedure resulting from these analyses are shown in Table 3.7.
Table 3.7 Estimated trends in rates of ENT procedures, 1981 - 1998/99 Parameter Tonsillectomy Adenoidectomy Myringotomy ENT procedure
Base Year Base Year Base Year Base Year
Estimate -5.256 0.00178 -5.077 0.00068 -5.167 0.01878 -4.523 0.01087
Standard 0.00792 0.00063 0.00729 0.00058 0.00724 0.00056 0.00536 0.000422 Error P <0.0001 <0.01 <0.0001 n.s. <0.0001 <0.0001 <0.0001 <0.0001
%p.a. change +0.1784 n.s. +1.8957 +1.0929
It can be seen in Table 3.7 that rates of total ENT surgery increased between 1981 and
1998/99 by 1.1% per annum (99% C.I. 1.0-1.2), equating to 21% over the whole period. Most of this increase was attributable to the increase in myringotomy rates. Myringotomy rates increased by 1.9% p.a. (1.7-2.0), or 39% over the whole period. Tonsillectomy rates
129 increased by 0.2% p.a. (0.02-0.3), or 3.2% over the whole period. Adenoidectomy rates did not change significantly.
Trends in age- and gender-specific procedure rates
Rates of each type of ENT surgery varied widely by age and gender. Age- and gender- specific tonsillectomy rates observed over the study period are shown in Table 3.8.
Table 3.8 Observed age- and gender-specific tonsillectomy rates per 100,000 NSW children, 1981 – 1998/99 Year 0-4 years 5-9 years 10-14 years
Male Female Male Female Male Female
1981 605 444 977 1041 245 478
1983 343 275 683 684 158 322
1986 388 319 795 842 218 454
1988/89 422 330 804 807 193 462
1989/90 494 364 883 882 245 434
1990/91 513 354 845 867 260 450
1991/92 543 361 807 907 260 496
1992/93 583 441 792 900 279 469
1993/94 559 406 807 833 237 460
1994/95 595 429 731 720 220 367
1995/96 606 447 741 767 235 377
1996/97 554 410 665 676 182 333
1997/98 636 431 758 726 233 390
1998/99 708 483 817 838 249 436
130 These age- and gender-specific tonsillectomy rates were entered into Poisson regression models to obtain estimates of trends over the whole study period. Results for each age and gender group are shown in Table 3.9.
Table 3.9 Estimated age- and gender-specific trends in rate of tonsillectomy: 1981 - 1998/99 Age of child Gender of % per annum rate 99% Confidence % increase or child increase or Interval decrease, decrease 1981-1998/99 0-4 yrs Male +2.5 +2.1,+2.9 +54.5
Female +1.8 +1.4,+2.3 +37.8
5-9 yrs Male -0.8 -1.1,-0.5 -13.3
Female -1.0 -1.3,-0.7 -16.2
10-14 yrs Male +0.7 +0.1,+1.3 +12.4
Female -0.5 -0.9,-0.1 -8.5
In Table 3.9 it is seen that the total rate increase over the whole study period was 54.5% for males and 37.8% for females aged 0-4 years, while among males and females aged 5-9 years there were total decreases of 13.3% and 16.2% respectively. In the age group 10-14 years, male rates increased by 12.4% and female rates decreased by 8.5% over the study period.
Estimated rates for each ISC year were evaluated from the above regression results and plotted against the observed values from Table 3.8 (Figure 3.4).
131 Figure 3.4 Estimated and observed age-specific tonsillectomy rates/100,000 children,
1981-1998/99
1200
1000
800
600
400
Rate/100,000 males 200
0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
1200
1000
800
600
400
200 Rate/100,000 females Rate/100,000
0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
Figure 3.4 shows that children aged 5-9 years had the highest rates of tonsillectomy throughout the study period, with similar rates for males and females. The male 0-4 year rate at the beginning of the period was far lower than the 5-9 year rate, but by the end of the period was almost as high. Males aged 10-14 had the lowest rates throughout. The female 5-9 and
10-14 year rates remained reasonably similar and level during the study period. 132
These tonsillectomy estimates showed that males outnumbered females in the youngest age group, with the opposite occurring in the oldest group, and the male/female ratio being reasonably balanced among those aged 5-9 years.
Adenoidectomy age- and gender-specific rates observed over the study period are shown in
Table 3.10.
Table 3.10 Observed age- and gender-specific adenoidectomy rates per 100,000 NSW children, 1981 – 1998/99 Year 0-4 years 5-9 years 10-14 years
Male Female Male Female Male Female
1981 863 582 1289 1208 174 280
1983 582 450 958 861 131 183
1986 593 434 977 924 165 211
1988/89 679 484 1052 962 170 253
1989/90 748 535 1123 1029 191 238
1990/91 766 567 1080 996 205 277
1991/92 820 525 1047 995 217 304
1992/93 861 642 1021 1020 243 273
1993/94 839 575 1020 982 193 262
1994/95 862 569 898 795 177 224
1995/96 835 568 888 799 162 199
1996/97 852 602 864 782 141 206
1997/98 892 589 929 799 200 238
1998/99 944 613 930 862 191 280
133 From Table 3.10, age- and gender-specific adenoidectomy rates were entered into Poisson regression models to obtain estimates of trends over the whole study period. Results for each age and gender group are shown in Table 3.11.
Table 3.11 Estimated age- and gender-specific trends in rate of adenoidectomy: 1981 to 1998/99 Age of child Gender of % per annum rate 99% Confidence % increase or child increase or Interval decrease, decrease 1981-1998/99 0-4 yrs Male +1.8 +1.5,+2.2 +37.8
Female +1.3 +0.9,+1.7 +25.9
5-9 yrs Male -1.4 -1.7,-1.2 -22.3
Female -1.6 -1.9,-1.3 -24.3
10-14 yrs Male +0.9 +0.2,+1.6 +16.5
Female Not significant
Over the whole study period, adenoidectomy rates increased most in the youngest age group, by 37.8% for males and 25.9% for females, while rates among males and females aged 5-9 years decreased by 22.3% and 24.3%. In the oldest age group, female rates did not change and male rates increased by 16.5%.
Estimated rates were calculated from the Poisson results and plotted against observed rates from Table 3.10 in Figure 3.5.
134 Figure 3.5 Estimated and observed age-specific adenoidectomy rates/100,000
children, 1981-1998/99
1400 1200 1000
800 600
400
Rate/100,000 males Rate/100,000 200
0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
1400 1200 1000
800 600
400
Rate/100,000 females Rate/100,000 200
0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
Figure 3.5 shows that children aged 5-9 years had the highest rates of adenoidectomy in all the study years. However, the rate for males aged 0-4 years rose to the same level as that of those aged 5-9 years by the end of the study period. The female 0-4 rate also increased, but did not reach the 5-9 year level. Male rates were approximately 50% higher than female rates in the 0-4 age group and 10% higher in the 5-9 age group, but approximately 20% lower
135 among those aged 10-14 years. Higher male rates of adenoidectomy among children aged under 10 years have also been reported in Finland (Mattila).
Age- and gender-specific myringotomy rates observed over the study period are shown in
Table 3.12.
Table 3.12 Observed age- and gender-specific myringotomy rates per 100,000 NSW children, 1981–1998/99 Year 0-4 years 5-9 years 10-14 years
Male Female Male Female Male Female
1981 742 425 952 720 157 101
1983 933 675 1178 836 128 115
1986 901 589 927 716 125 110
1988/89 1125 764 1058 848 136 112
1989/90 1374 919 1172 921 143 109
1990/91 1301 935 1031 883 164 126
1991/92 1336 867 1061 790 152 101
1992/93 1491 997 1122 921 142 131
1993/94 1461 930 1019 847 133 113
1994/95 1557 974 946 712 96 92
1995/96 1419 918 908 686 98 85
1996/97 1594 1089 979 743 125 95
1997/98 1505 921 1035 752 132 110
1998/99 1567 999 1009 765 137 133
136 From Table 3.12, age- and gender-specific adenoidectomy rates were entered into Poisson regression models to obtain estimates of trends over the whole study period. Results for each age and gender group are shown in Table 3.13.
Table 3.13 Estimated age- and gender-specific trends in rate of myringotomy between 1981 and 1998/99 Age of child Gender of % per annum rate 99% Confidence % increase or child increase or Interval decrease, decrease 1981-1998/99 0-4 yrs Male +4.0 +3.7,+4.3 +98.9
Female +3.7 +3.4,+4.1 +90.1
5-9 yrs Male -0.3 -0.6,-0.1 -5.6
Female Not significant
10-14 yrs Male -1.0 -1.7,-0.2 -15.5
Female Not significant
Myringotomy rates increased most in the youngest age group, doubling over the study period for males and increasing by 90.1% for females. By contrast, rates of myringotomy for males decreased, by 5.6% for those aged 5-9 years and by 15.5% among those aged 10-14 years, and did not change for females in these age groups. The male rate exceeded the female in all age groups, especially 0-4 years, where the final male/female ratio was 1.55.
Estimated rates were calculated from the above Poisson results and plotted against observed rates from Table 3.12 in Figure 3.6.
137 Figure 3.6 Estimated and observed age-specific myringotomy rates/100,000 children,
1981-1998/99
1800 1600 1400 1200 1000 800 600 400 Rate/100,000 males Rate/100,000 200 0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
1200
1000
800
600
400
200 Rate/100,000 females Rate/100,000
0 1980 1985 1990 1995 2000 Year
0-4yrs observed 0-4yrs estimated 5-9yrs observed 5-9yrs estimated 10-14yrs observed 10-14yrs estimated
In Figure 3.6 it is seen that myringotomy rates were higher for males than for females in both younger age groups and similarly low for those aged 10-14years. For both males and females aged 5-9 years rates were initially higher than the 0-4 year rates until between 1985 and 1990, when rates for the youngest age group rose to become the highest in the final study years.
138 Changes in age profiles, 1988/89-1998/99
The above changes led to changing age profiles for each procedure. Figure 3.7 shows the change in profile for tonsillectomy within the decade 1988/89 to 1998/99.
Figure 3.7 Age profile for tonsillectomy, 1988/89 and 1998/99
1400
1200
1000
800 88/89
600 98/99 Rate/100,000 400
200
0 1 2 3 4 5 6 7 8 9 101112131415 Age
Figure 3.7 demonstrates a shift in the peak age for tonsillectomy from 6 years to 5 over the decade. While some increase in rates occurred among children aged 6 years, most increase has been among children younger than 6 years. By contrast in Finland in 2001 the peak age for tonsillectomy was 5 – 9 years (Mattila).
Figure 3.8 illustrates the change in age profile for children having adenoidectomy.
139 Figure 3.8 Age profile for adenoidectomy, 1988/89 and 1998/99
1800
1600
1400
1200
1000 88/89 800 98/99
Rate/100,000 600
400
200
0 123456789101112131415 Age
Figure 3.8 shows the effect of tonsillectomy rate changes noted in the previous section. As well as shifting towards a younger age, there have been marked increases in rates, which become greater with decreasing age.
The myringotomy age profiles appear in Figure 3.9.
Figure 3.9 Age profile for myringotomy, 1988/89 and 1998/99
2000 1800 1600 1400 1200 88/89 1000 98/99 800 Rate/100,000 600 400 200 0 123456789101112131415 Age
140 Figure 3.9 clearly demonstrates that the increase in rates over the decade 1988/89 to 1998/99 has occurred in the under 5 years age group.
Changes in prevalence of surgery among children aged 0-4 years
Since the increases in surgical activity over the study period were found to be limited almost exclusively to children in the youngest age group, it was decided to scrutinise this age group more closely. For this analysis only tonsillectomy and myringotomy were examined, since adenoidectomy patterns were reasonably similar to those of tonsillectomy.
As described in the Methods, the availability of successive years of data between 1988/89 and
1998/99 enabled the actual surgical experience of successive cohorts of children to be followed in each year for ages 0 to 4 years. Tonsillectomy rates for these children are presented in Table 3.14.
Table 3.14 Rate of tonsillectomy per 100,000 children for seven successive cohorts born 1988/89 to 1994/95 by age at time of surgery Age Year of tonsillectomy 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99
0 2.3 1.2 5.7 4.5 9.0 7.9 4.6
1 41 86 82 77 83 93 96
2 296 338 415 377 447 400 400
3 792 862 853 826 892 866 946
4 1237 1118 1196 1236 1042 1138 1286
The tonsillectomy rates experienced by each cohort in successive years can be followed by examining the diagonals in Table 3.14. For example, the cohort born in 1988/89 produced the
141 age 0 rates in 1988/89, the age 1 rates in 1989/90, age 2 rates in 1990/91, age 3 rates in
1991/92 and age 4 rates in 1992/93 (2.3, 40.5, 288.5, 765.2 and 1197.4/100,000 respectively).
Hence Table 3.14 reveals the tonsillectomy experience of seven successive birth cohorts, children born in 1988/89 through to 1994/95, at each year of age.
Similarly the myringotomy experience of successive cohorts of children is shown in Table
3.15.
Table 3.15 Rate of myringotomy per 100,000 children for seven successive cohorts born 1988/89 to 1994/95 by age at time of surgery Age Year of Myringotomy 88/89 89/90 90/91 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99
0 195 250 287 317 318 338 343
1 1090 1164 1203 1258 1234 1458 1419
2 1015 1095 1235 1154 1195 1162 1372
3 1401 1568 1526 1496 1400 1535 1506
4 1903 1776 1864 1558 1755 1643 1716
By using the diagonals as cohort-specific experience, accumulation of the Table 3.14 and
Table 3.15 rates represents the prevalences of tonsillectomy and myringotomy for each cohort at each year of age under five years.
In Table 3.16 the age-specific prevalences of the cohort of children born in 1988/89 are compared with the prevalences of the cohort born 6 years later, in 1994/95.
142 Table 3.16 Age-specific prevalence of surgery per 100,000 children: cohort born during 1988/89 compared with cohort born during 1994/95 Age at Tonsillectomy Myringotomy
surgery 1988/89 1994/95 % 1988/89 1994/95 %
cohort cohort increase cohort cohort increase
< 2 years 43 100 132.2 1284 1763 37.2
< 3 years 339 500 47.6 2299 3135 36.3
< 4 years 1131 1446 27.8 3700 4641 25.4
< 5 years 2368 2732 15.4 5603 6357 13.4
Table 3.16 shows that the prevalence of tonsillectomy more than doubled among children aged under 2 years in the later-born cohort, and increased by 47.6% among children under 3 years. The picture was similar but more moderate for myringotomy, with prevalence among children aged under 2 and 3 years increasing by as much as 37.2% and 36.3% respectively in the later born cohort.
Procedure combinations over time
The three ENT procedures can be performed singly or in four possible combinations. The percentage performed in each way in each of the study years is compared in Table 3.17.
143 Table 3.17 Percentage of ENT procedures performed singly or in combination, 1981 - 1998/99 Year Single procedure Combined procedure Total Ton Ade Myr Ton+ Myr+ Myr+ Ton+ Ade Ade Ton Ade+ Myr 1981 9.1 6.7 25.5 38.8 11.9 0.8 7.2 100.0 1983 8.8 6.4 40.5 23.9 13.7 0.6 6.1 100.0 1986 13.3 7.1 34.5 27.0 11.1 0.7 6.3 100.0 88/89 10.8 7.4 37.3 24.2 12.6 0.8 6.9 100.0 89/90 10.3 6.7 39.8 23.7 11.7 0.8 7.2 100.0 90/91 10.0 7.0 38.1 24.6 12.1 1.0 7.2 100.0 91/92 10.7 7.5 37.8 25.5 11.2 0.8 6.6 100.0 92/93 10.4 6.9 39.2 23.8 12.0 1.0 6.8 100.0 93/94 10.3 7.3 39.2 24.2 11.4 0.9 6.7 100.0 94/95 9.7 6.4 41.4 23.9 10.7 0.9 7.0 100.0 95/96 11.7 6.4 39.6 24.6 10.2 0.8 6.7 100.0 96/97 9.1 6.4 43.4 21.6 12.1 0.8 6.7 100.0 97/98 10.3 6.3 40.2 23.9 11.3 0.9 7.0 100.0 98/99 11.8 6.5 39.1 24.0 10.4 1.4 6.8 100.0 Ton: Tonsillectomy, Ade: Adenoidectomy, Myr: Myringotomy
There was very little change in the mix of surgery over the study period, with two exceptions
(Table 3.17). Myringotomy performed alone increased from 25.5% of ENT procedures in
1981 to 39.1% in 1998/99. However the percentage of myringotomy combined with another
ENT procedure remained reasonably stable, being 19.9% in 1981 and 18.6% in 1998/99.
Adenotonsillectomy declined during this period from 39% to 24%. Both these changes occurred in the early years of the study period. The percentage of tonsillectomies performed singly also increased from 9.1% to 11.8%, again with the shift occurring in the early years.
These combination percentages and their changes over time are illustrated in Figure 3.10.
144 Figure 3.10 ENT surgery combinations, 1981-1998/99
100%
90%
80% Tonsillectomy,Adenoidectomy & Myringotomy 70% Myringotomy&Tonsillectomy 60%
50% Myringotomy&Adenoidectomy
40% Tonsillectomy&Adenoidectomy 30%
20% Myringotomy
10% Adenoidectomy 0% Tonsillectomy 1981 1983 1986 1988/89 1989/90 1990/91 1991/92 1992/93 1993/94 1994/95 1995/96 1996/97 1997/98 1998/99
Figure 3.10 shows how, by the end of the study period, myringotomy had replaced tonsillectomy with adenoidectomy as the dominant paediatric ENT procedure. Tonsillectomy and adenoidectomy remain procedures more often performed together than in isolation.
Geographical variation
As explained in the Methods (Chapter 2), owing to changed administrative boundaries, it was only possible to examine five of the study years for geographical variation. The years for which Area populations relating to the earlier boundaries were available were 1988/89 –
1992/93. Although calculated for the other four years, only the 1992/93 standardized separation ratios, that is, each Area's rate, standardised by age and gender and expressed as a ratio relative to the State average, are shown in Table 3.18. Of the 5 years for which these ratios were calculable 1992/93 was selected as being the most recent year.
145 Table 3.18 Indirectly Standardised Ratios by Area/District Health Service for tonsillectomy, adenoidectomy and myringotomy, 1992/93 Type of Area/ District Health Tonsillectomy Adenoidectomy Myringotomy geographical Service area Inner Southern Sydney 76.1(66.8,85.3) ↓ 81.9(7.30,90.7) ↓ 84.2(76.0,92.4) ↓ metropolitan Eastern Sydney 71.4(57.1,85.7) ↓ 96.5(81.3,111.7) 123.3(107.7,139.0) ↑ Central Sydney 80.3(66.3,94.3) ↓ 97.6(83.5,111.8) 125.2(110.5,139.8) ↑ Western Sydney 78.7(70.6,86.7) ↓ 83.6(75.9,91.3) ↓ 85.0(77.9,92.1) ↓ Northern Sydney 98.1(88.6,107.6) 120.6(110.8,130.3) ↑ 139.0(129.4,148.7) ↑ Outer Wentworth 93.8(81.8,105.7) 104.5(93.0,116.1) 108.7(97.9,119.6) metropolitan Sth Western Sydney 120.5(111.5,129.6) ↑ 87.6(80.5,94.7) ↓ 85.6(79.1,92.0) ↓ Central Coast 128.9(112.5,145.3) ↑ 124.6(109.8,139.3) ↑ 140.3(126.0,154.6) ↑ Hunter 86.6(77.2,96.1) ↓ 87.7(79.0,96.5) ↓ 100.6(92.0,109.2) Illawarra 108.6(95.4,121.9) 159.6(144.8,174.4) ↑ 138.9(126.2,151.6) ↑ Rural Central West 157.9(137.0,178.7) ↑ 135.7(117.9,153.5) ↑ 137.8(121.2,154.3) ↑ South Eastern 78.0(62.9,93.0) ↓ 60.0(47.9,72.1) ↓ 51.2(40.9,61.4) ↓ North Coast 136.7(123.6,149.8) ↑ 106.6(95.9,117.3) 76.4(68.0,84.7) ↓ North Eastern 88.2(75.3,101.1) 88.9(77.0,100.8) 88.8(77.9,99.8) ↓ Orana Far West 87.3(70.7,103.9) 79.5(65.0,94.0) ↓ 85.4(71.6,99.1) ↓ South Western 104.3(90.5,118.1) 104.2(91.5,116.9) 54.5(46.0,62.9) ↓ ↓ indicates rate significantly (p<0.01) lower than State average (100) ↑ indicates rate significantly (p<0.01) higher than State average (100)
Table 3.18 shows that surgery rates varied significantly by Area of residence. Rates of
tonsillectomy were relatively low in the inner metropolitan areas, and tended to be high in the
outer metropolitan and rural areas. Rates of adenoidectomy were mostly low in the inner
metropolitan areas, with the exception of Northern Sydney and mixed in the other areas.
Rates of myringotomy were mostly high in the inner metropolitan areas, mixed in the outer
metropolitan and mostly low in the country areas. To determine whether Areas maintained the
same relative positions for each type of ENT procedure, inter-correlations were performed
using the above indirectly standardised ratios. There was a significant positive correlation
between adenoidectomy and tonsillectomy (r2 = 0.61, p = 0.01) and between adenoidectomy 146 and myringotomy (r2 = 0.74, p = 0.001), but no relationship between tonsillectomy and myringotomy.
To determine whether the variability found between Areas represented systematic rather than chance differences, variability indices were computed for each of the five years for which standardised ratios had been calculated, 1988/89 - 1992/93. For these indices 95% confidence intervals were calculated (Table 3.19).
Table 3.19 Inter-area variability indices for tonsillectomy, adenoidectomy and myringotomy, 1988/89 – 1992/93 Year Variability index (95% confidence interval)
Tonsillectomy Adenoidectomy Myringotomy
1988/89 0.28 (0.12, 0.44) 0.40 (0.08, 0.73) 0.39 (0.09, 0.69) 1989/90 0.22 (0.12, 0.32) 0.30 (0.12, 0.47) 0.26 (0.12, 0.39) 1990/91 0.25 (0.12, 0.38) 0.27 (0.12, 0.42) 0.23 (0.12, 0.34) 1991/92 0.22 (0.12, 0.32) 0.23 (0.12, 0.35) 0.25 (0.12, 0.38) 1992/93 0.24 (0.12, 0.35) 0.23 (0.12, 0.34) 0.29 (0.12, 0.45)
For all years and each of the procedures, the variability indices were significantly above zero.
This confirmed the presence of persistent systematic variation in rates of surgery between the
Areas in each of these years.
Management of acute otitis media by general practitioners, 1990/91 and 1998/99
A special analysis of the BEACH data, which contain the results of statewide surveys of general practitioners, was undertaken to determine whether the increase found in the rate of myringotomy could be explained by an increase in the incidence of otitis media, a frequent precursor of myringotomy. The rate of management of acute otitis media by NSW general
147 practitioners among children aged 0-14 years in 1990/91 was compared with the rate in
1998/99.
This analysis revealed that acute otitis media was managed at 9.4% (95% C.I. 8.7%-10.1%) of children’s consultations with a NSW family physician in 1990/91 compared with 8.7%
(95% C.I. 7.9%-9.5%) in 1998/99, which did not represent a statistically significant change.
However, later published data show that the management rate declined in 2000/01 to 7.7%
(7.1% - 8.3%), significantly lower than the 1990/91 rate51.
Far from supporting a hypothesis of increased otitis media among children as a cause of the increased rates of myringotomy found in this study, this analysis has demonstrated the opposite, that otitis media was managed by general practitioners less frequently during the period covered by the study. It could be speculated that this might reflect a change toward earlier onward referral of such cases to specialists, which might result in a lower surgical decision threshold.
148 DISCUSSION
Burden of paediatric ENT surgery on the health system
Examination of the epidemiology of paediatric ENT surgery in NSW has shown its burden on the health system to be considerable. Such surgery accounts for one in every eight hospital admissions of children aged under 15 years, and almost one in five of children aged 5-9 years.
Not considered in this section is the further burden of associated non-hospital services, such as surgeons’ fees, which are partly borne by Medicare, and medical tests and examinations surrounding the surgical episode.
Epidemiology of ENT surgery
This study has presented new information on the epidemiology of ENT surgery among NSW children over almost two decades. In the final study year, 1998/99, the rate of all ENT surgery for children aged under 15 years was 13.4/1000. Their rate of tonsillectomy was
5.9/1000, of adenoidectomy 6.4/1000 and of myringotomy 7.7/1000.
Trends in ENT surgery
ENT surgery rates increased by 21% over the whole study period. While most of this increase was attributable to myringotomy, which increased by as much as 39% over the whole period, tonsillectomy rates also increased by 3.2%. The rate of adenoidectomy did not change significantly. An increased proportion of myringotomy and tonsillectomy was performed as the sole ENT procedure, resulting in a changed profile for adjuvant ENT surgery.
Adenotonsillectomy in particular declined proportionally over the study period.
149 The risk of a NSW child having some form of ENT surgery by the age of 15 years increased from 17.9% in 1981 to 20.2% in 1998/99. For myringotomy, the risk increased from 8.1% to
11.6% during this period. While the risk of tonsillectomy did decrease slightly between 1981 and 1998/99 (from 10.0% to 8.9%), this risk remains far higher than the 1983 level of 6.2%.
International comparison
Owing to the paucity of comparable rates, it is difficult to describe exactly where NSW stands relative to other countries, although in general terms NSW has much in common with these countries.
Prior to the period of the current study, from 1961 until about 1983, tonsillectomy rates declined greatly in all countries including NSW (Table 3.3). The U.S. decline continued through 1991204. Available data from Scotland shows that tonsillectomy rates per 1,000 children aged 0-15 years declined from 7.8 in 1975 to 4.0 in 1982167. Similarly, in NSW the all-age rate decreased by 66% between 1978 and 1983 (Table 3.3). Results of the current study show that, for NSW children aged 0-14 years, rates declined from 6.3/1,000 in 1981 to
4.0/1,000 in 1983. After 1983 an increase occurred, both in NSW and Scotland, with reasonably similar rates between 1981 and 1990. By 1990 the rate for NSW children aged 0-
14 years had risen to 5.5/1,000, and for Scottish children aged 0-15 years to 6.0/1,000 (Table
3.3). Rates in 1990/91 in Canada were higher than both NSW and Scotland19 169 (Figure 3.1).
After 1990 there was no published data for Scotland, while in NSW, tonsillectomy rates continued to rise after 1990, reaching 5.9/1,000 children aged 0-14 years in 1998/99, the final year of the current study. In the absence of data for this later period, it is not known whether the level in NSW remained comparable with international trends.
150 Myringotomy trends were very different. The myringotomy procedure began to become popular after 1967160, and rates increased greatly in all countries including NSW until the mid-1980s. Myringotomy rates for children aged under 10 years in East Anglia and Oxford1,
5.0/1,000 in 1975, reached a peak of 13.2/1,000 in 1986 (Table 3.4), after which they declined to 6.8/1,000 in 1998. By contrast, NSW rates continued to climb after 1986, reaching a peak of 11.0/1,000 in 1989. However, for the period 1986 to 1992, rate levels in
East Anglia/Oxford and NSW were approximately similar. A marked difference occurred after 1993, when the English rates declined to 6.8/1,000 while the NSW rates remained on approximately the same level, reaching 10.6/1,000 in 1998/99 (Figure 3.2). It may be that grommet insertion trends in NSW lag about 5 years behind these English regions. However, there is as yet no evidence of a decrease in myringotomy rate occurring in NSW.
No decline in any of the ENT procedures has yet occurred in NSW, with rates of ENT surgery being even higher at the end of the study period than at the start.
Predisposing factors for surgery
In common with many other studies, the current study has found age of child and area of residence to influence the likelihood of having ENT surgery. In the current study children residing in metropolitan areas were far more likely to have surgery than rural children were.
One explanation for this could be a relative scarcity of hospital facilities and surgeons, or it could be due to remoteness and an attitude of self-sufficiency among rural residents. The greater likelihood of surgery among young children is discussed in the following paragraphs.
151 More surgery among young males
Throughout the study period, rates of tonsillectomy and adenoidectomy were found consistently to be higher among male than female children under 5 years, with rates of myringotomy also being higher for males aged 5-9. Similar results have been reported elsewhere for myringotomy168, and males have also been found to have a higher prevalence of
OME61. However, the reason for this gender imbalance is unknown.
Increased surgery for the very young
The most surprising finding of the current study has been that the increase in rates found overall, among those aged 0-14, has been brought about by hugely increased rates among the youngest age group, with rates in the intermediate and oldest age groups either remaining unchanged or declining. The risk of surgery among the very young has become even greater.
The opportunity afforded by the comprehensiveness of the Inpatient Statistics Collection enabled closer examination of this phenomenon. By following successive cohorts of children and comparing their surgical experience over their first five years of life, this study has revealed that the prevalence of children born in 1994/95 who had had tonsillectomy by age 2 was more than double that of children born six years earlier (Table 3.16: 100/100,000 compared with 43/100,000), and their prevalence by age 5 years 15% greater (2,732/100,000 compared with 2,368/100,000). Similarly the increase in prevalence of children who had had myringotomy by the age of 2 years was 37% higher than that of the cohort born six years earlier (1,763/100,000 compared with 1,284/100,000), and their prevalence by age 5 years
13% higher (6,357/100,000 compared with 5,603/100,000).
152 Possible explanations for increasing rates among young children
These findings imply that either there has been a radical shift in belief regarding the suitability of very young children for these procedures, new indications for surgery have emerged, or the morbidity of the child population has changed, necessitating earlier surgical treatment.
If beliefs have changed, then reasons for this change have not been articulated. A belief in the improved safety of surgery may be contributing to the increased surgery rates among very young children. One Italian study reported on the safety of tonsillectomy and adenoidectomy for 166 children less than 3 years of age229. However, surgery still has risks for young children: 7 of 29 children aged 3 years or under who had undergone tonsillectomy and adenoidectomy required inpatient admission due to complications, mainly respiratory211.
Recommendations regarding age were made in neither Australian ENT guideline13 14.
Increased surgery may have resulted from the emergence of new indications. Indications for myringotomy might have changed to reflect increased concern over the effect of temporary loss of hearing due to OME on language development in young children, together with an increased availability of paediatric audiometry. However the extent of this effect is disputed
137. In a study of children under 2 years of age with OME, Paradise et al failed to find any developmental differences at the age of 3 years between children randomly assigned to have tubes inserted promptly and those who waited for nine months before surgery. The 1993 myringotomy guidelines did note that "in babies and young children hearing loss may have an effect on socialisation and speech development", but advise taking this suspected factor, the assessment of which is subjective, into consideration only when OME has persisted for over three months, not as a primary indication. In the current study, among children who had
153 myringotomy with or without adenoidectomy, hearing related diagnoses declined over the period. Hence hearing concerns as an indication for surgery do not explain the increases in myringotomy rates found in this study
.
With regard to tonsillectomy, there is evidence that an increasingly important indication 201 is heightened concern over the effects of sleep apnoea on young children. Obstructive sleep apnoea has increased as an indication for tonsillectomy from 0% in 1978 to 19% in 1986201 and 72% in 1996211 225, and detection of this condition through oximetry and polysomnography has become increasingly available. Adenotonsillectomy is an effective treatment for this condition, which affects approx 2% of preschool children178 311 and can result in neurocognitive deficits and failure to thrive186 187 195 222 227 312. Although the 1982 tonsillectomy guideline cited airway obstruction, signalled by "loud snoring during sleep with intermittent obstructive apnoeic episodes" as a major indication, the changes noted in the current study in the age of children undergoing such surgery have occurred at a considerable distance in time from the publication of these guidelines. In addition the current findings show that, although a diagnosis of apnoea increased during the period 1988/89 to 1998/99, among children who had tonsillectomy and/or adenoidectomy, the percentage with this diagnosis remained negligible (2%) and could not account for the increased rates of surgery found.
Several arguments exist to support the possibility that the increases found might be due to increased morbidity among the child population in the current era. Joki-Erkkila63 found that the percentage of children under 10 years diagnosed with AOM in Finland grew from 14% in
1978/79 to 21% in 1994/95, while surgical treatment doubled from 6% to 12% over the period. However in NSW, the general practitioner survey data showed that the rate of
154 management of otitis media among children aged under 15 years who attended a family physician declined between 1990/91 and 2000/0151. This finding is in contrast with increases found in Belgium over two decades60 and also in the U.S., where the proportion of children who had experienced otitis media (carer-reported) in the previous year was higher in the 1994 than the 1988 national survey 62. Acute otitis media is said to be developing at an earlier age and the proportion of children having multiple episodes before age 1 year has increased over the past decade118. Allergy is an increasing problem worldwide78 including Australia, where the prevalence of sinusitis doubled among the general population between 1989/90 and 1995 and hay fever increased from 10% to 13%313. Asthma has also doubled among NSW schoolchildren between 1982 and 1992314. Allergy is associated with otitis media with effusion76, with chronic rhinosinusitus74 and with tonsillar hypertrophy315. Antimicrobial resistance is widespread and increasing and associated with a decreased rate of eradication of pathogens from middle ear fluid.40
Young age and day-care attendance have been shown to be risk factors for development of resistance 316 and for receiving tympanostomy tubes53 81. Daycare attendance has been shown to increase the risk of otitis media, possibly by exposing the young child to pathogenic microbes not encountered at home64 65 79 82 317. In Australia, the proportion of children under
12 years attending childcare increased from 39% in 1984 to 48% in 1996 and has stayed relatively constant at this rate85. The greatest increase in formal childcare attendance has been among those aged 3-4 years where rates increased from 10% in 1984 to 66% in 1999 and from 8% to 22% for those aged 0-2318. Hence this may have contributed to increased rates of morbidity in these young children.
155 Parental work is the main reason for the increased use of formal childcare among young children85. Therefore it is possible that there is additional pressure on parents and doctors to attempt to promptly resolve illness among children, and this may have led to a reduced decision-threshold for procedural intervention. In the U.K. no such association between amount of childcare for young children and rates of ENT surgery appears to hold. Despite the number of childcare places in England for children under 8 years having increased substantially319, glue ear surgery rates in children under 10 in two regions of the UK fell reasonably consistently between 1981 and 1997/98320.
156 CONCLUSION
The current study has found that rates of ENT surgery in NSW increased over two decades and such surgery has been newly directed towards the very young. The procedure combination analysis (Table 3.17) has shown that myringotomy has displaced adenotonsillectomy as the most frequently performed ENT procedure. However, this displacement is proportional – the amount of tonsillectomy and adenoidectomy did not decrease in absolute terms. Instead, rates have increased overall, and attempts have been made to understand the reason for these trends. These ENT procedures are well established, and it might be reasonable to suppose that the number of such procedures performed would reflect changes in population numbers, while rates would remain stable.
There is little evidence to suggest that this upward trend has been due to changes in the underlying morbidity of the paediatric population. Technical change and medical advances underlie much fluctuation18. The lack of any effective alternative treatment and improved safety of surgery underlay the almost routine removal of tonsils and adenoids in the 1940s and
1950s. Changes in morbidity were deemed unlikely to explain why the rate of myringotomy in the U.K. in the 1970s rose to the extent of its being described as an epidemic160. In recent decades there has been heightened concern over the effects of sleep apnoea177 186 187 221 222 312 and temporary hearing loss25 321 on child development and this may have played a role.
What influences the surgical decision? The guideline movement focusses almost exclusively on the physician as being the arbiter of this decision. Guidelines are aimed at physicians in an attempt to change their practices277. In the case of elective surgery, guidelines attempt to curb
157 the unnecessary performance of surgery by promoting standardised responses to specified symptoms.
During the period covered by the current study, two sets of guidelines aimed at clarifying
ENT surgical criteria were disseminated in NSW. The following chapter examines the effect of guideline dissemination on the rate of ENT surgery, and also examines hospital-recorded diagnoses for evidence of compliance with guideline surgical indications.
158 CHAPTER 4 EFFECT OF GUIDELINES ON RATES OF ENT SURGERY
This chapter examines the effect of guidelines on rates of ENT surgery. It also examines whether guideline-recommended indications for surgery are reflected in diagnoses recorded on the hospital record.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions background & methods & methods & methods & methods & aims Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 7 Chapter 4 ENT Economic Effect of cohort impact: guidelines on utilisation: Results & rates Results & discussion discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
159 INTRODUCTION
As described earlier, in 1993 the NSW Health Department disseminated consensus guidelines for the management of paediatric middle ear disease13, with the stated aim of providing a framework for the development of management guidelines by individual primary care practitioners. The implicit expectation of these guidelines was that reduction of uncertainty would result in a reduced rate of surgery. However, despite the effort and resources employed in producing and disseminating these myringotomy guidelines in 1993, their effect has not been comprehensively examined. One survey of their impact on clinicians and the extent of the clinicians’ agreement with guideline recommendations was carried out297. However, their effect on rates has not been examined, nor has there been any analysis of compliance with specific guideline recommendations.
In this chapter, the effect of these guidelines on rates of myringotomy is examined. The effect of the other relevant set of guidelines, the tonsillectomy and adenoidectomy guidelines which were disseminated in 1982, is also examined, taking into consideration that the range of years of the current study only contained one prior year, 1981.
The following specific effects of these guidelines were determined:
• the impact of guideline dissemination on rates of surgery
• the impact of guideline recommendations on recorded indications for surgery
160 METHODS
Study design
The study design is a comparison of rates before and after two interventions.
Data source
The source of data for this comparison was the rates of ENT surgery previously obtained for each ISC year, and further examination of hospital records in two ISC datasets.
Statistical analysis
Rate trends pre- and post-surgery
Surgery rates for all children aged 0-14 for each year of surgery were analysed using Poisson regression models. Three periods representing before and after introduction of the 1982 and the 1993 guidelines were contrasted with regard to their level of rates and trends during the period. As there was only one year of data prior to the 1982 tonsillectomy and adenoidectomy guidelines, the first period comprised only the ISC years 1981 to 1983. The periods were
• 1981-1983: to represent the period from the year before the 1982 tonsillectomy and
adenoidectomy guideline publication to the year after (As explained in Methods, Chapter
3, 1982 data were omitted from the study as unreliable)
• 1986 - 1992/93: pre-1993 myringotomy guidelines (also post-1982 tonsillectomy and
adenoidectomy guidelines)
• 1993/94 - 1998/99: post-1993 myringotomy guidelines
Poisson regression models were again selected for the current analysis for their capacity to summarise relative risk in the presence of possibly interacting covariates306. Records entered
161 into each model consisted of counts of cases, relevant YEAR (1 to 18.5), and guideline period, with (log) population as offset. Three dummy variables were created with value 0 or 1 to represent each of the guideline periods, 1981-1983 (PERIOD1), 1986-1992/93 (PERIOD2),
1993/94-1998/99 (PERIOD3).
For each of the three ENT procedures, a model was set up as
COUNT = YEAR + PERIOD2 + PERIOD3 + PERIOD2*YEAR +PERIOD3*YEAR
(with PERIOD1 as the base period – however, the choice of base did not affect results).
Results were interpreted in a similar manner to the previous models. The YEAR estimate represented the annual rate change in the base period. The PERIOD estimates represented the change in level at the start of the comparative period, and the PERIOD*YEAR interactions represented differences from the base period in terms of annual rate change. Estimates are derived in Poisson regression from the exponent of the coefficient and interpreted as percentages. In these models statistical significance was set at p<0.01.
Diagnosis
Both sets of guidelines made specific recommendations regarding indications for surgery.
Some indications equate roughly to certain diagnoses. To determine whether indications for surgery had changed following guideline dissemination, the percentage of records with such diagnoses were compared for selected years. Frequency distributions of the first and second recorded diagnoses were obtained and compared for two ISC years, 1988/89 and 1998/99.
These years represented two periods, the first after the tonsillectomy and adenoidectomy guidelines and before the myringotomy guidelines, and the second after both sets of guidelines.
162 The most prevalent and relevant ICD9-CM codes were summarized and proportions of cases with the following diagnoses determined.
Diagnosis ICD9-CM code
OME 38110-3829
Chronic disease of tonsils and adenoids 4740-4749
Acute otitis media 38100-38102
Acute respiratory infections 460-4659
Hearing loss 3890-3899
Apnoea 78050-78609, exc. 7847, 7848
Crosstabulations were made of the first diagnosis, classified into one of the above groups with all other codes forming a separate group, by type (all 7 possible combinations) of surgery.
These 7 surgery combinations were then grouped in a clinically meaningful way – the first group comprised myringotomy, adenoidectomy or myringotomy with adenoidectomy, the second group was tonsillectomy with or without adenoidectomy, and the third group tonsillectomy with myringotomy or tonsillectomy with myringotomy and adenoidectomy. For each group, the proportion with each diagnostic group was determined and examined for changes between 1988/89 and 1998/99, using the z-test for differences in proportion305. This process was repeated for the relatively few cases which had a second diagnosis recorded, and examined in the same way to see whether the conclusions drawn from the first diagnosis analysis were valid.
163 RESULTS
Effect of guidelines on rates of surgery
Changes in rates of surgery before and after dissemination of the two sets of guidelines were estimated using Poisson regression analysis. The results of these analyses yielded estimated trends during each of three periods, 1981 – 1983 (the year before to the year after 1982 tonsillectomy and adenoidectomy guidelines, data for 1982 being unavailable as explained in
Methods), 1986 – 1992/93 (pre-1993 myringotomy guidelines) and 1993/94 – 1998/99 (post-
1993 myringotomy guidelines).
Table 4.1 Results of Poisson regressions by type of ENT procedure
Procedure Parameter Estimate S.E. estimate |T| value p Tonsillectomy Base rate -4.835 0.0181 267.13 <0.0001 Annual change -0.2247 0.008915 25.20 <0.0001 Adjustment to -0.6399 0.02997 21.35 <0.0001 base rate: 1986-1992/93 Adjustment to base rate: -0.576 0.04981 11.56 <0.0001 1993/94-1998/99 Adjustment to annual +0.2505 0.009224 6.56 <0.0001 change: 1986-1992/93 Adjustment to annual +0.2355 0.009368 3.26 <0.001 change: 1993/94-1998/99 Adenoidectomy Base rate -4.737 0.01671 283.48 <0.0001 Annual change -0.1774 0.008059 22.01 <0.0001 Adjustment to base rate: -0.6752 0.02789 24.20 <0.0001 1986-1992/93 Adjustment to base rate: -0.3783 0.04639 8.15 <0.0001 1993/94-1998/99 Adjustment to annual +0.2124 0.008355 6.56 <0.0001 change: 1986-1992/93 Adjustment to annual +0.1782 0.008495 3.26 <0.001 change: 1993/94-1998/99 Myringotomy Base rate -5.364 0.01935 277.21 <0.0001 Annual change +0.09679 0.008337 11.61 <0.0001 Adjustment to base rate: -0.08546 0.02877 2.97 <0.01 1986-1992/93 Adjustment to base rate: +0.3636 0.04357 8.34 <0.0001 1993/94-1998/99 Adjustment to annual -0.04511 0.008594 6.56 <0.0001 change: 1986-1992/93 Adjustment to annual -0.09022 0.008681 3.26 <0.001 change: 1993/94-1998/99
164 In Table 4.1 it can be seen that for each type of surgery the starting levels and trends of the pre- and post-guideline periods differed significantly in. These estimates were applied to the relevant years and periods and their exponents calculated. Table 4.2 interprets Table 4.1 and expresses results in terms of estimated rate in the first year of each period, percentage change in rate per annum during each period and estimated rate in the last year of the period.
Table 4.2 Estimated trends in rates of ENT surgery pre- and post- tonsillectomy and myringotomy guidelines
Type of ENT Period % change per Total Estimated Estimated surgery annum during estimated rate per rate per period (99% C.I.) % change 100,000 at 100,000 at during start of end of period period period Tonsillectomy 1981-1983 -20.1 (-21.9,-18.3) -36.2 635 405
1986-1992/93 +2.6 (+2.0,+3.2) +18.2 489 578
1993/94-1998/99 +1.1 (+0.3,+1.8) +5.6 516 545
Adenoidectomy 1981-1983 -16.2 (-18.0,-14.5) -29.8 734 515
1986-1992/93 +3.6 (+3.0,+4.1) +25.4 550 690
1993/94-1998/99 +0.1 (-0.6,+0.8) 0.0 600 600
Myringotomy 1981-1983 +10.2 (+7.8,+12.5) +21.3 516 626
1986-92/93 +5.3 (+4.7,+5.9) +39.9 586 820
1993/94-1998/99 +0.7 (+0.0,+1.3) +3.3 736 760
Tonsillectomy and adenoidectomy results of Table 4.2 are examined first. Rates of both were at their highest levels at the start of the first period, 1981-1983. Between these years, during which tonsillectomy and adenoidectomy guidelines had been disseminated, rates of both procedures dropped sharply, by 36.2% and 29.8% p.a. respectively. However, during the next period, 1986-1992/93, both tonsillectomy and adenoidectomy rates started at a higher level than at the end of the previous period and rose by 2.6% and 3.6% p.a., or 18.2% and 25.4%
165 respectively over the whole period. During the next period, 1993/94-1998/99, which followed the publication of myringotomy guidelines, both tonsillectomy and adenoidectomy rates initially dropped to a lower level; however, after this tonsillectomy rates increased again by
1.1% p.a., or 5.6% over the whole period, while adenoidectomy rates remained unchanged.
By 1998/99 rates of both had settled at relatively high levels.
In contrast, myringotomy rates were at their lowest in 1981, and increased during most of the study period, by 10.2% p.a. between 1981 and 1983, and from their 1986 level until the publication of guidelines by 5.3% p.a. Although in the year following publication rates fell and remained at a lower level in the two subsequent years, after this they rose again slowly, resulting in an increase of 3.3% over the entire post-guideline period.
In Figure 4.1 observed procedure rates for each reporting year between 1981 and 1998/99 are compared with the estimated rates obtained from evaluating the Poisson regression results in
Table 4.2.
166 Figure 4.1 Actual and estimated rates of tonsillectomy, adenoidectomy and
myringotomy per 100,000 children, with trends pre- and post-guidelines
900
800
700
600
500
400 Rate/100,000 300
200 1982 1993 T&A Myringotomy 100 guidelines guidelines 0 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 Year
Observed myringotomy Estimated myringotomy Observed tonsillectomy Estimated tonsillectomy Observed adenoidectomy Estimated adenoidectomy
Figure 4.1 shows the estimated trends for each of the three pre- and post-guideline periods examined, and the changes in level between the end of one period and the start of the next. It illustrates the results of Table 4.2 as well as observed rates.
Recorded diagnosis compared with guideline recommendations
In order to determine the extent to which guideline recommendations regarding indications for surgery were reflected in hospital record diagnoses, these diagnoses were examined in two periods, 1988/89 and 1998/99. In this examination, due to differing combinations of surgery having been performed, meaningful groups of these surgery combinations were formed.
Adenoidectomy, myringotomy and myringotomy with adenoidectomy (A/MA/M) were considered to comprise one such group, tonsillectomy and tonsillectomy with adenoidectomy
(TA/T) another, and myringotomy with tonsillectomy and myringotomy with tonsillectomy
167 and adenoidectomy (MT/TAM) a third. For the group A/MA/M, the percentage of cases which had diagnoses selected as being relevant to this procedure group were as follows in
1988/89 and 1998/99 (Table 4.3).
Table 4.3 Selected diagnoses recorded for children who had myringotomy, adenoidectomy or myringotomy and adenoidectomy: 1988/89 compared with 1998/99
Recorded Guideline % of total diagnoses Difference z p diagnosis recommended indication 1988/89 1998/99
OME Yes 79.4 82.4 +3.0 4.84 <0.001
Acute otitis media No 4.4 0.8 -3.6 -14.93 <0.001
Hearing loss Yes 2.5 1.0 -1.5 -7.85 <0.001
Acute respiratory No 0.18 0.05 -0.13 -2.50 <0.05 infections Apnoea Yes (adenoidectomy) 0.14 0.10 -0.04 -0.72 n.s. No (myringotomy) Selected diagnoses as % of total diagnoses 86.6 84.4
Total children in procedure group 8450 9867
Between 1988/89 and 1998/99, the proportion of cases receiving a diagnosis of OME increased proportionally by 3.7%, while diagnoses of acute otitis media and acute respiratory infections, not recommended by guidelines as indicators for myringotomy, dropped proportionally by 82% and 72% respectively. The diagnosis ‘hearing loss’, although comprising a very small percentage in both years, also decreased by 60% proportionally.
There was no change in the tiny amount of myringotomies with a diagnosis of apnoea. The diagnoses selected for examination covered most diagnoses recorded for children in this procedure group.
168 For the group TA/T, the percentage of cases with selected relevant diagnoses in 1988/89 and
1998/99 were as follows (Table 4.4).
Table 4.4 Selected diagnoses recorded for children who had tonsillectomy or tonsillectomy with adenoidectomy: 1988/89 compared with 1998/99 Recorded diagnosis Guideline % of diagnoses Difference z p recommended indication 1988/89 1998/99
Chronic disease of Yes 88.4 93.2 +4.8 8.86 <0.001 tonsils and adenoids Acute respiratory No 8.9 2.0 -6.9 -15.89 <0.001 infections Apnoea Yes 0.44 2.2 +1.8 8.62 <0.001
Selected diagnoses as % of total diagnoses 97.7 97.4
Total children in procedure group 5169 6322
The diagnosis, chronic disease of tonsils and adenoids, increased to 93.2% over the period, a proportional increase of 5.4%, while diagnoses of acute respiratory infections declined proportionally by 78%, both changes being in line with guideline recommendations. The percentage diagnosed with apnoea rose to 2.2%, a five-fold increase: however, the absolute size of this increase was too small to explain the increases found in tonsillectomy rates. The selected diagnoses covered almost all diagnoses recorded for children in this procedure.
For the group MT/TAM, the percentage of cases with selected relevant diagnoses in 1988/89 and 1998/99 were as follows (Table 4.5).
169 Table 4.5 Selected diagnoses recorded for children who had tonsillectomy with myringotomy, or tonsillectomy with myringotomy and adenoidectomy: 1988/89 compared with 1998/99 Recorded diagnosis Guideline % of diagnoses Difference z p recommended indication for 1988/89 1998/99 tonsillectomy OME No 16.8 14.8 -2.0 -1.39 n.s.
Acute otitis media No 1.45 0.07 -1.38 -3.81 <0.001
Hearing loss No 0.28 0.07 -0.21 -1.22 n.s.
Acute respiratory infections No 6.1 1.4 -4.7 -6.04 <0.001
Apnoea Yes 0.4 2.2 +1.8 4.15 <0.001
Chronic disease of tonsils Yes 71.2 79.3 +8.1 4.73 <0.001 and adenoids Selected diagnoses as % of total diagnoses 96.2 97.8
Total children in procedure group 1134 1438
For those children who had a combination of tonsillectomy and myringotomy, with or without adenoidectomy, the diagnoses mostly related to tonsillectomy. Among these, acute respiratory infections declined as a diagnosis, and both apnoea and chronic disease of tonsils and adenoids increased between the two periods, both in line with guideline tonsillectomy indications. Diagnoses related to myringotomy (acute otitis media, OME and hearing loss) all declined over the period, again suggesting that tonsillectomy was the primary and myringotomy the adjunct procedure. These selected diagnoses covered almost all recorded diagnoses for this procedure group.
A second diagnosis was recorded in 13% of 1988/89 cases, and in 28% of 1998/99 cases.
Examination of these secondary diagnoses supported the above findings.
170 DISCUSSION
This analysis has shown that the introduction of guidelines in NSW was associated with a short-term reduction in paediatric ENT surgery rates. Procedure rates decreased in the two to three years immediately following guideline dissemination. In the case of tonsillectomy and adenoidectomy, these decreases may have been following the worldwide trend mentioned previously, rather than resulting from publication of the 1982 tonsillectomy and adenoidectomy guidelines.
In the case of myringotomy, rates decreased in each of the three years following dissemination of guidelines regarding this procedure. Surprisingly, tonsillectomy and adenoidectomy rates also decreased following these guidelines. The myringotomy guidelines may have prompted clinicians to re-evaluate their practice in tonsillectomy and adenoidectomy since rates for these procedures were also published at this time 163.
Wennberg322 found feedback of population-based data on tonsillectomy rates to be associated with significant declines in tonsillectomies in the U.S..
The finding of a short-term impact of guidelines agrees with that of Mason et al323 in the U.K.
In the current study, similar to Black et al320, a long period was examined. However, contrary to the findings of Black et al, none of the decreases were found to be sustained in the longer term. Six years after the introduction of guidelines, NSW myringotomy rates had almost reached the peak rate found in the immediate pre-guideline year, while the tonsillectomy rate had increased by 1998/99 to the highest rate in any study year since 1981. A letter regarding the current findings has been published 324 (Appendix 6). The limited impact found in NSW may have been due to both sets of guidelines having been set by government agencies rather
171 than otolaryngologic professional groups, although representatives of such groups were included in their development. Black et al320 attributed the continued decline in the English
ENT rates to many factors, including publication of guidelines, professional concern about rates, introduction of an internal market into the NHS, and media pressure, all of which created an environment conducive to change. This reasoning might also explain why tonsillectomy and adenoidectomy rates fell with the introduction of myringotomy guidelines in NSW.
Hence, as seen in this and other studies, the dissemination of guidelines does appear to encourage fresh interest. However, such restraint is relatively short-lived. As found in NSW, rates can soon rise again310 324.
The failure to find a sustained guideline effect on ENT surgery in NSW indicates the presence of the influence of other factors. It is often argued that guidelines alone are not sufficient to change practice 286 260. Physicians sometimes disagree with, or distrust, recommendations, preferring to rely on their own experience or that of their colleagues.252 277 For example,
Paradise 185 in 1979 described the prevailing medical opinions regarding tonsillectomy and adenoidectomy as being polarised, and Black18 described the rate of surgery for glue ear in
1985 as an epidemic owing its popularity to fashion rather than science.
However, this study has provided evidence pointing to some other possibly enduring effects of guidelines. The analysis of diagnosis in two years a decade apart, 1988/89 and 1998/99, has shown an increase in conditions which the 1993 guidelines sanction as indications for surgery, and a decrease in conditions the guidelines do not recommend. For those children who had
172 myringotomy, adenoidectomy or both procedures, the diagnosis OME increased over the period, while acute otitis media or acute respiratory infections declined. However, the percentage diagnosed as being hearing-related, which should be a major indication for myringotomy, also declined among this group. For children who had tonsillectomy and/or adenoidectomy, the percentage diagnosed with chronic disease of tonsils and adenoids increased, while acute respiratory declined. It does appear that some aspects of better practice advocated by guidelines get adopted.
At least two conditions must be met for surgery to occur. First, there must be a belief that the benefit of surgery will outweigh its considerable cost207. Such a belief may well be held by parents as well as the physicians they consult. Second, symptoms which are indications for surgery must be present. However, precise definition of such symptoms should be unambiguous, or state the quality of evidence supporting their inclusion246. Clinical practice guidelines do not always disclose uncertainty in their recommendations252. Examination of the
NSW guideline criteria for tonsillectomy and adenoidectomy184 or myringotomy13 reveals that some descriptions of symptoms are vague or subject to interpretation. The symptoms themselves - hypertrophy of tonsils or adenoids, tonsillitis, otitis media, symptoms suggestive of sleep apnoea, such as snoring - are very common and widespread among children. For as long as the environment is conducive to restraint, a strict interpretation of such symptoms is probably taken1, whereas, when opinion swings towards an enhanced belief in the benefits of surgery, a broader interpretation may be taken, and this is likely to be a leading cause of the peaks found historically. Hence it does appear that the first condition for surgery, belief in its efficacy, is subject to the current climate of medical opinion. It is towards rationalising this climate of opinion towards the best available evidence that guidelines are addressed.
173 In subsequent chapters the extent of the contribution of child-based factors to the surgical decision is examined.
174 Chapter 5 UTILISATION OF HEALTH SERVICES BY A COHORT OF NSW CHILDREN: INTRODUCTION & METHODS
This chapter presents a detailed rationale for the examination of child-based factors that might contribute to the surgical decision, specifically, the utilisation of health services by individual NSW children. Methods of determining such utilisation in order to make a comparison between children who have ENT surgery and those who do not are presented.
Health services examined include selected privately funded inhospital services as well as those delivered outside the hospital setting.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 11 Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 14 Introduction Research Introduction Introduction Introduction Conclusions background & methods & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline surgery Total cohort Subsequent compliance: rates: utilisation: utilisation: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 13 Chapter 4 Chapter 7 ENT Economic Effect of cohort impact : guidelines on utilisation: Results & rates Results & discussion discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
175 INTRODUCTION
In Chapter 3, rates of ENT surgery among the NSW paediatric population were found to vary over time, by geographical area and between age groups. Such variation in elective surgery rates is commonly attributed to differences in local medical practice183, and guidelines, as well as attempted explanations for such variation, reflect a basic assumption, that the opinion of the physician, the major arbiter of the surgical decision171, is the major factor underlying differences in the performance of surgery. The influence of two sets of guidelines on rates of surgery was examined in the previous chapter.
Other studies have suggested the characteristics of the children who have surgery as a possible factor underlying rate variation 167. Bisset suggested that her finding of higher rates of tonsillectomy among children residing in Scottish regions of low socioeconomic status might be due to poorer health among these children, a result of deprivation and poor nutrition.
If so, findings of rate variation may reflect health status rather than individual practitioner opinion. So, the question raised is, is the health of children who have surgery generally poorer than that of those who do not?
Children do suffer conditions that cause concern, both to parents and their physicians. These conditions require treatment, and surgery is one option. Many symptoms fall into a grey area and are subject to a great deal of discretion207 Identical symptoms, such as OME and recurrent tonsillitis, may be treated with surgical intervention in some cases and in other cases not10 15 209. Assuming that the child is exhibiting symptoms of concern, does the choice of treatment rest entirely on the physician? Are symptomatic children who are treated surgically identical to those treated non-surgically? To answer this question requires the accurate
176 measurement of presenting symptoms. Several studies have addressed this aspect and have focussed on determining whether indications for surgery have been met150 156 185.
In the current study another approach is proposed which aims to address the question whether, prior to their having surgery, these children seek medical advice more often than the children who do not have ENT surgery? If these therapeutic interventions are aimed at correcting the conditions for which medical attention is sought, it would be logical to find evidence of more than the usual amount of consultation prior to the procedure. In the current study, this hypothesis is tested by examining these children’s medical histories and by comparing their patterns of use of health services with those of children who do not have surgery. It is recognized that utilisation of such health services does not necessarily denote illness in the child and might reflect such factors as parental attitudes and behaviour. However, the converse is not true. True illness or the presence of a medical problem would almost certainly result in a health contact of some kind, especially in a country such as Australia, where there is almost unfettered access to medical services. Hence, while use of such services may also be due to other reasons, ill health is reflected in use of medical services. It thus seems logical to examine whether patterns of utilisation of health services by children who have ENT surgery differ in any way from patterns of those who do not have such surgery.
If no difference were to be found, this would confirm that the locus of control of the surgical decision resides mainly with the physician, in that an identical amount of presentations, implying a similar level of illness, has led to differing forms of treatment, surgical and non- surgical. Such a finding would lend weight to the importance of guidelines as an instrument of influencing this control. However, if patterns of utilisation were found to differ, then it would
177 mean that there are factors located within the child, including more serious illness, which influence the surgical decision.
In the following chapters this particular issue is explored, namely, what kind of health services are used by children and with what frequency, and whether children who receive
ENT surgery differ in any way from their peers in their use of such services prior to their surgery. Little is known about the consulting behaviour of children outside the hospital setting. There exists no baseline of health service utilisation for the NSW paediatric population. Hence the first step in this part of the research was to examine such utilisation and establish a baseline.
An opportunity to conduct such an examination was seen in the existence and method of management of Australia's comprehensive medical insurance scheme, Medicare. This scheme is administered by the Health Insurance Commission (HIC), which maintains records regarding claims and payments made under the scheme. While the bulk of funding for this scheme comes from general taxation, all Australian taxpayers are required to make an additional special-purpose Medicare contribution, currently at the rate of 1.5% of gross income, and in return are entitled to claim benefits from the scheme.
These HIC data were considered a valuable and rare source for the examination of individual patterns of health service utilisation and hypothesis testing. In NSW, no other health data collection system covers both inpatient and non-inpatient occasions of service. The ISC data from which the previous results (Tables 2.1-2.19) were obtained are limited to inpatient hospital episodes. Other sources, such as the GP survey (described in Chapter 2 and analysed
178 in Chapter 3) or the Australian Health Survey, which is conducted occasionally by the
Australian Bureau of Statistics, do not contain patient information, which is needed in order to identify children who had surgery. Data from both the GP survey and the Australian Health
Survey, while containing more detailed health information than the HIC records, are based upon samples, and hence are not large enough to test hypotheses on small subgroups of interest. By contrast, the HIC data cover the entire population. They consist of unit records which cover all episodes of non-inpatient care in the population, as well as all privately financed episodes of inpatient care. Type of service or procedure is exactly specified via a unique code; however, reasons for consultations are not coded. Medicare has a unique identification system which enables every episode of care for which a benefit is claimed to be matched for an individual.
The current chapter details the method of selection of a representative cohort of the NSW paediatric population from these Medicare data and method of analysis for the establishment of a baseline of claims for medical services, the first step in this section of the program of research.
179 METHODS
Study design
The design of this study is ex post facto research into the characteristics of a population cohort of children selected on the basis of a specific birth date, with the aim of identifying those children who had had ENT surgery and comparing them with the cohort children who had not had surgery.
Data source
The source of data for this study phase was the Health Insurance Commission (HIC), which manages the Australian Medicare Program. This Program provides access to medical and hospital services for all Australian residents325. Medicare pays benefits for professional services rendered by registered medical practitioners. This includes inpatient services which are privately funded, as well as all non-inpatient consultations, pathology and diagnostic services. The Medicare program does not cover inpatient services provided by public hospitals to non-paying patients, nor non-inpatient services provided by the outpatient and
Accident and Emergency Departments of a public hospital. This means that these services will not appear in HIC records. However, the proportion of non-inpatient services provided by public hospitals is relatively low. Although “GP-type” services can be obtained in the
Accident and Emergency Departments, such services are actively discouraged. The funding of medical services in Australia is arranged so that public hospitals and their services are funded by State governments whereas private physician services are funded by the Commonwealth government through Medicare. Public hospitals are not allowed to make claims on Medicare.
Hence there is a disincentive for public hospitals to provide “GP-type” services. In addition
Accident and Emergency Departments are usually overstretched and waiting times are long, sometimes in excess of 4 hours. While, by contrast, private GP services are readily available,
180 except in remote areas, and most provide some after hours services. This means that attendance at an Accident and Emergency Department is usually for a very acute condition or for an injury where further treatment might be required. The proportion of such services relative to the private system of Medicare must hence be very low. As there is no centralised data collection system for the Accident and Emergency or Outpatients Departments of public hospitals, the exact proportion is unknowable. Such Departments are, in any case, restricted to large public hospitals. Individual hospitals may carry out special purpose surveys to determine the load of “GP-type” services, but such data are not generally available. Medicare also funds the practitioner component of inhospital services rendered to privately insured patients.
The HIC holds a comprehensive data collection of records of all services for which a
Medicare Benefit Scheme (MBS) claim is paid. Each record in the data file represents a claim paid for a medical service rendered to the (uniquely identified) individual making the claim.
Data from the HIC are protected under the Health Insurance Act 1973 (Commonwealth of
Australia), and release of information about individual persons is protected under this Act.
Data are stored chronologically by date of processing the claim.
Selection of subjects
A complete set of medical claims of a cohort of children over a number of years was obtained with the aim of comparing the health service utilisation of children who do not have surgery with that of those who do.
Sample size
The size of the cohort needed for the study was determined in the following way. Since the current administrative procedure in the HIC is to hold data for five calendar years in an
181 immediately accessible location, with the remainder being archived, it was decided that
January births would provide the maximum months of follow-up for any one year, given that there is little seasonal variation in NSW births326. With approximately 80,000 births in NSW each year, the number of children being born in any calendar month was estimated to be about
7000. Virtually all these children would be enrolled for Medicare benefits, if not immediately, at the time of claim for their first medical service.
Whether a cohort consisting of one month’s births would be sufficiently large to test statistical hypotheses was determined in the following way. According to the lifetable analyses in
Chapter 3, the risk of a NSW child having ENT surgery by 8 years of age was 15.5% in
1998/99 (risk at the intermediate age of 8 years was calculated but not reported in Table 2.3).
Hence, among a cohort of 7000 children followed until the age of 8 years, about 1085 would be expected to have ENT surgery as a public or private patient. However, since Medicare only records claims paid for privately funded surgery, and privately funded surgery represents approximately half of total ENT surgery (Chapter 3), only about 500 children would be identifiable in the Medicare dataset. Whether such a size (500) would be adequate for testing hypotheses of equality with the rest of the cohort (population) was determined as follows.
Without having a priori knowledge of the approximate size of means or standard deviations, the proportional method was used to determine adequacy. This method requires only an
estimation of the population proportion. Let x and x1 be the number of claims exceeding a specified amount for the population and surgery (sample) groups respectively, with
population sizes n and n1, and p and p1 their respective excess proportions. According to large sample theory (which may be used where sample size is greater than 200 and p lies between
182 0.025 and 0.975327), the difference between a sample proportion and the population proportion
(E) will be at most
E = z α/2 √p (1 - p)/n
Therefore
2 n = p(1 – p)[ z α/2 / E ]
Supposing p to be 0.15 and the difference between p and p1 (E) to be 0.05, and setting α stringently at 0.01, then n = 338. Hence the expected surgery sample size of 500 would be more than adequate to test possible differences between these children and the remaining
6300 cohort children.
Since HIC policy was to retain only five years of current data before archiving, the initial request needed to be for the most appropriate five years which were determined as follows.
As the youngest children had been found to be the main contributors to the increase in ENT surgery rates, and very few would have had such surgery in their first year of age, the five years, which covered ages one to five inclusive, were of most interest to study. Hence a birth month, January 1990, was selected so that the children born in this month would have reached six years of age by late 1996, when the request was made for five years of data. The children were aged one to five years during these years, 1991-1996.
Cohort description
The information was obtained from the HIC (Appendix 7). The HIC was requested to identify a cohort of children through their unique Medicare number and to provide records of all claims relating to those children. The children were to be de-identified and randomly allocated sequential identifying numbers, which would allow for later matching of records of
183 individuals. The HIC provided a historical record of all claims made over the period initially specified (January 1991 to December 1995) by all children appearing in the Medicare enrolment file as at 20/8/96 (the date on which data was requested), who had a NSW address on that date and had been born during January 1990. Since the MBS system is Australia- wide, claims for medical services received in parts of Australia other than NSW were included in the file supplied by the HIC. Similarly, all claims, regardless of where received in
Australia, as well as children who appeared with a NSW address on 20/8/96 but who might have been born in other Australian States, were included.
All claims for Medicare services received by these children processed between January 1991 and December 1995 were included in the file initially provided. Subsequently, files containing services claimed during 1996 and 1997, the children's seventh and eighth years of age respectively, were provided by the HIC when they became available. A request was also made to the Commonwealth Department of Health and Family Services, who are also custodians of the data, to access the archives to provide data for this cohort to cover January to December 1990, the cohort's first year of age. These data were then included in the data set.
Hence the study design combined retrospective gathering of data from an Australian birth cohort of children who were resident in New South Wales at the time of data collection with two years of prospective data collection.
184 Confidentiality
As previously stated, data from the HIC are protected under the Health Insurance Act 1973
(Commonwealth of Australia) and the release of information about individual persons is protected under this Act. Hence all data provided were matched and de-identified. The HIC performed the matching prior to dispatch, with each child being identified only by a sequential number assigned by the HIC. By this means and within the constraints of confidentiality, it was thus possible to track all medical services received by each child during the specified years.
Record contents
Each HIC record contained a number of items (Appendix 8). The subset of items relevant to this study requested and retained in each record was:
• Unique identifier. The HIC used the actual Medicare number of the child to carry out the
matching of records, but replaced this number with an arbitrary sequential number in the
data provided.
• Gender of child
• Area of residence at time of service. To maintain confidentiality, HIC identified only
broad geographical locations. These locations correspond to 17 Health Areas formerly
used by the NSW Health Department, and consist of nine largely metropolitan areas -
Central Sydney, Northern Sydney, Western Sydney, Wentworth, South Western Sydney,
Central Coast, Hunter, Illawarra and South Eastern Sydney - and eight rural areas -
Northern Rivers, Mid North Coast, New England, Macquarie, Mid Western, Far West,
Greater Murray and Southern. Non-NSW addresses were identified by State. A small
185 number of records affecting 67 children in the years 1990 and 1997 was inadvertently not
allocated to NSW Health Areas, but identified as "NSW".
• Year of service
• Date of service
• MBS item number (old). Every health service eligible for a Medicare benefit has a
unique item number, which identifies the type of service received and the amount of
remuneration applicable. All information regarding eligible services and their item
numbers can be found in the Medicare Benefits Schedule Book, obtainable from the
Commonwealth Government and updated in November each year.
• MBS item number (new). The Medicare Schedule item numbering system changed on 1
December 1991. HIC converted old item numbers to new wherever possible. (Some
items transformed into multiple item numbers and others had significant modifications
made to their description.)
• MBS Category to which item belongs. These are the broadest groups of services used by
Medicare. The MBS Categories are:
1. Professional Attendances 2. Diagnostic Procedures and Investigations 3. Therapeutic Procedures 4. Oral and Maxillofacial Services 5. Diagnostic Imaging Services 6. Pathology Services • MBS Group to which item belongs. These are sub-groups of the Categories mentioned
above. The MBS Groups are:
A1 General Practitioner attendances to which no other item applies A2 Other non-referred attendances to which no other item applies A3 Specialist attendances to which no other item applies A4 Consultant physician attendances to which no other item applies A5 Prolonged attendances to which no other item applies 186 A6 Group therapy A7 Acupuncture A8 Consultant psychiatrist attendances to which no other item applies A9-11 Optometrical & Contact lenses D1 Miscellaneous diagnostic procedures and investigations D2 Nuclear medicine (non-imaging) I1 Ultrasound I2 Computerised tomography (excluding magnetic resonance imaging) I3 Diagnostic radiology I5 Nuclear medicine imaging O1 Consultations O2 Assistance at operation O3 General surgery O4 Plastic and reconstructive O5 Preprosthetic O6 Neurosurgical O7 Ear, nose & throat O8 Temporomandibular joint O9 Treatment of fractures P1 Haematology P2 Chemical P3 Microbiology P4 Immunology P5 Tissue pathology P6 Cytology P7 Cytogenetics P8 Infertility and pregnancy tests P9 Simple basic pathology tests P10 Patient episode initiation P11 Specimen referred T1 Miscellaneous therapeutic procedures T2 Radiation oncology T3 Therapeutic nuclear medicine T4 Obstetrics T5 Assistance in the administration of an anaesthetic T6 Anaesthetics T7 Regional or field nerve blocks T8 Surgical operations T9 Assistance at operations
• Number of services. This data item relates to the rare situation where more than one
identical medical service is performed on the same occasion, and there is no item number
to reflect this.
187 "Old" and "new" item numbers appear on the data record to indicate the modification made by the HIC. Item numbers for some services changed over the period, with a major change occurring in November 1990 when, with the exception of codes covering attendances which remained two-digit, all codes which were previously four-digit were converted to five-digit.
The HIC standardised the items according to the coding current in August 1996. However, some four-digit items transformed into multiple items and others had significant modifications made to their description. All original item descriptions for such items were retained.
Data analysis
The analysis was conducted in two parts. In the first part, total claims made by the entire cohort for health services were examined in order to establish a paediatric service utilisation norm. In this part, services were analysed in aggregate, as if using unmatched data. In the second part, the additional information yielded by matching individual children’s records was utilized to examine individual health service utilisation patterns.
Aggregate analysis
In this part of the analysis, the amount and type of services used by the cohort between birth and 8 years of age was determined. Total frequencies of claims for the eight-year period were obtained for each MBS Category and MBS Group, using the data set as if it consisted of unmatched records. From the frequencies, mean rates of utilisation of services per cohort child were calculated. Averages obtained in this way made no use of the information potentially available on individual children through the availability of matched records.
Rather, the averages gave information about the cohort as a whole.
188 Surgical operations (MBS Group T8) were examined in greater detail. These were analysed by age and gender of child. Male/ female ratios were calculated, adjusting for the difference in the numbers of male and female children. This and subsequent adjustments consisted of multiplying the raw score ratio by the factor, number of females divided by number of males.
The influence of age (in months since birth) and season on the number of claims was investigated using general linear models. The number of claims (CLAIMS) was determined for each of the 96 months covered by the study. Each month of age (AGE) was allocated a sequential code from 1 to 96, with January 1990 coded as 1 and December 1997 as 96.
Season was defined as follows:
• SPRING - September, October, November
• SUMMER - December, January, February
• AUTUMN - March, April, May
• WINTER - June, July, August
Four dummy variables were created to represent these seasons, each having the value 1 or 0.
Two simple linear regression analyses were performed as follows. i. Log(CLAIMS)=AGE ii. Log(CLAIMS)=AGE + SPRING+AUTUMN+WINTER, with summer being defined as the referent season (it made no difference to the relative results which season was chosen to be the referent).
In these models, logarithms were initially used to enable resulting coefficients (estimates) to be expressed in terms of percentage changes per unit (age in months or season), rather than in absolute quantities. The necessity for transformation of the data was then tested, using equation (ii) with untransformed data.
189 Individual patterns of health service utilisation
The preceding aggregate analysis yielded information about average patterns of use by this
NSW cohort. To what extent this average utilisation reflected individual utilisation remained unknown. In this second part of the analysis, such utilisation by individual children was determined. Records were matched and datasets created containing only one record for each child. Each of these records contained the following variables: gender of child, area of residence at date of final claim, and counts of the number of claims made by that child over the eight years in selected claim categories. These categories were:
• total MBS claims
• total general practitioner consultations (MBS Groups A1 and A2)
• total specialist consultations (MBS Groups A3 and A4)
• total diagnostic procedures and investigations and total diagnostic imaging (MBS
Categories 2 and 5)
• total diagnostic radiology (MBS Group I3)
• total pathology services (MBS Category 6)
• total surgical operations (MBS Group T8)
• total optometrical (MBS Groups A9, A10 and A11).
Frequency distributions of these counts (number of claims) made by individual children were obtained. Means of these distributions were identical to those previously calculated in the aggregate analysis. However, since the distributions were found to be positively skewed, these means were considered unsuitable estimates of utilisation by individual children.
Instead, medians, which more accurately reflect utilisation of services by individual children, were calculated for each category of claim. Exact medians, based upon hypothetical
190 continuous distributions, rather than being based upon the observed integer values, were calculated. These exact medians were calculated by linear interpolation as follows328.
Median Frequency = Cumulative frequency / 2
For each value or class (in this case, integers) there are hypothetical class boundaries, for example, for the class (value) 1 the class boundaries would be 0.5 and 1.5. The formula for the exact median value is
(Upper boundary – lower boundary)/ (upper boundary – median value) = (cumulative frequency at upper boundary - cumulative frequency at lower boundary) / (cumulative frequency at upper boundary – median frequency (exact median))
To test whether the relationship found between mean and median held for each gender, medians were calculated by gender for each category of claim. A partial examination of medians at each age was made for two years of age only – under one year and one year.
Medians were not calculated for each of the succeeding years of age because the additional information obtainable did not seem worth the burden of analysis – for each year of age a separate dataset would have had to have been created containing total counts for each child for that year only.
To test the influence of the child's gender on the number of claims made, counts were grouped and cross-tabulations of count by gender with chi-square analysis performed.
Counts of claims were made to determine the influence of area of residence. In these analyses, area of residence was identified as that appearing in the final record of a particular child. As stated earlier, a few records in the years 1990 and 1997 were inadvertently not allocated to
191 NSW Health Areas, but identified only as "NSW". There were 67 children thus affected, and these children were omitted from these analyses. Children resident outside NSW at the time of their final recorded claim (148 children) were also excluded, leaving a total of 6024 children included in the area of residence analyses.
These analyses were performed as follows. The number of claims made by each child was compared with the NSW exact median number of claims. Dummy variables were created recording the outcome of this comparison, with 1 denoting that the child's number of claims was greater than the median and 0 denoting that it was less. This was done for each of the claim categories. (Because the NSW medians were exact while the counts being compared were integers, the proportion of NSW children actually falling above these exact medians differed from 50% in most claim categories. For instance, for claims in the relatively infrequent category of surgical operations, the exact median for NSW was calculated as 0.3, so that only 36.6% of children had claims above this median.) For each claim category, logistic regressions were performed to test whether the proportion of children residing in a particular area who had claims above the median was the same as the proportion of all NSW children. Records for each individual child were used in these logistic regressions, with each record containing the dummy variable denoting above or below the median and variables denoting Area of residence. These Areas were set up as independent dummy variables, with
1 representing residence in a particular area, and 0 non-residence. The estimated risk odds ratio (ROR) was defined as the probability that the proportion of children with greater than the NSW median number of claims in an Area was no different from the proportion for the whole of NSW. A conservative level of significance was set at p<0.01 because large numbers (there were over 200 children in most Areas) can result in oversensitivity to small
192 differences, and also because, a significance level set at p<0.05 implies a 1 in 20 chance of a
Type 1 error, and hence, there being 16 Areas, one Area could be wrongly designated as significantly different. In these logistic regressions, the Area with the closest proportion to that of NSW was selected as the substitute for NSW; that is, it was selected to be the default
Area against which the other Areas were compared. Details of these default Areas are noted in the Tables, which present the outcomes of the logistic regressions, together with totals for each Area, their proportions above the NSW median and the proportion above the median for
NSW as a whole, so that it can be seen how closely the proportion in the default Area approximates this proportion.
To illustrate these logistic regression equations, denote Areas as Area1, Area2, Area3, ......
Area16. The form of the logistic function is
F(z) = 1 / (1 + e-z)
Models were set up for each category of claim with z being estimated by
Z = α + β1 Area1 + β2 Area2 + β3 Area3 + β4 Area4 ...... + β16 Area16 with the default Area omitted from the equation in each case to provide the contrast with
NSW. In these models z represents the odds ratio, while the outcome of evaluating the expression 1 / (1 + e-z) represents the proportion above the median.
Advantages of the data
1. The HIC data, on which the health service utilisation section of this study is based, are
a unique source. Their coverage is as complete as any fallible human system can make
it, relying as it does upon financial incentives. Doctors who bulk-bill, that is, receive
85% of the recommended fee directly from Medicare, are unlikely to omit a patient’s
193 details and forgo their fee. Similarly patients who themselves pay their physician will
make every effort to claim a partial refund, thus ensuring that their occasion of service
is recorded in the HIC collection.
2. The ability to track a patient over years of claims through their Medicare number
makes these data unique and valuable. Very seldom can large cohorts be tracked over
a number of years. The data’s coverage of every type of medical service provided
outside the hospital setting is unique.
3. The data also cover some parts of inhospital services and it is this link that has been
exploited in the current study.
Limitations of the data
Interpretation and analysis using these Medical Benefit Scheme (MBS) data was limited by the following factors.
Possible selection bias
1. The cohort may not reflect the health service utilisation of all children born during
January 1990 and resident in NSW at the time of data request. Some NSW residents,
particularly overseas-born persons without permanent residency, are ineligible for
Medicare benefits. Further, a child's appearance in the cohort was dependent upon
the carer making at least one claim for benefit between birth and December 1995, and
thus appearing on the Medicare file at the time of the data request.
2. Some children might have been born overseas but resident in NSW on 20/8/96. As it
was impossible to identify such children, their earlier health service utilisation would
be undetermined, leading to further understatement. Similarly, it was impossible to
determine the extent of attrition by death or departure from Australia.
194 Possible measurement bias
1. Health service utilisation by the cohort during the study period may be under-reported.
One known source of under-reporting would be those services provided by the public
hospital sector to public patients, which are not funded under the Medicare scheme. Of
particular relevance to this study is the known omission of surgery provided to public
patients.
2. Another possible source of under-reporting is the ineligibility of some non-inpatient
services for MBS benefits. As described previously, while Medicare covers the
services of all private medical practitioners, some non-inpatient services for which no
Medicare claim is made such as those provided by Accident and Emergency or
Outpatient Departments of public hospitals do not appear in the data. Hence some
services, particularly trauma-related services, would be under-reported in these data.
3. Another source of under-reporting may be that the data do not include all health
services claimable under the MBS. Services provided might not have been claimed
for, due to oversight or some other circumstance, and hence would not appear in the
data file.
4. Yet more under-reporting could arise if cheques, representing a refund to the recipient,
were inadvertently never presented. A record is raised by the MBS only upon
presentation for payment of a Medicare cheque by the recipient.
5. Diagnosis is not recorded. The presence of some services in the record may not
indicate the presence of a medical condition. Particularly in a cohort of this age
group, this would be the case, for instance, where services were provided for the
purpose of immunisation.
195 6. Some services, such as immunisation, are also provided in Australia by local
government authorities and State health departments directly. Such services would
not appear in these data, which include only services provided by an MBS-accredited
medical practitioner.
7. Residence of a particular area was attributed to the area of residence at the time of
final claim appearing in the data for a particular child, although some children may not
have resided in the same Health Area or in NSW for the whole of the eight years
studied. This means that, while the records of these children would be complete with
regard to services received, since the Medicare system is Australia-wide, not all
services might have been received in the attributed Area.
196 Chapter 6 UTILISATION OF HEALTH SERVICES BY A COHORT OF NSW CHILDREN: RESULTS & DISCUSSION
This chapter establishes a baseline for health service utilisation by NSW children to enable later comparison between children who did or did not have ENT surgery. This baseline covers privately funded inhospital services as well as health services delivered outside the hospital setting. Patterns of utilisation of such services by a cohort of NSW children are followed from birth to eight years of age.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Introduction Chapter 14 Research Introduction Introduction Introduction Conclusions background & methods & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 13 Chapter 4 Chapter 7 ENT Economic Effect of cohort impact: guidelines on utilisation: Results & rates Results & discussion discussion Chapter 8 Comparison: ENT with total cohort: Results & discussion
197 RESULTS
TOTAL CLAIMS FOR HEALTH SERVICES
Total MBS claims
Over the eight years, 1990 to 1997, 372,815 MBS claims were paid by the HIC on behalf of the cohort of 6239 children, 3194 boys and 3045 girls.
Total claims by age of child
The number of claims was greatest in the first year of age (19% of total claims). Figure 5.1 shows the distribution of claims by age of child.
Figure 6.1 Total MBS claims over 8 years by age at time of claim
80000
70000
60000
50000
40000
Claims 30000
20000
10000
0 <1yr 1yr 2yrs 3yrs 4yrs 5yrs 6yrs 7yrs Age
From these totals the average number of claims per child by year of age (which corresponds to year of claim) was calculated (Table 6.1).
198 Table 6.1 Average number of claims per child by age
Year of Age of child Total claims Average claims claim per child 1990 Under one year 71,419 11.4 1991 One year 58,883 9.4 1992 Two years 48,089 7.7 1993 Three years 47,076 7.6 1994 Four years 43,197 6.9 1995 Five years 40,460 6.5 1996 Six years 33,353 5.4 1997 Seven years 30,338 4.9 1990-1997 Birth to under 8 years 372,815 59.8
The average number of claims for children aged under one year was higher than in subsequent years of age. However, this number would presumably include the recommended two-, four- and six-month immunisations (where undertaken by a Medicare-enrolled practitioner).
Likewise, the one-year average could include the immunisation recommended for twelve months of age.
Month of Claim
Figure 6.2 shows the distribution of claims by calendar month and by month of age over the eight year period, from January 1990 (month 1) to December 1997 (month 96).
199 Figure 6.2 Number of MBS claims per month, January 1990 - December 1997, in a cohort of children born in NSW in January 1990
9000 8000 7000 6000 5000 4000 Claims 3000 2000 1000 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 Month
In Figure 6.2 it can be seen that claims declined over time (equivalent to age of child). The
Figure also gives the impression of marked seasonality. Regression analysis confirmed these visual impressions, quantifying the age-related decline in number of claims per month and the seasonal effect (Table 6.2).
Table 6.2 Total (log) claims by age of child and season of year Variable Parameter estimate Standard error p
Intercept 8.41908 0.05344 <0.0001
Age (month) -0.00968 0.00074 <0.0001
Spring 0.24302 0.05768 <0.0001
Autumn 0.31388 0.05757 <0.0001
Winter 0.44837 0.05758 <0.0001
Adj R2=0.7079
200 Table 6.2 shows a highly significant monthly decline in the number of claims per month of age, as well as seasonal changes in claim levels. These regression results are evaluated as follows:
Number of claims in month i = exponent [8.41908 – 0.00968 x i + (0(if summer) or
0.24302(if spring) + 0.31388(if autumn) + 0.44837(if winter)]
Using this method, estimated claims for each month of age were evaluated and plotted against observed claims (Figure 6.3).
Figure 6.3 Observed claims per month compared with regression estimates by age
9000
8000 7000
6000
5000 4000 Claims 3000
2000 1000
0 1 5 9 131721252933374145495357616569737781858993 Age (months)
Observed Estimated
It can be seen that, with the exception of the first 3 months of age, the regression model provided a very good fit of the data, once seasonality was included. Logarithmic transformation of the data was used to enable the trend to be expressed as a rate. On average over the eight-year period, the number of claims decreased at a rate of 1% per month, or 11% p.a. (p<0.0001). Compared with the number of claims during the summer months
201 (December, January, February), claims during spring (September, October, November) were on average 27.5% higher (p<0.0001), claims during autumn (March, April, May) were 36.9% higher (p<0.0001) and claims during winter (June, July, August) were 56.6% higher
(p<0.0001).
An identical regression analysis was performed using untransformed rather than transformed counts to test whether the log transformation was necessary. The results of this analysis are shown in Table 6.3.
Table 6.3 Total claims by age of child and season of year Variable Parameter estimate Standard error p
Intercept 4962.764 206.8998 <0.0001
Age (month) -37.2937 2.8529 <0.0001
Spring 567.0521 223.2961 <0.0128
Autumn 935.2479 222.8583 <0.0001
Winter 1415.5875 222.9131 <0.0001
Adj R2=0.6887
It can be seen that very little improvement in the model was gained through transformation of the counts (an improvement in R2 of only 0.0192). These results are evaluated as follows:
Number of claims in month i =4962.764 – 37.2937x i + (0(if summer) or 567.0521(if spring) or 935.2479(if autumn) or 1415.5875(if winter)
Figure 6.4 shows these evaluated results compared with observed claims for this untransformed model.
202
Figure 6.4 Observed and estimated (non-transformed) claims per month
9000
8000
7000
6000
5000
4000 Claims
3000
2000
1000
0 1 5 9 131721252933374145495357616569737781858993 Age (months)
Observed Estimated
Figure 6.4 shows that the untransformed estimates are very similar to the observed counts
(except again for the high values in the first three months which cause the trend to appear curvilinear). Hence in subsequent analyses logarithmic transformation of the data will be not be undertaken as absolute estimates make their meaning more easily interpretable.
Number and type of claims made by the cohort from birth to 8 years of age
The total number of items claimed in each MBS Category by the cohort between birth and 8 years is shown in Table 6.4.
203 Table 6.4 Total claims by MBS Category, 1990-1997 MBS Category Total claims Number % 1 Attendances 322,482 86.5 2 Investigations 4,181 1.1 3 Procedures 6,550 1.8 4 Oral Maxillofacial 9 0.0 5 Imaging 8,528 2.3 6 Pathology 31,065 8.3 All categories 372,815 100.0
Most of the claims were for professional attendances, followed by pathology services.
Table 6.5 shows the total number of claims made over the 8 years in each MBS Group.
204 Table 6.5 Total claims by MBS Group, 1990-1997
MBS Service Total claims Group Number % A1 General practitioner attendances to which no other item applies 189426 50.8 A2 Other non-referred attendances to which no other item applies 98921 26.5 A3 Specialist attendances to which no other item applies 11903 3.2 A4 Consultant physician attendances to which no other item applies 18339 4.9 A5 Prolonged attendances to which no other item applies 32 0.0 A6 Group therapy 213 0.1 A7 Acupuncture 223 0.1 A8 Consultant psychiatrist attendances to which no other item applies 76 0.0 A10, A11 Optometrical, contact lenses 3349 0.9 D1 Miscellaneous diagnostic procedures and investigations 4174 1.1 D2 Nuclear medicine (non-imaging) 7 0.0 I1 Ultrasound 1272 0.3 I2 Computerised tomography (excluding magnetic resonance imaging) 154 0.0 I3 Diagnostic radiology 6921 1.9 I4 Nuclear medicine imaging 181 0.0 O1 Oral & maxillofacial consultations 5 0.0 O3 General oral & maxillofacial surgery 2 0.0 O4 Plastic & reconstructive oral & maxillofacial operations 2 0.0 P1 Haematology 4429 1.2 P2 Chemical 5281 1.4 P3 Microbiology 12765 3.4 P4 Immunology 732 0.2 P5 Tissue pathology 137 0.0 P6 Cytology 43 0.0 P7 Cytogenetics 83 0.0 P8 Infertility and pregnancy tests 10 0.0 P9 Simple basic pathology tests 171 0.0 P10 Patient episode initiation 7335 2.0 P11 Specimen referred 79 0.0 T1 Miscellaneous therapeutic procedures 98 0.0 T2 Radiation oncology 1 0.0 T5 Assistance in the administration of an anaesthetic 1 0.0 T6 Anaesthetics 2322 0.6 T7 Regional or field nerve blocks 60 0.0 T8 Surgical operations 4025 1.1 T9 Assistance at operations 43 0.0 All MBS 372815 100.0 Groups
Among the MBS Groups, most (51%) claims were for MBS Group A1, vocationally registered general practitioner attendances, followed by MBS Group A2, non-vocationally registered practitioner attendances (26%). In the following analyses, the sum of Groups A1 and A2 was considered to represent total general practitioner attendances. Their sum was
288,347 (77% of the total), an average of 46.2 claims per child over the eight years.
205
There were 30,242 claims for specialist consultations (MBS Groups A3 and A4), 8.1% of total claims, representing 4.8 claims per child on average over the eight years.
Diagnostic procedures and investigations and diagnostic imaging (MBS Groups D1, D2, I1,
I2, I3 and I4, MBS Categories 2 and 5) together accounted for 12,709 claims, 3.4% of the total, averaging 2.0 per child over 8 years. Diagnostic radiology (MBS Group I3) was the greatest contributor to this group (6921 claims), yielding an average of 1.1 claims per child over the eight years.
The pathology groups (MBS Groups P1-P11, MBS Category 6) accounted for 8.3% (31065) of total claims, an average of 5.0 claims per child over the eight years.
There were 3349 optometrical claims (MBS Groups A9, A10 & A11), 0.9% of total, an average of 0.6 claims per child over the eight years.
Total claims for surgical operations (MBS Group T8) were 4025, 1.1% of total claims, or 0.6 claims per child over the eight years.
Number and type of claims by gender of child
To determine whether the number and type of claims for health services differed by gender of the child, a cross-tabulation of total claims was performed. Table 6.6 illustrates gender differences for the most frequent categories of claim.
206 Table 6.6 Total claims by gender of child
Claim category Number of Average Number of Average Male/ claims by claims per claims by claims per female ratio males male females female GP services 152,621 47.78 135,726 44.57 1.07 Specialist services 17,379 5.44 12,863 4.22 1.29 X-rays 3,794 1.19 3,127 1.03 1.16 Pathology 15,863 4.97 15,202 4.99 0.99 Optometry 1,752 0.55 1,597 0.52 1.05 Surgical operations 2,716 0.85 1,309 0.43 1.98 All claims 199,383 62.42 173,432 56.96 1.10
Overall, more claims were made on behalf of boys (mean 62.42, SD 43.49) than girls (mean
57.0, SD 40.6; z=5.103, p<0.0001). Since the skewness of the distribution reflected in the large standard deviations made the z-test questionable, claims were grouped and cross- tabulated by gender. Chi-square confirmed the gender differential (chi-square=38.262, d.f.=17, p=0.002). Males made more claims than females in all claim categories but pathology; that is, the male/female ratio exceeded 1.00.
Claims for surgical operations
In order to determine the importance of ENT surgery relative to all Medicare-claimable surgery, a special analysis of surgical operations was undertaken. The leading types of claims for surgical operations were classified under six major headings, with a number of miscellaneous items.
Table 6.7 shows the number and percentage for each of these main types of surgical operation.
207 Table 6.7 Type of surgical operation, 1990-1997 Type of operation Number % Wound repair 1108 27.5 All ear, nose and throat surgery* 900 22.4 Circumcision/neonatal/hernia 591 14.7 Fracture/dislocation/haemotoma 384 9.5 Burns 121 3.0 Foreign body removal 334 8.3 Other 587 14.6 Total surgical operations 4025 100.0 * Not restricted to tonsillectomy, adenoidectomy and myringotomy
It can be seen in Table 6.7 that most (48.3%) surgery among these children was trauma- related, followed by all types of surgery involving the ear, nose and throat (22%), and circumcision, hernia and other neonatal conditions. Circumcision was the major contributor to the latter group, with 468 claims (11.6% of total surgical operations).
Again, boys had the most surgical operations (Table 6.8).
Table 6.8 Number of surgical operations by gender of child, 1990-1997 Type of surgery Male Female M/F ratio Wound repair 740 368 1.92 Ear, nose and throat surgery 582 318 1.74 Circumcision/hernia/neonatal surgery 565 26 20.72 Fracture/dislocation/haemotoma 227 157 1.38 Burns 91 30 2.89 Foreign body removal 204 130 1.50 Other 307 280 1.05 Total surgical operations 2716 1309 1.98 (Total rate: operations per child) (0.85) (0.43)
208 These differences between the male and female rate of surgical operations were highly significant (p<0.001) in each category except ‘Other’. The male rate remained higher even when the circumcisions, of which there were 468, were excluded.
In Table 6.9 type of surgery is shown by each year of age.
Table 6.9 Number of surgical operations by age of child
Type of surgery <1yr 1year 2yrs 3yrs 4yrs 5yrs 6yrs 7yrs Wound repair 9 184 166 168 175 132 158 116
Ear, nose and throat 39 99 106 169 136 129 111 111 surgery Circumcision/ 418 53 38 27 19 17 14 5 neonatal/hernia Fracture/dislocation 12 21 57 38 46 66 67 77 /haematoma Burns 10 26 34 10 11 15 6 9
Foreign body 5 23 44 66 54 40 56 46 removal Other 101 93 56 61 49 50 85 92
Total surgical 594 499 501 539 490 449 497 456 operations
While the total number of surgical operations remained fairly stable between birth and seven years of age, the types of operations performed differed markedly by age (chi- square=2037.45, d.f.=42, p<0.0001). Among this cohort of children, operations requiring correction of fractures, dislocations and haematomas increased with each year of age, while surgery for wounds peaked between 2 and 4 years of age. Burns were most prevalent between 2 and 3 years of age, while rates of foreign body removal were similar for all ages over 2 years. As expected, most circumcisions, hernia repairs and other neonatal-related conditions took place in the first year. However, there were 28 circumcisions and 13 hernia repairs in the second year, 17 and 15 respectively in the third year, 9 and 13 in the fourth, 7 and 11 in the fifth, 6 and 10 in the sixth, 7 and 5 in the seventh, and 2 and 3 in the eighth year.
209
INDIVIDUAL PATTERNS OF HEALTH SERVICE UTILISATION
Total claims per child
Individual children of the cohort varied greatly in their amount of health service utilisation.
Figure 6.5 shows the distribution of claims per child over the eight years.
Figure 6.5 Total claims per child, 1990-1997
900 800 700 600 500 400 300 No. of children 200 100 0
9 9 9 9 -29 -69 -8 69 09 99 0-9 0 -12 1 2 -22 -26 -3 20 0- 0- 40-49 60 8 00-109 40-149 40-249 80-289 1 120 1 16 180-18920 220 2 260 2 300 No. of claims
In Figure 6.5 it can be seen that the distribution of claims was positively skewed. Attempts were made to normalize the data through transformation of claims. However, these attempts were unsuccessful. Figure 6.6 shows the results of the logarithmic and square root transformations.
210 Figure 6.6 Transformed claims per child, 1990-1997
120
100
80
60
40
Number of children Number 20
0 0123456 Log base e (claims)
120
100
80
60
40
Number of children Number 20
0 051015 Square root of claims
The resulting distributions, as seen in Figure 6.6, were not an improvement on the untransformed data shown in Figure 6.5, which were positively skewed. This was due to the disproportionate influence of a relatively few children with a high number of claims. This resulted in the average number of claims per child quoted in Table 6.1, 59.8, being considerably higher than the median of this distribution, which was 50.5 claims over 8 years.
This pattern persisted in the first two years of age (which were the only two single years analysed in this way).
211 Mean Median Median vs mean
Age < 1 year 12.7* 10.4 17.6% lower
1 year 10.3* 8.2 19.6% lower
* Means differ from those in Table 6.1 owing to Ns in age <1 year and age 1 year datasets being respectively 5628 and 5732 (rather than 6239 for total dataset), because only children with at least 1 claim in these years would have been included. In the full dataset (N=6239) these children would have been included, with 0 claims in years 1 and 2.
General practitioner consultations
The number of general practitioner consultations (Groups A1 and A2) made by individual children over the eight years followed a similar pattern (Figure 6.7).
Figure 6.7 Number of GP consultations per child, 1990-1997
1200
1000
800
600
400 Number of children 200
0
-9 9 9 9 9 0 -49 -69 8 89 60 80- 200+ 20-29 40 00-10 0-12 0-1 1 12 140-149 160-16 18 No. of GP consultations
Again, the distribution was skewed, resulting in a lower median per child of 40.0 GP consultations over 8 years than the average (46.2).
Median and mean claims for GP services by gender and by the first 2 years of age, with median to mean ratios, were:
212 Mean Median Median vs mean
Gender Male 47.8 41.5 13.1% lower
Female 44.6 38.6 13.5% lower
Age < 1 year 9.0 7.9 12.8% lower
1 year 8.7 7.3 16.3% lower
Specialist consultations
Figure 6.8 shows the number of specialist consultations (MBS Groups A3 and A4) per child over the eight-year period.
Figure 6.8 Number of specialist consultations per child, 1990-1997
2000 1800 1600 1400 1200 1000 800 600 Number ofchildren 400 200 0 None 1 to 2 3 to 4 5 to 6 7 to 9 to 11 to 14 to 17 to 21 to 25 to 35+ 8 10 13 16 20 24 34 No.of specialist consultations
Most (71.7%) children had consulted a specialist at least once during the eight-year period.
The mean number of specialist claims per child was 4.8, while the median was only 2.2.
Median and mean claims for these specialist services by gender and for the first 2 years of age, with median to mean ratios, were:
213 Mean Median Median vs mean
Gender Male 5.4 2.6 51.9% lower
Female 4.2 1.9 55.7% lower
Age < 1 year 1.93 0.48 75.2% lower
1 year 0.62 0.17 72.8% lower
Again, it is seen that the mean number of specialist consultations per child over the 8 years is misleading. It overstates the amount of consultations. The examination of individual claims shows median claims to be very low, as most children had no more than 2 specialist claims during the eight years.
Diagnostic procedures, investigations and imaging
The numbers of diagnostic procedures, investigations and imaging claimed by individual children over the eight-year period are shown in Figure 6.9.
Figure 6.9 Number of diagnostic procedures, investigations and imaging per child,
1990-1997
3000
2500
2000
1500
1000 No. of children
500
0 0 1 to 2 3 to 6 7+
No. of diagnostic procedures, investigations and imaging
214 Forty percent of children made no claim for diagnostic procedures, investigations and imaging
(MBS Groups D1, D2, I1, I2, I3 and I4, MBS Categories 2 & 5). The median was 1.0 compared with a mean of 2.0 per child over 8 years. Median and mean claims for these services for the first 2 years of age and for gender, with median to mean ratios, were:
Mean Median Median vs mean
Gender Male 2.19 1.12 48.8% lower
Female 1.86 0.84 54.9% lower
Age < 1 year 0.35 0.10 71.8% lower
1 year 0.23 0.08 65.1% lower
For X-rays alone (diagnostic radiology - MBS Group I3) median claims per child were 0.4 over 8 years, compared with 1.1 mean claims. Fifty three percent of children made no claim for X-rays over the eight-year period.
215 Pathology services
Individual utilisation of pathology services is shown in Figure 6.10.
Figure 6.10 Number of pathology services per child, 1990-1997
2500
2000
1500
1000 No. of children of No.
500
0 0 1 to 4 5 to 8 9 to 14 15+ No. of pathology services
Almost two-thirds of children (67.2%) had at least one claim for pathology over the eight-year period. While mean claims for pathology (MBS Category 6) were 5.0 per child, the median was lower at 2.4 claims per child. Median and mean claims for these services for the first 2 years of age and for gender, with median to mean ratios, were:
Mean Median Median vs mean
Gender Male 5.0 2.3 53.7% lower
Female 5.0 2.5 50.7% lower
Age < 1 year 1.20 0.21 82.4% lower
1 year 0.52 0.11 78.1% lower
216 Optometrical services
During their first eight years of age, most children (70.1%) made no claim for optometrical services (MBS Groups A9, A10 & A11), while 18.5% made one claim, 6.0% two, and 5.4% of children made three or more claims. The median number of optometrical claims per child over 8 years was 0.2, and the mean 0.6.
Surgical operations
Figure 6.11 shows the number of claims for surgical operations per child during the eight-year period.
Figure 6.11 Number of surgical operations per child, 1990-1997
4500
4000
3500
3000
2500
2000
No. of children 1500
1000
500
0 012+ No. of surgical operations
Most children (63.4%) did not have a surgical operation during the eight years. Mean claims for surgical operations (MBS Group T8) per child was 0.6 over 8 years, while the median was only 0.3.
217 Differences in number of claims by gender of child
When examining children’s MBS claims on an individual basis, the number paid on behalf of males again exceeded that for females. Similar to the findings for average total claims of 62.4 for males and 57.0 for females, median claims for individual males were 52.7 and for individual females 48.9. Total claims per child by gender are shown in Figure 6.12.
Figure 6.12 Total claims per child by gender, 1990-1997
500 450 400 350 300 250 200 150 No. of children of No. 100 50 0
9 9 9 9 9 9 0+ 0-9 0-99 10-19 60-69 70-79 80-89 9 -15 17 20-29 30-39 40-49 50-59 00-10910-11 20-12 30-13 40-14 50 60-16 1 1 1 1 1 1 1 Total claims per child
Male Female
As can be seen in Figure 6.12, fewer males than females had low total claims over the eight years, and more males had high counts. This difference between male and female children was statistically significant (chi-square=36.2, d.f. =11, p <0.001). Males consistently used more services than females, even from their 1st month of life, during which 40% of boys made at least one claim compared with 35% of girls.
In Figure 6.13 total GP consultations claimed by individual male and female children are shown.
218 Figure 6.13 Number of GP consultations per child by gender, 1990-1997
600
500 n 400 Male 300 Female 200 No. of childre 100
0
9 9 9 9 -1 -29 -49 -59 -7 -9 0-9 0 0 0 100+ 1 20 30-3 40 50 6 8 GP consultations per child
More boys had 40 or more claims for general practitioner consultations than girls (chi- square=24.6, d.f. =8, p <0.001) (Figure 5.12).
Boys also made more claims for specialist consultations than did girls (chi-square=64.9, d.f.
=11, p <0.001), and more boys than girls made at least one claim for a surgical operation
(46.1% compared with 26.6%, chi-square=279.4, d.f. =5, p <0.001). There were no significant differences between boys and girls in terms of pathology or optometrical claims.
Number of claims by area of residence
Areas were compared in terms of the number of services used by individual children of the cohort residing in each Area. The proportion of children with claims in excess of the NSW median was determined for each Area, and the odds of this proportion relative to that for the whole of NSW was determined using logistic regression. As explained in Methods, Chapter
4, since the previously determined medians were continuous rather than integer, the proportion of children with claims in excess of the median was not exactly 50.0% for the 219 whole of NSW. For total claims, the NSW median was 50.5 claims (refer to text following
Figure 5.5), and the proportion of children with more than 50.5 claims in the whole of NSW was 50.0%. Table 6.10 shows for each Area the number of children, the proportion of children with claims in excess of the NSW median, and Odds Ratio (99% Confidence
Interval).
Table 6.10 Proportion of children in each Area of residence who had more claims than the NSW median*
Area of residence Number % of Odds Lower Upper p-value of children ratio 99% limit 99% limit children with more in Area claims than median Wentworth 367 64.0 1.774 1.250 2.519 0.0001↑ South Western Sydney 773 63.3 1.716 1.291 2.281 0.0001↑ Western Sydney 671 62.3 1.647 1.228 2.209 0.0001↑ South Eastern Sydney 555 58.6 1.408 1.037 1.912 0.0039↑ Central Sydney 339 51.6 1.064 0.749 1.509 0.6504 Central Coast 282 51.4 1.055 0.727 1.530 0.7114 Illawarra 354 50.8 1.031 0.730 1.456 0.8195 Northern Sydney 601 50.1 Referent* Hunter 503 44.5 0.800 0.586 1.094 0.0660 Mid North Coast 270 40.7 0.685 0.468 1.004 0.0108 Northern Rivers 258 36.0 0.562 0.379 0.834 0.0002↓ Greater Murray 305 35.7 0.554 0.382 0.805 0.0001↓ Macquarie 115 33.9 0.511 0.295 0.886 0.0017↓ Mid Western 190 32.1 0.471 0.300 0.741 0.0001↓ New England 193 29.5 0.418 0.264 0.660 0.0001↓ Southern 202 26.2 0.355 0.223 0.563 0.0001↓ Far West 46 26.1 0.352 0.144 0.857 0.0025↓ New South Wales 6239 50.0
*The proportion of children residing in Northern Sydney who made more claims than the NSW median (50.1% with more than 50 claims) was the closest of the Areas to the proportion for total NSW (50.0%). Hence Northern Sydney was selected as the referent representing NSW in the above logistic regression. ↑Significantly (p<0.01) higher than NSW median ↓ Significantly (p<0.01) lower than NSW median
For total claims, Table 6.10 shows that a greater proportion of children residing in the metropolitan Areas of Western Sydney, Wentworth, South Western Sydney and South Eastern
Sydney exceeded the NSW median number of claims, while, for almost all the rural Areas, a lesser proportion of children exceeded the median.
220
The median number of claims for GP consultations was 40.0 (refer to text following Figure
3.6), and 50.8% of children in NSW had 40 or more claims. Table 6.11 shows for each Area the number of children, the proportion of children with GP claims in excess of the NSW median, and Odds Ratio (99% Confidence Interval).
Table 6.11 Proportion of children in each Area of residence who had more GP claims than the NSW median* Area of residence Number % of Odds ratio Lower Upper 99% p-value of children 99% limit limit children with more in Area claims than median Western Sydney 671 66.9 2.140 1.514 3.025 0.0001↑ South Western Sydney 773 66.6 2.112 1.508 2.959 0.0001↑ Wentworth 367 64.6 1.929 1.303 2.856 0.0001↑ South Eastern Sydney 555 58.6 1.495 1.051 2.127 0.0033↑ Central Sydney 339 55.2 1.302 0.879 1.928 0.0836 Central Coast 282 55.0 1.291 0.855 1.951 0.1102 Illawarra 354 48.6 Referent* Northern Sydney 601 46.8 0.929 0.658 1.313 0.5840 Hunter 503 46.3 0.913 0.638 1.306 0.5131 Mid North Coast 270 40.4 0.716 0.470 1.091 0.0412 Macquarie 115 35.6 0.586 0.331 1.038 0.0161 Greater Murray 305 34.8 0.564 0.373 0.852 0.0004↓ Northern Rivers 258 34.5 0.557 0.361 0.861 0.0005↓ New England 193 31.6 0.489 0.301 0.793 0.0001↓ Mid Western 190 29.0 0.431 0.263 0.707 0.0001↓ Southern 202 25.2 0.357 0.217 0.589 0.0001↓ Far West 46 23.9 0.333 0.131 0.844 0.0023↓ New South Wales 6239 50.8
*The proportion of children residing in Illawarra who made more claims for GP consultations than the NSW median (48.6% with more than 39 claims) was the closest of the Areas to the proportion for total NSW (50.8%). Hence Illawarra was selected as the referent representing NSW in the above logistic regression. ↑Significantly (p<0.01) higher than NSW median ↓ Significantly (p<0.01) lower than NSW median
Again, for GP consultations, Western Sydney, Wentworth, South Western Sydney and South
Eastern Sydney Areas had higher proportions of children exceeding the NSW median, while children living in most of the rural Areas had lower proportions.
221 The median number of claims for specialist consultations was 2.2 (refer to text following
Figure 5.7), and 47.0% of children in NSW had three or more such claims. Table 6.12 shows for each Area the number of children, the proportion of children with more than three specialist claims, and Odds Ratio (99% Confidence Interval).
Table 6.12 Proportion of children in each Area of residence who had more specialist
claims than the NSW median* Area of residence Number % of Odds ratio Lower Upper 99% p-value of children 99% limit limit children with more in Area claims than median South Eastern Sydney 555 60.2 1.760 1.305 2.374 0.0001↑ Northern Sydney 601 57.6 1.580 1.181 2.115 0.0001↑ Wentworth 367 54.2 1.379 0.986 1.929 0.0136 Illawarra 354 52.5 1.289 0.919 1.810 0.0536 Central Coast 282 51.4 1.233 0.855 1.777 0.1412 Hunter 503 49.1 1.124 0.829 1.523 0.3239 South Western Sydney 773 48.6 1.103 0.840 1.448 0.3541 Western Sydney 671 46.2 Referent* Greater Murray 305 42.0 0.842 0.588 1.206 0.2181 Central Sydney 339 41.0 0.809 0.572 1.146 0.1168 Mid North Coast 270 39.6 0.764 0.524 1.115 0.0668 Northern Rivers 258 39.2 0.749 0.510 1.100 0.0529 Macquarie 115 35.6 0.645 0.376 1.107 0.0365 New England 193 33.2 0.578 0.372 0.898 0.0014↓ Mid Western 190 30.0 0.499 0.317 0.786 0.0001↓ Far West 46 37.0 0.683 0.303 1.537 0.2257 Southern 202 28.7 0.469 0.300 0.734 0.0001↓ New South Wales 6239 47.0
*The proportion of children residing in Western Sydney who made more claims for specialist consultations than the NSW median (46.2% with more than 2 claims) was the closest of the Areas to the proportion for total NSW (47.0%). Hence Western Sydney was selected as the referent representing NSW in the above logistic regression. ↑Significantly (p<0.01) higher than NSW median ↓ Significantly (p<0.01) lower than NSW median
Table 6.12 shows that, for specialist services, more children residing in two metropolitan
Areas, Northern Sydney and South Eastern Sydney, exceeded the NSW median number of claims than in NSW as a whole, while in three rural Areas, New England, Mid Western and
Southern, significantly lower proportions of children exceeded the median.
222 The median number of claims for surgical operations was 0.3 (refer to text following Figure
3.10), and 36.6% of children in NSW exceeded this, that is, had at least one surgical operation. Table 6.13 shows for each Area the number of children, the proportion of children with claims for surgical operations in excess of the NSW median, and Odds Ratio (99% C.I).
Table 6.13 Proportion of children in each Areas of residence who had more claims for surgical operations than the NSW median* Area of residence Number % of Odds ratio Lower Upper p-value of children 99% limit 99% limit children with more in Area claims than median Central Coast 282 45.0 1.361 0.923 2.008 0.0411 Wentworth 367 44.7 1.342 0.937 1.923 0.0351 Western Sydney 671 42.9 1.249 0.916 1.705 0.0651 Northern Sydney 601 40.4 1.128 0.819 1.552 0.3326 South Western Sydney 773 39.3 1.077 0.795 1.459 0.5298 South Eastern Sydney 555 38.6 1.043 0.752 1.445 0.7420 Hunter 503 37.6 Referent* Mid North Coast 270 34.8 0.887 0.591 1.331 0.4478 Central Sydney 339 34.5 0.876 0.600 1.278 0.3652 Illawarra 354 34.2 0.863 0.594 1.254 0.3088 Northern Rivers 258 31.4 0.760 0.500 1.156 0.0921 Far West 46 30.4 0.727 0.308 1.716 0.3386 Southern 202 27.2 0.622 0.388 0.996 0.0093↓ Greater Murray 305 26.2 0.591 0.392 0.891 0.0010↓ Macquarie 115 22.6 0.485 0.261 0.903 0.0027↓ New England 193 22.3 0.476 0.287 0.789 0.0002↓ Mid Western 190 22.1 0.471 0.283 0.784 0.0001↓ New South Wales 6239 36.6
*The proportion of children residing in Hunter who had more surgical operations than the median for NSW (37.6% with one or more claims) was the closest of the Areas to the proportion for total NSW (36.6%). Hence Hunter was selected as the referent representing NSW in the above logistic regression. ↑Significantly (p<0.01) higher than NSW median ↓ Significantly (p<0.01) lower than NSW median
Table 6.13 shows that while the proportion of children exceeding the NSW median number of surgical operations was not higher in any Area, the proportions in most rural Areas were significantly lower.
223 DISCUSSION
This analysis has set a baseline for the use of health services by a NSW paediatric population cohort against which the children who have ENT surgery can be compared. The distributions of analytic variables important to this comparison have been examined. The analysis of the
372,815 claims made by an entire cohort of 6239 children from birth until 8 years of age revealed interesting facts regarding population health service utilisation.
These findings have never been reported elsewhere before. The increased likelihood of the need for medical attention among the very young has been indirectly referred to, as in the finding by Nyquist et al that children under 5 years receive 53% of all antibiotic prescriptions in the U.S.52, and in numerous citings of the frequency of otitis media in the first one or two years of life23 41 54 55. However, the monthly rate of use of medical services by a population cohort of children from their date of birth has never been quantified before. The major findings of this analysis were as follows.
The use of medical services is greatest during the first year of life (average 11.4 claims) and declines with increasing age (average 4.9 claims in eighth year). Over the eight-year period, the number of claims decreased exponentially at the rate of 1% per month (or 11% p.a.).
Most MBS claims were for general practitioner attendances (77.3%), with 8.1% being for specialist and consultant physician attendances. Procedures, including surgical operations and claims for anaesthesia, comprised only 1.8% of all claims. Of the 4025 surgical operations, most (48.3%) were trauma-related, namely, wound repair, fractures, dislocations, foreign body removal and burns. Circumcision, hernia or other conditions associated with the
224 neonatal period comprised 14.7% of surgical operations. There were 900 claims for ear, nose and throat surgery, which accounted for 22.4% of surgical operations.
Males made more claims for medical services than females in all categories except optometry and pathology. Many more claims were made during June, July and August, the Australian winter months, than during summer months. This is to be expected - winter is well known as the season for coughs and colds and their sequelae. Children residing in metropolitan areas of
NSW used more health services than those residing in rural areas. There are three probable reasons for this – supply, distance and demand. Supply is the most important of these. Doctors are scarce (it is hard to attract doctors to rural areas)329 and facilities are scarce (with rural populations being much smaller, resources needed to maintain expensive facilities cannot be justified – hence few large hospitals with state-of-the-art capabilities are located in rural
NSW). Distance of many rural locations from those doctors and facilities which are available is the second probable factor. Distance acts as a disincentive to seek medical advice, which leads to the third probable reason – demand. The inconvenience of travelling may result in rural residents having a higher decision threshold for seeking care due to the difficulty of commuting long distances, in contrast with city residents whose medical centre might be only a short trip away.
The average number of claims per child did not reflect individual utilisation patterns. There was a small number of children whose high levels of service utilisation led to higher State averages. Hence the average numbers of claims per child, based on aggregates, overstated utilisation considerably. By contrast, individual patterns of use were better reflected by the
225 median number of claims per child. Over the 8 years the average number of claims per child was 59.8 compared with 50.5, the median. Such differences existed in all claim categories.
For GP services the average was 46.2 claims compared with the median 40.0, specialist services 4.8 compared with 2.2, X-rays 1.1 versus 0.4, pathology 5.0 versus 2.4, optometry
0.6 versus 0.2 and surgery 0.6 versus 0.3.
This analysis of individual Medicare claims has provided a valuable and previously unknown insight into patterns of health service utilisation of NSW children from birth to 8 years of age.
It has shown that the expression of utilisation in terms of aggregates or averages exaggerates the true level of utilisation per child, which is much lower. It has demonstrated important age- and gender-related levels of claims for medical care. It has set a baseline of utilisation for the further analyses. In the next chapter, those cohort children who had ENT surgery will be identified and their utilisation patterns compared with those who did not have such surgery.
226 Chapter 7 CHARACTERISTICS OF COHORT CHILDREN WHO CLAIMED FOR ENT SURGERY
In this chapter, the cohort children who made an MBS claim for privately funded ENT surgery at any time during their first eight years are identified. Their characteristics and the type and number of ENT procedures they underwent are examined.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort surgery compliance: Subsequent utilisation: rates: Results & utilisation: Results & Results & discussion Results & discussion discussion discussion Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort guidelines on Results & utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
227 INTRODUCTION
In the previous chapter the claims history of the whole cohort of children was determined.
The current chapter examines those cohort children who made a claim for ENT surgery at any time during their first eight years, identifying them by re-examination of the matched and de- identified individual records from the HIC cohort data. However, only those whose surgery was privately funded were identifiable in these data. Characteristics of this group, their gender, area of residence and age at surgery are described, as well as the type and combination of ENT surgery. For children who claimed for myringotomy, the number of times such a claim was made was determined.
This cohort of children comprises a sample of the NSW paediatric population. In the descriptive epidemiology section of this research (Chapters 2 and 3), the ENT surgical experience of the whole paediatric population was described. Those members of the cohort who had ENT surgery in each of these years would have been included in this description.
Hence these Medicare data offer the rare opportunity to compare the experience of ENT surgery as recorded for individual children at any time during the study period with that derived on a discrete annual basis from hospital records, which record each occasion of service as if it referred to a separate individual. In this chapter the relationship between population rates of ENT surgery as derived from hospital recorded episodes and rates derived from these longitudinal Medicare claims is explored.
228 METHODS
Study design
In this part of the study, cohort children who made a claim for privately-funded ENT surgery at any time between birth and eight years of age were identified, and their characteristics and experience of ENT surgery described.
Data source and details
The same dataset containing the Medicare records of the cohort of children was used (see
Methods, Chapter 4). As a portion of privately funded surgery is claimable, such ENT surgery appears on the MBS record. Hence it is possible to identify the cohort children who had such surgery. However, cohort children who had ENT surgery as public patients in public hospitals could not be identified, and were necessarily included among children who had not had surgery. The effect of this misclassification is discussed under Limitations. As in the previous epidemiology section, ENT surgery in the context of this study refers to tonsillectomy, adenoidectomy or myringotomy (with or without insertion of drainage tube) or any combination of these operations.
The MBS item numbers which identified ENT surgery were as follows:
Type of MBS code MBS description surgery Tonsillectomy: 41788 G (General TONSILS OR TONSILS AND Practitioner) or ADENOIDS, removal of, in a person 41789 S (Specialist) AGED LESS THAN 12 YEARS Adenoidectomy 41800 G or 41801 S ADENOIDS, removal of Myringotomy 41632 MIDDLE EAR, insertion of tube for DRAINAGE OF (including myringotomy)
229 It can be seen from the above codes and descriptions that the MBS system does not allow tonsillectomy performed as a single procedure to be distinguished from tonsillectomy combined with adenoidectomy. Likewise, the definition for myringotomy does not distinguish between myringotomy, and myringotomy with tube insertion. A child was identified as having had ENT surgery if at any stage during the eight years any of the above codes denoting tonsillectomy, adenoidectomy or myringotomy appeared in the child’s records.
In the area of residence analysis, while some Area administrative boundaries had changed, new Areas were essentially equivalent. They related to Areas described in Chapter 2 Methods as follows.
Broad Old Area Health Service New Area Health Service geographical group Inner Southern Sydney South Eastern Sydney Metropolitan Eastern Sydney Central Sydney Central Sydney Western Sydney Western Sydney Northern Sydney Northern Sydney Outer Wentworth Wentworth Metropolitan South Western Sydney South Western Sydney Central Coast Central Coast Hunter Hunter Illawarra Illawarra Rural Central West Macquarie Mid Western South Eastern Southern South Western North Coast Northern Rivers Mid North Coast New England New England Orana Far West Greater Murray Far West
The definition of Inner Metropolitan, Outer Metropolitan and Rural hence remained the same as described in Chapter 2 Methods.
230 The percentage of children who had had ENT surgery was determined for each new Area
Health Service, as well as NSW children who were resident interstate. Area of residence was defined as residence at the time of each child's final claim. This was due to the difficulty of obtaining suitable denominators for the times of surgery, since these times were spread throughout the eight years.
Statistical analysis
In order to gain a comprehensive picture of the experience of ENT surgery by individual children between birth and 8 years, records of those cohort children who had had ENT surgery were extracted from the full dataset. These were matched according to their arbitrarily assigned identifying numbers and arranged in chronological order for each child. Frequency distributions were obtained for the type, number and combinations of ENT procedures undergone by each child, and gender and area of residence were determined for each child.
Chi-square was used to identify differences between areas in the proportion of cohort children who had ENT surgery. For those who had myringotomy, the number of such claims over the 8 years was counted and tabulated. Age at time of myringotomy was determined as the age at which the first claim for this procedure was made. Differences between results from these individual Medicare claims data and results from the ISC data are shown in percentage form
(but not tested statistically, owing to misclassification of publicly funded ENT surgery patients).
Differences between NSW and Area proportions of children who had surgery were tested
330 using z = |pNSW – pArea|/ √(pNSW.qNSW/nNSW + pArea.qArea/nArea)
231 Poisson regression was then used to test further whether these surgical proportions differed by broad residential group, formed as described in “Data source and details”.
Limitations of the data
Inhospital surgical services provided to children who are public patients of public hospitals do not appear in the HIC data. Such children would then have appeared in the group who did not have ENT surgery. As seen in Chapter 3, during the years 1991/92 - 1993/94, 55-59% of children having ENT surgery were privately funded, with the remainder treated as public patients. However, the presence of these children (approximately 40% of approximately 7% who may have had ENT surgery as public patients) in the comparison group will not affect the testing of hypotheses of difference in health service utilisation between the two groups. If no difference truly exists between the surgery and non-surgery groups, then contamination of the non-surgery group by children who have had surgery does not affect the result. If there is a true difference between the groups then misclassifying surgery children into the non-surgery group would tend to minimize the difference. Hence this misclassification has a conservative bias, and if a difference should emerge empirically it can be accepted as a true difference, which could conceivably be larger if the groups were correctly classified. The effect of misclassification can be estimated using epidemiological methods331
The following example, which measures the association between ENT surgery status and use of medical services, demonstrated the effect of misclassification on the odds ratio.
The variables are:
232 • ENT surgery status: coded 1 if assigned to the surgery group and 0 if assigned to the
non surgery group
• Service utilisation status: since median utilisation was 50 claims (text following Figure
5.5), this was coded 1 for > 50 claims and 0 for < 50 claims over 8 years
Preliminary tabulation of total claims by ENT surgery status for the 6239 cohort children showed:
ENT surgery status Service utilisation status Count 1 1 329 1 0 30 0 1 2881 0 0 2999
However, it is known that there is misclassification in the ENT surgery status variable: the
359 children assigned to the ENT surgery group represent only approximately 60% of all children who had surgery. The true number of cohort children who had surgery would be approximately 598. Hence 239 children were probably misclassified. Supposing these additional children to have had the same proportion (91.6%) of claims >50 as those identified, the above table would become:
True ENT surgery Service utilisation Count status status 1 1 548 1 0 50 0 1 2662 0 0 2979
Using the ENT surgery status as assigned, the table for estimating the odds ratio is:
Had ENT surgery Did not have ENT Total surgery Made 50+ claims 329 2881 3210 Made <50 claims 30 2999 3029 Total 359 5880 6239
The estimated odds ratio = 329*2999/30*2881 = 10.27. 233 The amount of misclassification of the assignment to ENT status is measured by two rates, sensitivity and specificity. As seen above, 239 children are estimated to be misclassified as not having ENT surgery when they did in fact have surgery. Only children whose parents had private health insurance would have had Medicare-claimable surgery. During the period covered by the study, 1990 – 1997, approximately 35% of the population had such insurance.
Hence, of 6239 children in the cohort, which represents a microcosm of the NSW population,
35% or 2184 children would also have had private insurance. Therefore the true situation is estimated as:
Assigned to ENT Not assigned to Total group surgery group Truly had surgery 359 239 598 Truly did not have surgery 0 5641 5641 Total 359 5880 6239
Sensitivity = 359/598 = 0.600
Specificity = 5641/5641 = 1.000
If the table from which the unadjusted odds ratio was calculated is expressed as:
Had ENT surgery Did not have ENT Total surgery Made 50+ claims a b a+b Made <50 claims c d c+d Total a+c b+d a+b+c+d
Then the table for estimating the odds ratio adjusted for misclassification is:
Had ENT surgery Did not have ENT Total surgery Made 50+ claims [b - p2(a+b)]/ [a – p1(a+b)]/ a+b (1- p1 - p2) (1- p1 - p2) Made <50 claims [d - p2(c+d)]/ [c – p1(c+d)]/ c+d (1- p1 - p2) (1- p1 - p2) Total [b+d - np2]/ [a+c - np2]/ n (1- p1 - p2) (1- p1 - p2)
234 Labelling sensitivity p1 and specificity p2, and assigning values p1 = 0.600 p2 = 1.000 a = 329 b = 2881 c = 30 d = 2999, the calculated cell frequencies adjusted for misclassification become:
Had ENT surgery Did not have ENT Total surgery Made 50+ claims 548 2662 3210 Made <50 claims 50 2979 3029 Total 598 5641 6239
From the above table, the odds ratio adjusted for misclassification is estimated to be 12.27.
Since this odds ratio is larger than the non-adjusted estimate of 10.27, it follows that the known misclassification of children who actually have had ENT surgery into the non-surgery group has a conservative effect. If these children had been correctly classified and displayed similar characteristics to the children who had Medicare-claimable surgery, the odds ratio would have been larger. Misclassification tended to minimise differences between the surgery and non-surgery groups. Hence any differences found can be accepted as true differences.
235 RESULTS
How many claims for ENT surgery were made and on behalf of how many children?
As seen in Chapter 5, the 6,239 children in the cohort made 372,815 MBS claims over the eight years. Of these, 581 claims were for tonsillectomy, adenoidectomy or myringotomy.
These claims, which were for privately rather than publicly funded surgery, a portion of which was claimable under Medicare, were made on behalf of only 359 children.
Of these 359 children, 149 had tonsillectomy or tonsillectomy and adenoidectomy, 111 had adenoidectomy and 232 myringotomy. This sum exceeds the number of children, due to some children having more than one type of ENT surgery.
Age at which ENT surgery was performed
The number and rate per thousand cohort children who had each type of ENT surgery by age at time of surgery is shown in Table 7.1.
236 Table 7.1 Number and rate per thousand cohort children who had ENT surgery by surgery type and age at time of surgery
Age at time Tonsillectomy or Adenoidectomy Myringotomy (first) of surgery Tonsillectomy/ Adenoidectomy Number Rate per Number Rate per Number Rate per who had thousand who had thousand who had thousand surgery cohort surgery cohort surgery cohort children children children < 1 year 0 0.0 (0.0,0.0) 1 0.2 (-0.2,0.5) 10 1.6 (0.6,2.6) 1 year 1 0.2 (-0.2,1.5) 8 1.3 (0.4,2.2) 46 7.4 (5.3,9.5) 2 years 13 2.1 (1.0,3.2) 16 2.6 (1.3,3.8) 34 5.4 (3.6,7.3) 3 years 34 5.4 (3.6,7.3) 32 5.1 (3.4,6.9) 47 7.5 (5.4,9.7) 4 years 37 5.9 (4.0,7.8) 19 3.0 (1.7,4.4) 34 5.4 (3.6,7.3) 5 years 28 4.5 (2.8,6.1) 16 2.6 (1.3,3.8) 34 5.4 (3.6,7.3) 6 years 21 3.4 (1.9,4.8) 8 1.3 (0.4,2.2) 15 2.4 (1.2,3.6) 7 years 15 2.4 (1.2,3.6) 11 1.8 (0.7,2.8) 12 1.9 (1.8,3.0) Ages 0-7yrs 149 23.9 111 17.8 232 37.2 (20.1,27.7) (14.5,21.1) (32.5,41.9)
The most common age for tonsillectomy/tonsillectomy & adenoidectomy was 4 years, for adenoidectomy alone 3 years and for myringotomy 3 years.
Type of ENT surgery
Numbers and percentages of children who had each type or combination of ENT surgery are shown in Table 7.2.
237 Table 7.2 Number of children who had ENT surgery during their first eight years by type and combination of surgery
Type of ENT surgery Number (%) of children Rate/1,000 cohort children (95% C.I.) Tonsillectomy or 100(27.8) 16.0 (12.9,19.1) Tonsillectomy & adenoidectomy Adenoidectomy only 27(7.5) 4.3 (2.7,6.0) Myringotomy & tonsillectomy 123(34.3) 232(64.6) 7.9 19.7 37.2 or 49(13.6) (5.7,10.0) (16.3,23.2) (32.5,41.9) Myringotomy & tonsillectomy & adenoidectomy Myringotomy & 74(20.6) 11.9 adenoidectomy (9.2,14.5) Myringotomy only 109(30.4) 17.5 (14.2,20.7) All ENT surgery 359(100.0) 57.5 (51.8, 63.3)
Among this cohort, the most prevalent type of ENT surgery was myringotomy, with 232 cohort children (65%) having had this procedure, either alone or as well as another ENT procedure. More than half of the children who had myringotomy had tonsillectomy or adenoidectomy as well. Of these 123 children, 87 (70.7%) had both types of surgery on the same day. In all but 5 of the remaining 36 children, myringotomy was the earlier operation, followed by tonsillectomy or adenoidectomy, at least a year later in most cases.
Due to the absence of a unique MBS code, it was impossible to determine the number of children who had tonsillectomy only, without adenoidectomy.
Number of claims for myringotomy
Many children who had myringotomy made more than one claim during the study period.
Table 7.3 shows the number of claims for myringotomy per child among those who had this operation. 238 Table 7.3 Number of claims for myringotomy per child Number of claims for Number of children % of children myringotomy 1 174 75.0 2 41 17.7 3 13 5.6 4 1 0.4 5 2 0.9 8 1 0.4 Total children 232 100.0
Of the 232 children who had myringotomy, one in four had repeat operations.
Gender of children who had ENT surgery
Of the 3,194 male and 3,045 female children in the cohort, 226 males and 133 females claimed at least once for ENT surgery over the 8-year period. This yielded a rate of ENT surgery of 70.8/1000 males, significantly higher than the female rate of 43.7/1000 (chi- square=21.079, d.f. =1, p<0.001), and a male/female ratio of ENT surgery of 1.62:1.
The amount of ENT claims per child did not differ by gender: the 226 males made 362 claims for ENT surgery, while the 133 females made 219 claims, yielding, on average, 1.60 ENT claims per male and 1.65 per female child.
Type and combination of surgery by gender of child
In Table 7.4 the type of surgery undergone by males and females is compared. In this table the combination, myringotomy with tonsillectomy and/or adenoidectomy, was considered as a group.
239
Table 7.4 Type and combination of ENT surgery by gender of child
Type and combination of ENT surgery Males Females Number % Number % Tonsillectomy or 59 26.1 41 30.8 Tonsillectomy & adenoidectomy Adenoidectomy only 16 7.1 11 8.3 Myringotomy only* 72 31.9 37 27.8 Myringotomy & tonsillectomy or 79 35.0 44 33.1 Myringotomy & tonsillectomy & adenoidectomy or Myringotomy & adenoidectomy All ENT surgery 226 100.0 133 100.0 * Regardless of number of myringotomies
Males did not differ from females in type or combination of ENT surgery performed over the
8 years(chi-square=1.363, d.f. =3, p=0.714). In Table 6.4, ‘Number’ refers to individual children. Hence if a child claimed at any time during the 8 years for any combination of surgery shown in the first 3 rows, he/she would be counted as having had one of the 4th row’s combinations.
Area of residence
Table 7.5 shows the number and percentage of children who had ENT surgery during the eight years according to their Area of residence at the time of the final claim.
240 Table 7.5 Percentage of children who had ENT surgery during the eight years by area of residence at time of final claim
Area of residence Number of children Total cohort % of children who who had ENT children in Area had ENT surgery surgery Northern Sydney 55 601 9.2↑ Central Coast 26 282 9.2↑ Illawarra 28 354 7.9 Central Sydney 26 339 7.7 Wentworth 26 367 7.1 Southern 13 202 6.4 New England 11 193 5.7 South Western Sydney 41 773 5.3 South Eastern Sydney 28 555 5.0 Western Sydney 33 671 4.9 Hunter 24 503 4.8 Far West 2 46 4.4 Mid Western 8 190 4.2 Greater Murray 12 305 3.9 Mid North Coast 9 270 3.3↓ Interstate 7 215 3.3 Northern Rivers 7 258 2.7↓ Macquarie 3 115 2.6↓ All children 359 6239 5.8 ↑ % significantly higher (p<0.01) than NSW average ↓ % significantly lower (p<0.01) than NSW average
The percentage of cohort children who had ENT surgery differed significantly by Area of residence (chi-square=43.054, d.f. =17, p<0.001). To determine which Areas contributed to this result, differences between Area proportions and the NSW proportion were tested. At the
95% confidence level, both Northern Sydney and Central Coast had significantly higher percentages of children who had undergone ENT surgery than average NSW, while percentages in Northern Rivers, Mid North Coast and Macquarie were significantly lower than average.
To gain a better overall picture of these differences, Areas were aggregated into three broad groups, Inner Metropolitan, Outer Metropolitan and Rural, as defined in Methods. Areas grouped under these broad areas of residence share similar characteristics, such as distance
241 from population centre, size of population and availability of medical resources, as described in Chapter 2.
To examine whether the differences found between the Areas in the proportion of children who had surgery persisted when grouped in this way, Poisson regression was used. Table 7.6 shows the results of this broad residential group comparison.
Table 7.6 Percentage of children who had ENT surgery during the eight years by broad residential group
Broad % of children who had ENT surgery Significance level of residential difference from group Lower 95% Estimate Upper 95% Inner metropolitan C.I C.I. area Inner 5.6 6.6 7.7 Base metropolitan Outer 5.4 6.8 9.3 n.s. metropolitan Rural 3.1 4.1 5.5 P<0.001
In Table 7.6 it can be seen that experience of ENT surgery by children residing in Outer
Metropolitan areas did not differ significantly from that of children residing in Inner
Metropolitan areas (6.8% and 6.6% respectively). In contrast, only 4.1% of children residing in Rural areas had ENT surgery over the eight years, significantly fewer than in the other areas (p<0.001).
Combinations of ENT surgery did not differ by broad area of residence.
Relationship between ISC and HIC data
These HIC data relate to a cohort of children who comprise a subset of the NSW population, those born during January 1990, and describe all their Medicare claims for their first 8 years 242 of age as well as details regarding their experience of privately funded ENT surgery. The ISC data (described in Chapters 2 and 3) relate to the total population of NSW children, but only to their ENT surgery inhospital episodes. Hence the HIC cohort children who had privately funded ENT surgery would form a small part of the ISC data, but their individual experience would be more complete (since the ISC data relates only to episodes and does not match children).
It was considered valuable to compare surgery rates from the two sources, partly to validate the HIC data as a small subset of the ISC data, and also to determine the extent of the limitations of the ISC data in considering episodes of hospitalisation rather than individual children. In the ISC lifetable analysis of 1989/90 rates, the risk of a NSW child having ENT surgery by the age of eight years was estimated to be 14.7% (Table 3.6). This ISC year was used in this comparison, being close to the date of birth of the cohort, January 1990. The lifetable estimate was then compared with the actual prevalence of surgery among the HIC cohort. In this cohort, while 581 ENT procedures were claimed over the 8 years by 6239 children, these related to only 359 children, as some children claimed for more than one ENT procedure (Table 7.2), and some had more than one myringotomy procedure (Table 7.3).
Hence these HIC data show that 5.8% of these cohort children had ENT surgery by their eighth year of age, a significantly lower percentage than estimated from the ISC data.
However, this cohort analysis reflects only Medicare-claimable surgery, that is, privately funded surgery with a portion of the surgeon’s fee claimable. In Chapter 3 Results, where all
ENT surgery, whether privately or publicly funded, was analysed, it was seen that in the years
243 1991/92, 1992/93 and 1993/94 the percentage of NSW children who had an ENT procedure and were insured or privately funded was 59.1%, 58.2%, and 56.8% respectively. For most of the period during which the cohort was followed, 1990 – 1997, the privately funded percentage of ENT surgery could be estimated at 57% to 60%. Another source of discrepancy would be that the ISC data counts episodes rather than individuals. If each of the 581
Medicare claims made by the 359 children were to be counted as individuals, as presumably might happen to records of these children in the ISC data if their dates of surgery were not concurrent, then the percentage who had surgery becomes 9.3%. If this 9.3% is then considered to represent 57%-60% of total ENT surgery, private and public, this yields 15.5%, reasonably close to the ISC 1989/90 estimate of 14.7% (Table 3.6). Hence this comparison highlights the amount of overestimation inherent in the ISC data (and underlying much of epidemiology based upon hospital data) due to the counting of episodes rather than children.
This amount of overestimation could be as much as 9.3/5.8 or 60%.These comparisons can be considered of value as a test of validity for both sets of data.
Further comparisons of ISC and HIC cohort results were made for tonsillectomy and myringotomy separately. (In this and following Tables, children’s ages are not precisely comparable, since in the ISC analysis age refers to age during the financial year, July to June of the following year, and for the HIC cohort to calendar year, January to December.)
The availability of consecutive years of ISC data had allowed the calculation of actual surgical rates for successive cohorts of all NSW children in successive years for their first five years of age (Tables 3.14 and 3.15). Accordingly these rates were accumulated for successive years for the 1989/90 cohort and compared with rates of the HIC cohort (which, being born in 244 January 1990, formed part of the 1989/90 NSW population). The tonsillectomy comparison is shown in Table 7.7.
Table 7.7 Actual experience of tonsillectomy: HIC cohort compared with NSW ISC cohort aged <1 year in 1989/90
Age of child % of HIC cohort who had % of ISC cohort who had HIC as % of ISC privately funded tonsillectomy tonsillectomy By age 1 year 0.00 0.00 n.a.
By age 2 years 0.02 0.09 18
By age 3 years 0.22 0.43 53
By age 4 years 0.77 1.29 60
By age 5 years 1.36 2.41 57
In the case of tonsillectomy, since it is performed once only, there is no risk of overestimation in the ISC data through treating episodes as individuals. Hence the column expressing actual
HIC experience as a percentage of ISC estimated risk of total surgery represents privately funded as a percentage of total tonsillectomy. For children aged under 3 years, this percentage is very low, meaning that most children of this age would have their tonsillectomy as public patients, where the threshold for surgery is possibly higher. Table 6.9 shows that the HIC to
ISC percentages closely resemble what is already known about the proportion of privately funded ENT surgery in the years 1991/92 to 1993/94 (Chapter 3 Results), which serves to validate both sets of data.
In Table 7.8, prevalences of myringotomy among the NSW population cohort aged under 1 year in 1989/90 are compared with the experience of the HIC cohort.
245 Table 7.8 Actual experience of myringotomy: HIC cohort (born January 1990) compared with NSW ISC cohort < 1 year in 1989/90
Age of child % of HIC cohort who had % of 1989/90 ISC cohort HIC as % of ISC privately funded who had myringotomy myringotomy By age 1 year 0.16 0.25 64
By age 2 years 0.90 1.41 63
By age 3 years 1.44 2.51 57
By age 4 years 2.20 4.08 54
By age 5 years 2.74 5.85 47
Table 7.8 shows that privately funded myringotomy comprised about 60% of the total until
1994 when the children were aged 4 years, after which it dropped below 50%. Hence, for myringotomy, the younger children who had this procedure were more likely to be privately funded. The discrepancy could also include overestimation of ISC rates, since members of the
ISC cohort might have been counted more than once if they had a repeat insertion of tubes.
246 DISCUSSION
Information regarding this cohort was extracted from a completely different dataset (HIC) from the inhospital data (ISC) used in the epidemiological surgery analysis (Chapters 2 and
3). However, children identified in this cohort as having had ENT surgery comprise a subset of all NSW children who were admitted to hospital for ENT surgery and described in the ISC analysis. Theoretically it would be possible to track these cohort children through successive
ISC years by examining their dates (or months) of birth, but such tracking was precluded on the grounds of confidentiality.
Nevertheless, the cohort children remain part of these inhospital ENT surgery data. How do these results from the HIC data compare with the ENT surgery inhospital analysis? In the HIC cohort 5.8% of children were found to have had privately funded ENT surgery by 8 years of age (Table 7.2). In order to compare this percentage with that obtained from the ISC hospital- based population data, this percentage needs to be adjusted to the known overestimation inherent in the ISC data, which relate to episodes of hospitalisation rather than children
(Limitations, Chapter 2). The amount of this overestimation is probably 60%, according to the current HIC analysis of individual children where ENT claims (581) exceeded the number of individuals (359) by this amount. Also adjusting for public surgery, estimating the proportion of privately funded ENT surgery at 60%, the expected percentage becomes 15.5% for all ENT surgery, public and private. This is comparable to the 14.7% obtained through applying cross- sectional lifetable methods to the 1989/90 ISC data, providing a measure of validity to both sets of data. However, this comparison highlights the dangers of overestimation where individuals cannot be followed over a period. As in the current case, this could result in overestimation of prevalence by as much as 60%. 247 Procedure type and combination proportions of the cohort children show that the most prevalent type of surgery was myringotomy, and that more than half the children who had myringotomy had adenoidectomy and/or tonsillectomy as well. Not all combinations occurred on the same day, unlike the combinations derived from the hospital data. Some cohort children who had more than one procedure had the second procedure years later, rather than during the same hospital episode. Again, it is valuable to be able to derive this kind of information about the true proportion of children having more than one ENT procedure.
Regarding gender, again the two sets of data did not yield exactly similar results, due to children rather than procedures and different time spans being counted. However, in the ISC age and gender specific rates (ISC Tables 3.8, 3.10, 3.12), the male/female ratio for age 0-4 years in 1993/94 was 1.47:1 for myringotomy, 1.38:1 for tonsillectomy and 1.46:1 for adenoidectomy, which is reasonably compatible with the ratio of 1.6:1 obtained for all cohort children who had ENT surgery over the 8 years, 1990 – 1997.
The analysis in this Chapter has yielded information which has not previously been reported for Australian children, that is, the number of privately funded myringotomy procedures undergone by an individual child. From the cohort data, each myringotomy claimed for was identifiable. Hence, these data have established that 25% of children who claimed for myringotomy made at least 2 claims, with 7.3% claiming for three or more of these procedures. This proportion of reinsertions is slightly higher than in the U.S., where 19.9% of children who underwent tube placement between April 1995 and May 1998 had had a second
248 set of tubes placed by May 2000332: however, the comparison is probably even closer, since in the latter study only 2 years of follow-up were allowed for some children.
In the current study, the comparison of two sources of surgical data demonstrates that the picture of paediatric ENT surgery which forms the usual basis of epidemiological knowledge is distorted. From routine hospital data, rates are based on episodes rather than children. In the current analysis of Medicare data, individual children have been tracked through the years during which they are most likely to have ENT surgery. The analysis has added valuable information. The exact number and combination of procedures undergone by individual children has been determined.
When combined with knowledge of the proportion of the population privately insured, far better estimates of the proportion of children at risk of ENT surgery have been determined.
Applying a rate per thousand rather than a percentage, 16.02/1000 of the cohort children had had privately funded tonsillectomy or tonsillectomy with adenoidectomy by the end of their
8th year, 4.3/1000 had had adenoidectomy, 7.85/1000 had myringotomy and tonsillectomy or all three procedures, 11.86/1000 had myringotomy and adenoidectomy, and 17.47/1000 children had myringotomy only. Since these exclude public procedures, adjustment by the public/private ratio would yield a far more reliable estimate or the true surgery rates than is known using hospital data as the source of information. For this population cohort, assuming the privately funded component to be 60% of total ENT surgery, rates by the age of 8 years become 26.7/1,000 for tonsillectomy or tonsillectomy with adenoidectomy, 7.2/1000 for
249 adenoidectomy, 13.1/1000 for myringotomy and tonsillectomy or all three procedures,
19.8/1000 for myringotomy and adenoidectomy, and 29.1/1000 for myringotomy only.
In the next chapter use of health services by this group of children will be compared with the group of cohort children who did not have privately funded ENT surgery.
250 Chapter 8 COMPARISON BETWEEN CHILDREN WHO HAD ENT SURGERY AND THOSE WHO DID NOT
In this chapter, the utilisation of health services between birth and eight years of age by cohort children who had ENT surgery is compared with the utilisation by children who did not have surgery.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort surgery compliance: Subsequent utilisation: rates: Results & utilisation: Results & Results & discussion Results & discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort Results & guidelines on utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
251 INTRODUCTION
In the previous chapter, those cohort children who had (Medicare-claimable) ENT surgery during their first eight years were identified and their experience of such surgery between birth and 8 years of age determined. In the current chapter, the utilisation of health services by these children was examined. Their patterns of utilisation of medical services prior to surgery were compared with those of the cohort children who did not have surgery.
In this comparison, the null hypothesis was that no difference exists between the groups. Such a finding would imply that variation in rate of surgery is attributable to other factors such as physician opinion. However, a difference would be expected. These children would be expected to use a greater amount of medical services prior to surgery, due to the ENT-related conditions that resulted in its performance. A failure to find a difference between the groups would lend weight to the conclusion that the child’s medical condition is not the major factor underlying the surgical decision, but rather the physician’s belief in the superior efficacy of surgery over other forms of treatment.
Before performing a more complex analysis, it was considered useful to determine whether crude differences between the groups, both in overall claims and by type of service, existed.
Hence an initial comparison of total medical claims by type of claim over the 8 years between children who had and did not have surgery was made. In this crude comparison it was not possible to limit claims of the surgery group to the pre-surgery period, as for each individual child the amount of time pre-surgery varied.
252 METHODS
Study design
In this part of the study, the pre-surgery use of health services by children identified as having received ENT surgery at any time between birth and eight years of age is compared with patterns of use by children who did not have this surgery. The null hypothesis was that no difference in utilisation of health services would be found.
Data source and details
The same HIC dataset described in Chapters 4-6 was accessed and used as the basis for creating new data files. The first file contained 96 records for each child, that is, 6239 x 96 =
598,944 records. Each record contained counts of claims made in each of the 96 months
(with value 0 if no claim in month j), as well as a variable indicating whether the child had had ENT surgery and a flag for each surgery type indicating the two months before surgery, the month of surgery and the two months following surgery. The record for each month then contained six perisurgery variables for each of tonsillectomy, adenoidectomy and myringotomy, with value 0 if the month was not a perisurgery month and 1 if it was. Hence these 18 variables all had value 0 for each month of the 5880 children who did not have ENT surgery, while, for children who did have surgery, these variables had value 1 for only the relevant perisurgery months, which differed for each of these children.
From this was created another file in which the records of the children who had surgery were limited to their individual pre-surgery periods (assumed to be prior to a perisurgery period beginning 2 months before surgery). While this second file contained the full complement of records for each of the 96 months for each child who did not have surgery (5880 x 96 =
253 564,480 records), the number of records held in the file for children who had surgery varied by child from 1 to j-2, where j indicates the month of surgery. Hence, the total number of pre- surgery records for this group of children was 17,398 (instead of the full complement which would have been 359 x 96 = 34,464 records), yielding a total of 581,546 records in the file.
Statistical analysis
Bivariate analysis
This was a preliminary analysis to gain an overall picture of any differences between surgery and non-surgery groups, and to see whether any such differences varied by type of medical service. In these preliminary comparisons it was not possible to compare only the pre-surgery claims made by the surgery group since the pre-surgery periods differed by child, whereas the period in which total claims could be accumulated for the children who did not have surgery was a constant eight years. Expressed algebraically:
n 96 For the non-surgery group, total claims = Σ i Σ j claims ij
n m For the surgery group, total claims = Σ i Σ j claims ij
Total claims made over the eight years by individual children in each group were counted under the following broad headings of medical services - total claims, GP consultations, specialist consultations, diagnostic tests, pathology tests and optometry. Means, medians and proportions were calculated for each group. Comparisons between the two groups were made using crosstabulations, proportions and means, and differences tested using the z-test, t-test and chi-square.
254 Multivariate analysis
As explained above, the bivariate analysis compared the groups with regard to total claims over the eight years, rather than limiting the period for the surgery group to that which was prior to surgery. To determine whether the pattern of claims by month since birth differed between the groups when only the period pre-surgery was included in the surgery group, a multiple linear regression analysis333 was performed. This analysis took into account the age of the child.
The new data file created for this analysis has been described in the Data Source section. This file contained one record for each non-surgery child for each of the 96 study months, and one record for each child who had surgery only for each pre-surgery month. Each record contained a count of the number of claims made by the child in each month, with value 0 if no claim was made (CLAIMS). Each record contained a dummy variable (ENT status) identifying whether the child had claimed for any type of ENT surgery at least once during the 8 year period with value 1 and value 0 otherwise. Each record contained the month number, from 1 to 96 (or, in the case of the surgery group, from 1 to the second month pre- surgery). As month number also represented the child's age in months, this variable was designated AGE.
The number of claims in each month (CLAIMS) comprised the dependent variable in the linear regressions. AGE was the independent variable, which tested whether age of child affected the number of claims, that is, whether there was a trend in claims over time. The dummy variable indicating whether the child had had ENT surgery at all (ENT) comprised the
255 comparison variable. An interaction term between this variable and age (ENT *AGE) was calculated to determine whether any trend in claims over time was the same for both groups.
The model used in this linear regression was:
CLAIMS = AGE + ENT + ENT*AGE
Limitations of the data
As shown in Chapter 6, Limitations of the data, although there is known misclassification of children who had publicly-funded surgery into the non-surgery group, the influence of this misclassification was found to be conservative. Hence, in the following comparative analysis, all those children not identified in these Medicare data as having had surgery were treated as if they belonged to the non-surgery group. Although approximately 239 of the 5880 children so assigned were probably misclassified, this group is henceforth referred to as children who did not have surgery, although this designation is not strictly correct.
256 RESULTS
Bivariate analysis
Comparison of total claims over the full 8 years by both groups showed that the children who had ENT surgery used more health services than those who did not have surgery. Table 8.1 shows the average number of claims made over the eight years by each group.
Table 8.1 Average number of MBS claims made over eight years by children who did or did not have ENT surgery Type of claim Total Average claims Z score P value claims (difference Children who Children who between had ENT did not have groups) surgery ENT surgery All claims 372815 103.8 57.1 21.064 <0.0001
GP consultations 288347 67.2 44.9 13.670 <0.0001 Specialist 30242 13.2 4.3 20.990 <0.0001 consultations Total children 359 5880
In Table 8.1 it is seen that average total MBS claims made by children who had ENT surgery over the eight years was almost double that of those who did not have surgery. More claims were also made for GP and specialist consultations.
Further examination of the data showed that this discrepancy was evident from birth. In their
1st month of age, 61% of the surgery group compared with 36% of the non-surgery group made at least one claim for a health service.
In the two following tables, owing to skewness found in these distributions of individual children’s claims, medians and quartiles for each group were also calculated.
The distribution of claims per child for GP consultations by ENT surgery status is shown in
Table 8.2.
257 Table 8.2 Claims for GP consultations per child during the eight years by ENT surgery status Parameter Children who had ENT Children who did not surgery Mean per child 67.2 44.9 1st quartile 43.8 24.4 Median 62.3 38.4 3rd quartile 83.8 57.1 Number of children 359 5880
The average is higher than the median due to skewness. The median number of claims for GP consultations for the children who had ENT surgery was 62, that is, half of these children made more than 62 claims over the eight years. One quarter made over 83 claims. By contrast, only one quarter of the control group made over 57 claims.
The distribution of claims per child for specialist consultations by ENT surgery status is shown in Table 8.3.
Table 8.3 Claims for specialist consultations per child during the eight years by ENT surgery status Parameter Children who had ENT Children who did not surgery Mean per child 13.2 4.3 1st quartile 4.8 0 Median 8.9 1.5 3rd quartile 16.2 4.9 Number of children 359 5880
Half of the children who had ENT surgery made more than 8 claims for specialist consultations over the eight years, and one quarter made over 16 claims. By contrast, only half of the controls made more than 1 claim for a specialist consultation. These differences between the groups persisted for other health services.
Table 8.4 shows the distribution of claims per child for optical services over the eight years.
258 Table 8.4 Total optical claims per child over eight years by ENT surgery status Number of optical claims Children who had ENT Children who did not surgery Number % Number % 0 211 58.8 4162 70.8 1 85 23.7 1071 18.2 2+ 63 17.6 647 11.0 All children 359 100.0 5880 100.0
While most children in both groups did not make a claim for optometry over the eight years,
41.2% of children who had ENT surgery made at least one such claim compared with 29.2% of those who did not have surgery (chi-square=25.147, d.f.=2, p<0.001).
Table 8.5 compares children who had ENT surgery and those who did not in terms of claims for diagnostic tests over the eight years.
Table 8.5 Total diagnostic tests per child over eight years by ENT surgery status Number of diagnostic tests Children who had ENT Children who did not surgery Number % Number % 0 34 9.5 2476 42.1 1 40 11.1 1219 20.7 2 39 10.9 778 13.2 3 37 10.3 451 7.7 4+ 209 58.2 956 16.3 All children 359 100.0 5880 100.0
Children who had ENT surgery made more claims for diagnostic tests over the eight years than did those who did not, with 58.2% making 4 or more such claims compared with only
16.3% of the controls (chi-square=428.460, d.f.=4, p<0.001).
Total X-ray claims (a subgroup of diagnostic tests) are compared by group in Table 8.6.
259 Table 8.6 Total X-rays per child over eight years by ENT surgery status Number of X-rays Children who had ENT Children who did not surgery Number % Number % 0 116 32.3 3180 54.1 1 78 21.7 1275 21.7 2 56 15.6 681 11.6 3 32 8.9 314 5.3 4+ 77 21.5 430 7.3 All children 359 100.0 5880 100.0
Again, children who had ENT surgery had more X-rays over the eight years than those who did not have ENT surgery, with 21.5% making at least 4 such claims compared with only
7.3% of the controls (chi-square=125.959, d.f. =4, p<0.001).
Table 8.7 shows the number of pathology claims made by children who had ENT surgery in comparison with those who did not.
Table 8.7 Total pathology claims per child over eight years by ENT surgery status Number of pathology claims Children who had ENT Children who did not surgery Number % Number % 0 39 10.9 2007 34.1 1 10 2.8 334 5.7 2 27 7.5 803 13.7 3 24 6.7 392 6.7 4+ 259 72.1 2344 39.9 All children 359 100.0 5880 100.0
Children who had ENT surgery made more pathology claims over the eight years than those who did not, with 72.1% making at least 4 such claims compared with 39.9% of the controls
(chi-square=155.086, d.f.=4, p<0.001).
In summary, in this simple analysis of gross claims, it was found that children who underwent
ENT surgery made more Medicare claims over the 8 study years than those who did not undergo surgery, and this was true in all categories of claim. However, this analysis did not
260 consider other factors that might account for this finding. These were considered in the multivariate analysis with the following results.
Multivariate analysis
In the preceding bivariate analysis, children who had ENT surgery were found to have made more claims over the eight years than those who did not have surgery. One hypothesis is that such an excess of claims would be confined to the pre-surgery period. It is also possible that the excess of claims found might have been due to the extra services directly related to surgery, its lead up and its aftermath.
In the multivariate linear regression analysis, the two groups were compared in terms of number of claims per month of age, since, from the whole cohort analysis (Chapter 4), it was known that claims diminished by age of child. In this comparison, for the surgery group, only those months falling into each individual child’s pre-surgery period were compared with the non-surgery group. Results of this analysis are presented in Table 8.8.
Table 8.8 Estimated MBS claims by month of age: non-surgery group compared with surgery group prior to surgery
Parameter Interpretation Parameter Standard P value estimate error Intercept Number of claims at month 1 0.87492 0.00342 <0.0001 AGE Change in number of claims per month -0.00578 0.00006 <0.0001 ENT Adjustment to claims at month 1 for ENT 0.52257 0.01435 <0.0001 group AGE*ENT Adjustment to change per month for ENT -0.00315 0.00026 <0.0001 group R2 = 0.0208
261 The interpretation of the linear regression results shown it Table 7.8 is as follows. The non- surgery group made on average 0.87492 claims for medical services in their first month of age. This declined slowly by age. On average, they made 0.87492-0.00578=0.86914 claims in their second month, 0.87492-2x0.00578=0.86336 in their third month and so on. By contrast, the surgery group made 0.87492+0.52257=1.39749 claims in their first month, but these declined at a faster rate of -0.00578-0.00315=-0.00893 claims per month, so that in their second month their average claims were 1.39749-0.00893=1.38856 claims, in their third month 1.39749-2x0.00893=1.37963 claims and so on.
Evaluation in this manner for the whole 96 months was continued, resulting in a complete set of estimated claims for each surgery group. This was done so as to determine, in view of the steeper decline in number of claims per month among the surgery group, whether convergence between the groups occurred at some point. It was also considered useful to determine actual observed claims by month and group to examine how well the regression model fitted the observations. Accordingly, mean observed claims for each month of age by surgery group were calculated. However, in the surgery group, because the months relating to this group in this dataset only represented the children who had not yet had surgery, there was a continual depletion of numbers contributing to these means, so that towards the end of the
96 months there were very few children left in the group. For those months when the number of such children dropped below 20 the means were disregarded as probably unreliable.
Results are plotted in Figure 8.1, which illustrates the match between the estimates (trends) and mean observed claims.
262 Figure 8.1 Observed and estimated mean MBS claims by month of age and surgery group: children who had ENT surgery, prior to surgery, compared with those who did not have surgery
3
h 2.5
2
1.5
1
0.5 Average claims per mont Average claims per
0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 Age (months)
No ENT surgery: observed No ENT surgery: estimated ENT surgery (pre): observed ENT surgery (pre): estimated
In Figure 8.1 it is seen that the estimated lines express the direction of the observed means well, except for the area beyond month 60 for the surgery group. After month 60 the number of surgery group children who had not yet had surgery, upon which the estimates were based, had become very small (in months 60, 70 and 80 there were only 103, 58, and 32 such children respectively, compared with 313, 282 and 228 in months 20, 30 and 40 respectively).
Figure 8.1 shows that, although the monthly decline in claims was greater for the surgery group, the groups never converged. Prior to having surgery, these children used more health services from birth than children who had no surgery.
263 The strength of this difference between the surgery and non-surgery groups was considered sufficient to constitute a potential test for risk of ENT surgery. Accordingly, from the regression results in Table 8.8, 99% confidence intervals were calculated for each estimated monthly total. Total annual estimated claims were obtained by summing individual monthly estimated totals.
The results for each group are shown in Table 8.9.
Table 8.9 Annual estimated total claims for surgery and non-surgery groups Age of child Children who had ENT surgery Children who did not have ENT surgery Estimated claims 99% C.I. Estimated claims 99% C.I.
1-12 months 16.1 15.3-16.8 10.0 9.9-10.2
13-24 months 14.8 13.8-15.7 9.2 9.1-9.4
25-36 months 13.5 12.3-14.7 8.4 8.2-8.5
37-48 months 12.2 10.9-13.6 7.6 7.4-7.7
49-60 months 10.9 9.4-12.5 6.7 6.5-6.9
61-72 months 9.6 7.9-11.4 5.9 5.7-6.1
73-84 months 8.4 6.4-10.3 5.1 4.8-5.3
85-96 months 7.1 4.9-9.2 4.2 3.9-4.5
By consulting Table 8.9, it can then easily be determined whether any actual total claims for a specific year of age fall within the limits of the not-at-risk group. To further simplify this distinction, annual totals were accumulated, so that totals for several years of claims could be compared for group allocation (Table 8.10).
264 Table 8.10 Estimated cumulative claims by specified ages by surgery status Age of child Children who had ENT surgery Children who did not have ENT surgery Estimated claims 99% C.I.s Estimated claims 99% C.I.s
By age 1 year 16.1 15.3-16.8 10.0 9.9-10.2
By age 2 years 30.9 29.2-32.6 19.3 19.0-19.5
By age 3 years 44.4 41.5-47.2 27.6 27.2-28.1
By age 4 years 56.6 52.4-60.8 35.2 34.6-35.8
By age 5 years 67.5 61.7-73.3 41.9 41.1-42.7
By age 6 years 77.2 69.6-84.7 47.8 46.8-48.8
By age 7 years 85.5 76.0-95.0 52.9 51.6-54.2
By age 8 years 92.6 80.9-104.3 57.1 55.5-58.6
Hence, by accumulating claims from birth and consulting Table 8.10, it becomes clear to which group the child belongs. This could be useful in assessing the child’s risk of surgery.
265 DISCUSSION
Substantial differences have been found between children who had and did not have ENT surgery in two methods of analysis. In the first crude analysis where total claims over the eight study years were compared, children who had surgery were found to have made almost twice as many claims for medical services as those who did not have surgery. The surgery group claimed for approximately 50% more GP consultations and almost three times the number of specialist consultations than did the non-surgery group. Their higher level of utilisation persisted throughout every type of medical service examined. Compared with 58% of the non-surgery group who claimed for at least one diagnostic test, almost all (92%) children who had ENT surgery made such a claim, with their respective percentages for the subgroup X-rays being 46% and 68%. Pathology claims were made by 91% of the children who had ENT surgery compared with 66% of the non-ENT group, with 72% of the ENT group compared with 40% of the non-ENT group making four or more such claims during the eight years. A difference was found even in optometry, where 41% of these children claimed at least once for optometry compared with 29% of the non-ENT group.
In the second multiple linear regression analysis the age-specific use of services of the groups were compared, including in the comparison only the pre-surgery months for the children in the surgery group. This analysis showed conclusive differences between the groups, with the surgery group making higher than average claims for services in every month of age from birth until eight years. Despite the claims of these children diminishing over time at a greater rate than that of the non-surgery group, claims never converged: by eight years of age their average monthly utilisation of services remained at a higher level.
266
Hence, the health service utilisation characteristics of these children prior to surgery were found not to be the same as the characteristics of the group who did not have surgery. This supports a hypothesis that higher utilisation of ENT-related services is to be expected in the period prior to treatment of the ENT condition by surgery. However, some of the findings regarding total claims over the whole 8 years give rise to speculation that some excess services may not be ENT-related, such as the fact that these children used a significantly higher percentage of optometry services, which are rarely used in response to a specific illness. If not ENT-related, another possible explanation could be that, because these children are known to have had privately funded surgery and hence belong to a higher income group, their parents could afford to use medical services more frequently than others. However, income ought not to be a factor in the use of primary health services in Australia. The
Medicare system aims, although with less than total success, to provide equitable accessibility to such services, regardless of income. Yet, as seen in Tables 6.10 – 6.12, rural children used fewer total services, GP and specialist services than children residing in metropolitan areas, possibly due to distance and supply of services, and, since proportionally fewer rural children were found in the surgery group (Table 6.13) and hence more in the non-surgery group, their lower use of services would have contributed to the differences found. However, since rural children were relatively few in number, this factor could not account for the differences in utilisation. Again, if the excess is not ENT-related, another explanation might be that the parents of these children have a lower threshold for medical intervention or heightened concerns regarding their children’s general health. These possible explanations of the findings will be more fully explored in the concluding chapter.
267 In the following two chapters (Chapters 9 and 10), the health service claims of children who had myringotomy or tonsillectomy will be further scrutinized, in order to estimate the degree of compliance with guideline recommendations.
268 Chapter 9 GUIDELINE COMPLIANCE AMONG COHORT CHILDREN WHO HAD ENT SURGERY: INTRODUCTION & METHODS
This chapter describes the potential afforded by health services claims for examination of the
extent of compliance with specific guideline recommendations. It outlines methods of
identifying compliance with key recommendations among the cohort children who had ENT
surgery.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline surgery Total cohort Subsequent compliance: rates: utilisation: utilisation: Results & Results & Results & Results & discussion discussion discussion discussion Chapter 13 Chapter 4 Chapter 7 Effect of ENT Economic guidelines on cohort impact: rates utilisation: Results & Results & discussion discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
269 INTRODUCTION
In the epidemiological section of the current study, variation, both geographical and secular, in the performance of ENT surgery among NSW children has been established. As described in Chapter 1, surgical guidelines were disseminated in NSW for tonsillectomy and adenoidectomy in 198214 (Appendix 9) and for myringotomy in 199313 (Appendix 10). The nature of the HIC data allowed compliance with some specific guideline recommendations regarding treatment or tests prior to ENT surgery to be verified.
There are two recommendations in the Guidelines on the Management of Middle Ear
Disease13 that concern treatment prior to surgery. It was possible to use the HIC data to test whether these recommendations had been followed for the children who had had myringotomy.
In these Guidelines, the protocol recommended for the management of otitis media with effusion was as follows.
270
Otitis media with effusion
Assess *duration *degree of hearing loss and other symptoms *complications
Complications No complications Amoxicillin 10-28 day course 50 mg/kg per day or alternative antimicrobial agent
No resolution Resolution
Review *significant hearing loss *duration > 3 months Options *complications *antibiotic *prednisolone and antibiotic (possible role in selected cases) *tympanostomy tube insertion *adenoidectomy (possible role in selected Yes No cases) *watch and wait Consult ENT surgeon *Monitor progress *Possible role for autoinflation
No resolution Resolution
Referring to the above protocol, it can be seen that the first recommendation that might be verifiable in these HIC data concerns antimicrobial treatment. The Guidelines suggest that
271 medical treatment could be considered to have failed after three months of attempts to treat otitis media with effusion with antimicrobial agents. Hence the number of GP consultations claimed by these children prior to myringotomy could be considered an indicator of whether medical treatment was attempted before proceeding to surgery. A period of six months prior to surgery was considered sufficient time for arrangements to be made for surgery if found necessary. A GP visit in this context can be considered a proxy for treatment with antimicrobial agents. This is a conservative approach, as not all GP visits would have been for this purpose.
The second recommendation concerns audiology assessment. Prior to treating otitis media with effusion with surgery, the Guidelines recommend assessment of the degree and duration of hearing loss. Where no complications exist, the Guidelines then recommend treatment with an antimicrobial agent, followed, in the case of no resolution of the problem, by a further audiology assessment prior to the decision to conduct surgery.
With regard to tonsillectomy, according to the 1982 guidelines14 described in Chapter 1, one indication for surgery which can be tested in the HIC data is airway obstruction, signalled by loud snoring during sleep with intermittent obstructive apnoeic episode (OSAS). The clinical practice guideline of the American Academy of Pediatrics for the diagnosis and Management of Childhood Obstructive Sleep Apnea Syndrome16 recommends polysomnography for the diagnosis of OSAS . This is in preference to the common method of history taking and physical examination, which do not reliably distinguish between OSAS and primary snoring, nor does size of the tonsils and adenoids alone indicate the presence of OSAS. The guideline recommends adenotonsillectomy as the first line of treatment of reliably diagnosed OSAS. 272 METHODS
Study design
The MBS claims histories of those cohort children who received myringotomy were examined for evidence of compliance with 1993 guidelines13 (Appendix 10).
The MBS claims histories of those cohort children who received tonsillectomy were examined for evidence of compliance with 1982 guidelines14 (Appendix 9).
Criteria for identification of compliance
Myringotomy
The date of the first myringotomy recorded for each child who had this surgery was identified and the child's records during the six months preceding this date examined.
To comply with guideline recommendations regarding antimicrobial treatment a minimum of
3 physician visits would be required during the six months prior to surgery. Accordingly, records for each child who had myringotomy were examined and counts made of the number of GP and specialist consultations claimed during this period.
To determine whether hearing status had been assessed prior to surgery, each child’s records were searched for evidence that a hearing related claim had been paid by Medicare during the six months preceding surgery.
The MBS item numbers designating the relevant diagnostic procedures and investigations were:
273 MBS item number MBS description 11303 ELECTROCOCHLEOGRAPHY, extratympanic method, 1 or both ears 11306 Non-determinate AUDIOMETRY 11309 AUDIOGRAM, air conduction 11312 AUDIOGRAM, air and bone conduction or air conduction and speech discrimination 11315 AUDIOGRAM, air and bone conduction and speech 11318 AUDIOGRAM, air and bone conduction and speech, with other Cochlear tests 11324 IMPEDANCE AUDIOGRAM involving tympanometry and measurement of static compliance and acoustic reflex performed by, or on behalf of, a specialist in the practice of his or her specialty, where the patient is referred by a medical practitioner - not being a service to which item 11309, 11312, 11315 or 11318 applies 11327 IMPEDANCE AUDIOGRAM involving tympanometry and measurement of static compliance and acoustic reflex performed by, or on behalf of, a specialist in the practice of his or her specialty, where the patient is referred by a medical practitioner - being a service to which item 11309, 11312, 11315 or 11318 applies 11330 IMPEDANCE AUDIOGRAM where the patient is not referred by a medical practitioner - 1 examination in any 4 week period
The following descriptions explain the meaning of the terms used in the above table and the tests to which they refer.
AUDIOMETRY is a method of testing and measuring the hearing sensitivity of an ear to sound waves on different frequencies (pitch) and loudness. It is the first step in testing hearing. The person signals when he hears a tone. For each pitch, the test identifies the quietest tone the person can hear in each ear.
An AUDIOGRAM is a chart showing the results of the hearing ability test as recorded by an instrument called an audiometer. The results are presented in comparison to what is considered normal hearing. Loudness is measured in decibels (dB), which are on a
274 logarithmic scale, so that an increase of 2dB doubles the sound intensity. The following table gives examples of the decibel values of everyday sounds334.
Jet take-off (from 60m) 130 dB Shotgun blast 100 dB Car horn at 6m 90 dB Inside sports car at 50 mph 80 dB Loud thunder 70 dB Normal conversation 60 dB Typical room 40 dB Soft whisper at 1.5m 30 dB Open country 10 dB
From the above chart it can be seen that a hearing loss of 30 dB means that a normal conversation sounds like a soft whisper. Clinically, a persistent bilateral hearing impairment of 25-30 dB due to OME is sometimes thought serious enough to justify consideration of surgery12.
AIR CONDUCTION is the conduction of sound to the inner ear through the air and tympanum.
BONE CONDUCTION is the conduction of sound to the inner ear through the bones of the skull.
SPEECH THRESHOLD AUDIOMETRY measures how loudly words have to be spoken to be understood. In this test a person listens to a series of two-syllable equally accented words at different volumes. The volume at which the person can correctly repeat half of the words is recorded.
TYMPANOMETRY tests how well sound can pass through the eardrum and middle ear. It measures indirectly the compliance (mobility) and impedance of the tympanic membrane and ossicles of the middle ear. It is commonly used in children, since it does not require their active participation335. In this procedure the external acoustic meatus is subjected to positive, normal and negative air pressure and the resultant sound energy flow monitored336. A device containing a microphone and a sound source is placed in the ear canal, and sound waves are 275 bounced off the eardrum as the device varies the pressure in the ear canal. Abnormal tympanometry suggests a conductive type of hearing loss.
ELECTROCOCHLEOGRAPHY measures the activity of the cochlea and the auditory nerve by means of an electrode placed on, or through the eardrum. This test is used to measure hearing in people who cannot respond voluntarily to sound, such as infants with profound hearing loss.
276 Tonsillectomy
OSAS is only reliably diagnosed by polysomnography. The indication for tonsillectomy among an unknown number of children might have been OSAS. Hence records of each child who had tonsillectomy were searched for evidence that a claim for polysomnography had been paid by Medicare prior to surgery.
The MBS item number designating polysomnography was:
MBS item MBS description number 12203 OVERNIGHT INVESTIGATION FOR SLEEP APNOEA FOR A PERIOD OF AT LEAST 8 HOURS DURATION WHERE (a) continuous monitoring of oxygen saturation and breathing using a multi-channel polygraph, and recordings of EEG, EOG, submental EMG, anterior tibial EMG, respiratory movement, airflow, oxygen saturation and ECG are performed; (b) a technician is in continuous attendance under the supervision of a consultant physician in thoracic medicine, or a specialist where the investigation is performed in the sleep laboratory of a recognized hospital; (c) the patient is referred by a medical practitioner; (d) The necessity for the investigation is determined by the supervising medical practitioner prior to the investigation; (e) Polygraphic records are analysed (for assessment of sleep stage, arousals, respiratory events and assessment of clinically significant alterations in heart rate and limb movement) with manual scoring, or manual correction of computerized scoring in epochs of not more than 1 minute, and stored for interpretation and preparation of report; and (f) Interpretation and report are provided by the supervising medical practitioner based on reviewing the direct original recording of polygraphic data from the patient
POLYSOMNOGRAPHY (sleep study) is a diagnostic technique which quantifies the ventilatory and sleep abnormalities associated with sleep-disordered breathing16. It requires appropriate equipment and trained staff to observe sleep patterns overnight. It can distinguish
OSAS from primary snoring and can determine objectively the severity of OSAS. 277 Chapter 10 GUIDELINE COMPLIANCE AMONG CHILDREN WHO HAD ENT SURGERY: RESULTS & DISCUSSION
This chapter presents evidence regarding guideline compliance as reflected in claims for
health services. The first set of results refers to compliance among cohort children who had
myringotomy with recommendations of the NSW guidelines on the management of middle ear
disease. The second refers to compliance with a recommendation of the American Academy of
Pediatrics regarding polysomnography among those children who had tonsillectomy.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort Results & guidelines on utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
278 RESULTS
Compliance with specific myringotomy guideline recommendations
Antimicrobial treatment
Prior to myringotomy, the 1993 guidelines recommended treatment with antimicrobial agents for at least 3 months. Table 10.1 shows the number of GP visits claimed per child in the six months prior to myringotomy.
Table 10.1 Number of GP visits per child in 6 months prior to myringotomy Number of GP visits Number of % of children Cumulative % children 0 5 2.2 2.2 1 9 3.9 6.0 2 17 7.3 13.4 3 19 8.2 21.6 4 18 7.8 29.3 5 28 12.1 41.4 6-7 37 15.9 57.3 8-9 35 15.1 72.4 10-11 25 10.8 83.2 12-13 14 6.0 89.2 14+ 25 10.8 100.0 All children 232 100.0
Most of the children who had myringotomy claimed for a number of GP visits during the six months preceding surgery, five being the number of visits most frequently claimed.
However, 31 of these children (13.4%) claimed fewer than three GP visits, with therefore no opportunity for the recommended amount of prior antimicrobial treatment to have been attempted. These children might, however, have received this treatment from a specialist.
Table 10.2 shows the number of specialist consultations claimed for by each child during the six months prior to their first myringotomy.
279 Table 10.2 Number of specialist consultations per child in 6 months prior to myringotomy Number of specialist Number of % of children Cumulative % consultations children 0 9 3.9 3.9 1 106 45.7 49.6 2 78 33.6 83.2 3 17 7.3 90.5 4 12 5.2 95.7 5 3 1.3 97.0 6 2 0.9 97.8 7 1 0.4 98.3 8 3 1.3 99.6 12 1 0.4 100.0 All children 232
Table 10.2 shows that 96.1% of these children consulted a specialist at least once during the six months preceding surgery, 50.4% had two or more consultations and 16.8% three or more.
Hence even those children who had fewer than three GP visits could have received antibiotics from a specialist during this pre-surgery period.
An analysis of the number of GP and/or specialist claims showed that only 1 child made no claim for either type of physician visit, 1 child made 1 claim and 8 children made 2 claims during the period, with the remainder 222 children making at least 3 claims and the median being 8 claims. Therefore 96% of children had the opportunity of being prescribed antibiotics on at least 3 occasions during the 6 months preceding myringotomy, although it is unknown whether all these children did receive such a prescription.
Audiology assessment
A total of 245 claims for audiology were made by this subgroup of children. Details of the number of claims made under each MBS audiology item number are shown in Table 10.3.
280 Table 10.3 Total audiology claims made by children in six months prior to myringotomy by MBS item number
MBS item MBS description Number % number of claims 11303 ELECTROCOCHLEOGRAPHY, extratympanic method, 2 0.8 1 or both ears 11306 Non-determinate AUDIOMETRY 2 0.8 11309 AUDIOGRAM, air conduction 32 13.1 11312 AUDIOGRAM, air and bone conduction or air 50 20.4 conduction and speech discrimination 11315 AUDIOGRAM, air and bone conduction and speech 4 1.6 11318 AUDIOGRAM, air and bone conduction and speech, 1 0.4 with other Cochlear tests 11324 IMPEDANCE AUDIOGRAM involving tympanometry 60 24.5 and measurement of static compliance and acoustic reflex performed by, or on behalf of, a specialist in the practice of his or her specialty, where the patient is referred by a medical practitioner - not being a service to which item 11309, 11312, 11315 or 11318 applies 11327 IMPEDANCE AUDIOGRAM involving tympanometry 73 29.8 and measurement of static compliance and acoustic reflex performed by, or on behalf of, a specialist in the practice of his or her specialty, where the patient is referred by a medical practitioner - being a service to which item 11309, 11312, 11315 or 11318 applies 11330 IMPEDANCE AUDIOGRAM where the patient is not 21 8.6 referred by a medical practitioner - 1 examination in any 4 week period All audiology 245 100.0 claims
Most (62.9%) assessments were impedance audiograms performed by specialists, while
35.5% were simple audiograms, with or without speech discrimination.
The above 245 audiology assessments were claimed by 127 (54.7%) of the 232 children who had myringotomy (Table 10.4).
281 Table 10.4 Number of audiology assessments per child during six months prior to myringotomy
Number of audiology Number of children % of children Cumulative % assessments per child 0 105 45.3 45.3 1 51 22.0 67.3 2 54 23.3 90.6 3 11 4.7 95.3 4 5 2.2 97.5 5 2 0.8 98.3 6 4 1.7 100.0 Total number of children who had myringotomy 232 100.0
While 54.7% of the children who had myringotomy claimed for at least one audiology assessment and 32.7% claimed for 2 assessments, almost half (45.3%) made no such claim during the six months prior to myringotomy. Among the 127 children who did claim, 60.3% had more than one assessment during this period.
However, most (65.9%) children who had myringotomy had an audiological assessment in the months following the procedure, including, surprisingly, 46 (43.8%) of the 105 children who did not have an assessment prior to surgery.
An examination of whether the children who had fewer than three physician visits in the six months prior to surgery were the same children who failed to claim for an audiology assessment revealed that there were only five such children. Each of these 5 children claimed for two attendances. Hence of the 9 children identified earlier as having had fewer than 3 consultations of either type, four did have an audiology assessment.
282 Table 10.5 examines whether the assessment of hearing prior to myringotomy differed by age of child.
Table 10.5 Audiology assessment during six months prior to myringotomy by age
Age of child Hearing assessed Hearing not assessed No. of children % of children No. of children % of children < 1 year 3 30.0 7 70.0 1 year 24 52.2 22 47.8 2 years 16 47.1 18 52.9 3 years 29 61.7 18 38.3 4 years 17 50.0 17 50.0 5 years 23 67.6 11 32.4 6 years 9 60.0 6 40.0 7 years 6 50.0 6 50.0 All children 127 54.7 105 45.3
Although in Table 10.5 the percentage of children whose hearing was tested prior to myringotomy appeared to vary by age, these apparent age differences were not statistically significant (chi-square = 7.193, d.f. =7, p=0.409).
Table 10.6 examines the percentage of children whose hearing was tested prior to myringotomy by their area of residence.
283 Table 10.6 Prior audiology assessment by area of residence Area of residence Number of children Number of % who had who had children who had audiology myringotomy audiology assessment assessment Western Sydney 23 16 69.6 South Western Sydney 22 15 68.2 Central Sydney 21 14 66.7 Wentworth 15 10 66.7 Mid North Coast 3 2 66.7 Far West 3 2 66.7 Central Coast 17 11 64.7 Hunter 11 7 63.6 South Eastern Sydney 18 10 55.6 Northern Sydney 36 18 50.0 Illawarra 20 10 50.0 Southern 10 5 50.0 Interstate 13 5 38.5 New England 8 2 25.0 Northern Rivers 2 0 0.0 Macquarie 1 0 0.0 Mid Western 4 0 0.0 Greater Murray 5 0 0.0 232 127 54.7
Among the inner and outer metropolitan Areas (marked in bold type), in only Northern
Sydney, Illawarra and South Eastern Sydney did fewer than 56% of children have assessments prior to myringotomy. Some rural Areas had very low percentages - however, these related to small numbers of children.
Omitting interstate and combining the Areas of residence into three broad groups, Inner metropolitan, Outer metropolitan and Rural, the following percentages of children whose hearing was tested prior to myringotomy in each of these broad groups were obtained (Table
10.7).
284 Table 10.7 Prior audiology assessment by broad area of residence Broad area of residence Number of children Number of % who had who had children who had audiology myringotomy audiology assessment assessment Inner metropolitan 98 58 59.2 Outer metropolitan 85 53 62.4 Rural 36 11 30.6 All NSW 219 122 55.7
Table 10.7 confirms that significantly fewer children living in rural areas had an audiology assessment during the six months prior to myringotomy (chi-square=11.231, d.f.=2, p<.005).
Evidence of guideline-sanctioned tonsillectomy indications
In the 1982 tonsillectomy and adenoidectomy guidelines14(Appendix 9), one of the criteria for tonsillectomy was airway obstruction – loud snoring during sleep with intermittent apnoeic episodes. Reliable diagnosis of sleep apnoea requires overnight observation using polysomnography 16 175 192 193. Examination of the MBS claims records of the 149 children who claimed for tonsillectomy revealed that only two of these children made a claim for polysomnography. Further, each of the two children made two claims for this investigation of
OSAS, and, for both children, the claims were made after, not before, tonsillectomy. One child made the first claim for polysomnography 209 days after tonsillectomy, and the second claim 801 days after that. The other child made the first claim 135 days after tonsillectomy and the second claim 473 days after the first.
285 DISCUSSION
The guidelines on the management of paediatric middle ear disease13 recommend that, in the case of OME, medical management in the form of a course of an appropriate antimicrobial agent should precede surgical intervention. This analysis has shown that almost all the cohort children who had myringotomy had several consultations prior to their surgery. It is unlikely that, in these visits leading up to surgery, antimicrobial treatment was not attempted. Hence the conclusion must be that this particular guideline recommendation was followed in most cases – 222 of the 232 children claimed for at least three GP or specialist attendances in the period prior to myringotomy, with 8 claiming for two attendances, one child claiming for one and only one child making no such claim. It is also possible that those who claimed for fewer than 3 attendances could have been prescribed the recommended number of treatments with antimicrobial agents at a single visit.
However, there does not appear to be the same degree of compliance with the guideline recommendation that there should be audiological assessment of children with OME whenever possible, particularly if surgical management is being considered. Almost half the cohort children who had myringotomy did not have their hearing assessed. Since less than one third of the children living in rural areas had an assessment, it might be thought that it was the presence of these children in the cohort which inflated the overall non-compliance percentage. The low rural percentage could be due to considerations of distance and supply, rather than non-compliance. However, even excluding these 36 rural children for whom the low percentage might be explainable, the percentage remains a sizeable 40% of metropolitan children who did not have any audiological assessment prior to surgery.
286 A major reason for myringotomy is to alleviate loss of hearing and its behavioural and developmental sequelae following unresolved OME. It would seem appropriate to assess the degree of hearing capacity prior to intervention. Although in the guideline protocol (see
Chapter 8 Methods) there is an emphasis on hearing assessment, in the accompanying text the surgical decision is held to depend upon a number of factors other than hearing loss, such as duration of the effusion, the presence of complications, such as pathological changes in the middle ear due to the effusion, and severity of symptoms. These accompanying guideline notes also state surgery to be appropriate “when the associated hearing loss is resulting in behavioural or learning difficulties”. This appears to suggest that the presence of such reported difficulties could be used to verify observed (but not clinically assessed) hearing loss. The guideline’s wording leaves much to the discretion of the physician (Appendix 7).
An evaluation of the acceptability of these guidelines among the NSW clinical community was carried out in 1996297. In this evaluation over 95% of all types of clinicians agreed with the management strategy of assessing the degree of hearing loss of children with OME. The majority of clinicians also agreed with the need for hearing monitoring (audiometry) and middle ear monitoring (incorrectly designated in the questionnaire as “tympanostomy” monitoring). Although the latter term was incorrect, in the context it was probably assumed by respondents to denote tympanometry; however, it is possible that its use may have influenced results. The degree of agreement with the strategy of hearing monitoring differed by type of clinician: 85.6% of paediatricians agreed it was beneficial, compared with 92.6% of audiologists, 96.7% of audiometrists, 80.7% of ENT specialists and 81.2% of GPs. The degree of agreement with the strategy of middle ear monitoring was 74.0% of paediatricians,
96.3% of audiologists, 97.8% of audiometrists, 64.2% of ENT specialists and 79.2% of GPs.
287 Hence it can be seen that the two groups of clinician, GPs and ENT specialists, whom children suffering from OME are most likely to consult, are those with the lowest levels of agreement with the hearing and middle ear monitoring strategies recommended by the guidelines.
Regarding tonsillectomy, it is unknown what the indications for surgery among the cohort children were, and for how many, if any, the indication was sleep apnoea. Nevertheless, it was surprising to find that only two of the 149 children who had tonsillectomy had made a claim for polysomnography during the 8 study years, and that neither of these two children had had the investigation prior to surgery. Sleep apnoea has become an increasingly important indication for surgery. As noted in Chapter 1, in Italy the criteria for surgery among 97% of children under 3 years of age who had tonsillectomy were found to be obstructive sleep problems, history of snoring, eating and swallowing disorders229. Others also endorse OSAS as an indication for tonsillectomy196 208. It appears from the current analysis that, if sleep apnoea had been the indication for surgery for any of the cohort children, its diagnosis must have been made clinically, using history of snoring and physical examination, rather than using polysomnography. Yet the American Academy of Pediatrics recommends polysomnography rather than history and physical examination, which are held to be poor at predicting OSAS16. Further, the AAP guidelines for OSAS report that evidence has shown no relation between the size of the tonsils and adenoids and the presence of OSAS. Other expert opinion agrees with the AAP that the diagnosis of OSAS be made definitively, using polysomnography, rather than clinically176 192 194 230 231. However, polysomnography is an expensive and time-consuming investigation, requiring specialized equipment, considerable expertise and overnight observation to monitor and interpret results. It is a procedure that
288 may cause anxiety to both child and parent. These results show that in NSW, if sleep apnoea had been diagnosed among any of these cohort children as an indication for their tonsillectomy, it must have been diagnosed clinically.
In the next chapter (Chapter 11), the utilisation patterns of the cohort children who had ENT surgery are further examined to determine whether the performance of ENT surgery resulted in decreased subsequent health service utilisation.
289 Chapter 11 EFFECT OF ENT SURGERY ON HEALTH SERVICE UTILISATION: INTRODUCTION & METHODS
This chapter introduces a rationale for using claims for medical services as a measure of the
effectiveness of ENT surgery. If surgery is effective in alleviating health problems, there
should be a noticeable reduction in demand for medical services post-surgery among the
cohort children who had surgery. Methods of assessing whether this occurred, as well as
whether any possible effect differed by age of the child at time of surgery, are described.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort guidelines on Results & utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
290 INTRODUCTION
It was previously found (Chapter 8) that the cohort children who had ENT surgery used considerably more health services in the pre-surgery period than their peers who did not have surgery. It would be a reasonable expectation that, following ENT surgery aimed at resolving chronic conditions, the child’s subsequent use of health services should be reduced. There are a number of studies which report the views of carers (generally mothers) surveyed following their child’s surgery118 131 197 220 221 224 321. Invariably these studies reveal that the majority of parents reported that their child’s health, appetite, sleep patterns, attention and general well- being had improved.
By contrast with these subjective assessments of improvement, the current study tests objectively the hypothesis of improvement, with health service utilisation used as the operational definition of health problems. It is reasonable to assume that the use of health services reflects health status, although it is also possible that such utilisation may reflect parental attitudes and behaviour. Other factors which might affect use of health services, such as socioeconomic and geographical circumstances to which variation is often attributed, are controlled for by examining the same child before and after surgery.
Specifically in this part of the study, health service utilisation was used as a proxy for health status among those children who had the leading types of ENT surgery, tonsillectomy and myringotomy, and their patterns of claims for health services were examined to detect whether a reduction occurred following surgery.
291 METHODS
Study design
This study is a longitudinal case series with an intervention. Patterns of health service utilisation of those children who had tonsillectomy or myringotomy were compared before and after surgery, taking into account age of the child. Three groups for each type of surgery were then formed according to child’s age at time of surgery. Finally the utilisation pattern of each of these age-at-surgery groups was compared with that of the children who did not have surgery to verify whether the differences between surgery and non-surgery groups found in
Chapter 8 remained, regardless of age at time of surgery.
Data source
Using the same Medicare dataset, MBS claims records of only those cohort children who had
ENT surgery were examined.
Statistical analysis
Bivariate analysis
The effect of surgery on health service utilisation was measured for each child by comparing the total number of claims in the year before surgery with the total after, excluding the perisurgery period. In this part of the analysis, the perisurgery period was arbitrarily defined as being 35 days before to 35 days after surgery, including the day of surgery. This period was selected as to reasonably include MBS claims made for any tests, such as blood tests, that might be ordered by the surgeon prior to surgery, all claims related to the day of surgery, such as anaesthetist, assistant surgeon and pathology claims, and post-operative care during the following month. 292
These dates were unique to each child. Three totals were obtained for each child who had
ENT surgery. The first was the sum of all claims made during the year prior to the perisurgery period, the second total was the sum of claims during the perisurgery period and the third the sum in the year following the perisurgery period. Sets of averages of these individual totals were obtained for tonsillectomy, adenoidectomy and myringotomy in turn.
Multivariate analysis
In this part of the analysis, more complex outcome measures were devised to determine whether surgery had had any effect on service utilisation, while taking various factors into account. In this analysis only tonsillectomy and myringotomy were examined. This was because adenoidectomy is mainly performed in conjunction with one of the other procedures
(only 27 of the 359 children who had ENT surgery had adenoidectomy alone (Table 7.2) and hence cannot supply independently useful information. Using these Medicare data it was impossible to isolate children who had tonsillectomy alone, therefore it was decided to allocate all children to groups that were ‘mainly tonsillectomy’ or ‘mainly myringotomy’.
Hence children who claimed for MBS codes 41788 or 41789 (tonsillectomy or tonsillectomy with adenoidectomy) or MBS codes 41800 or 41801 (adenoidectomy) or more than one of these were allocated to the ‘mainly tonsillectomy’ group (127 children). Those who claimed for MBS code 41632 (myringotomy) as a single code or also claimed any of the preceding tonsillectomy or adenoidectomy codes were allocated to the ‘mainly myringotomy’ group
(232 children).
293 To measure the effect of surgery, this analysis was necessarily complex, as it had to take into account and adjust for the following known factors:
1. Diminished service utilisation with increasing age
2. Variation in age at which surgery was performed
3. Increased utilisation in the perisurgery period
In order to take account of all these factors, multiple linear regression analyses333 were performed in a similar manner to the regression analysis in Chapter 8, which, as seen in
Figure 8.1, provided a reasonable fit to the data. Counts of claims were made for each child for each month of the eight years. These counts were the dependent variables (CLAIMS).
The months were assigned numbers, from 1 to 96, which also represented the child's age in months (AGE). Month of surgery was flagged, as were each of the three months before and the two after. Preliminary analysis was performed to determine how many of these perisurgery months it was necessary to retain in the models. This analysis showed that only the two months preceding surgery (2MONTHS PRE and 1 MONTH PRE), the month during which surgery occurred (MONTH) and the first month after surgery (1 MONTH POST) needed to be retained in the regression model, since neither the third month preceding surgery nor the second month following surgery differed significantly (p<0.01) from the trend.
Finally, the study factor, a variable that distinguished between the entire periods before and after surgery, excluding the perisurgery period, was created. This outcome variable
(PERIOD) was given the value 0 for pre-surgery months and 1 for post-surgery months. An interaction term, between the outcome variable and month, (PERIOD*AGE) was created to show any difference in trend following surgery. The first two months of age were omitted
294 from the final analysis, as the large number of claims in these months acted as outliers and distorted the age trend. The full regression model used was:
CLAIMS = AGE + MONTH + 2 MONTHS PRE + 1 MONTH PRE + 1 MONTH POST +
PERIOD + PERIOD*AGE
Initial analysis revealed that the age at which the child had surgery affected the result. Hence, for each of the procedure groups, three separate analyses were performed according to the child’s age at time of surgery: at modal age for the procedure, above the mode and below the mode. With reference to the previously obtained distributions of age at time of surgery (Table
7.1), the following age groups were selected for these three sets of analyses:
For tonsillectomy: children aged less than 4 years, aged 4 years, and aged older than 4 years at time of surgery.
For myringotomy: children aged less than three years, aged three years, and aged over three years at time of surgery.
For each of these age-specific analyses, all terms were initially entered into the model, which was then reduced to retain only those terms that fulfilled the criterion of p<0.01.
Results of these analyses are presented in the following chapter.
295 Chapter 12 EFFECT OF ENT SURGERY ON HEALTH SERVICE UTILISATION: RESULTS & DISCUSSION
This chapter presents the results of comparing the pre-surgery health service utilisation of
children who had tonsillectomy or myringotomy with their utilisation following surgery. It
further presents the results of such a comparison by age of child at time of surgery, and the
results of comparing the utilisation profiles of all such groups with profiles of the children
who did not have ENT surgery.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort guidelines on Results & utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
296 RESULTS
Bivariate analyses
Total claims pre- and post-surgery
The mean number of claims per child during the year before surgery, the perisurgery period
(71 days in this analysis) and the year following surgery is shown in Table 12.1.
Table 12.1 Mean claims per child: perisurgery period, year before surgery and year after surgery
Type of ENT surgery Tonsillectomy Adenoidectomy Myringotomy No. of children 149 111 232 Mean claims: 8.5 9.6 9.0 perisurgery period Mean claims: pre- 14.8 16.2 15.8 surgery year Mean claims: post- 9.4 11.6 13.1 surgery year Pre-post surgery 5.4 (decrease) 4.6 (decrease) 2.7 (decrease) difference P (Level of significance 0.0001 0.0001 0.0001 of difference)
In Table 12.1 it can be seen that the average number of claims in the year following surgery was significantly lower than the number in the year preceding surgery for all three types of
ENT surgery. However, it is known (Table 6.1) that utilisation of health services by children diminishes with age. Hence the extent of the effect of age on the above results is unknown.
An examination of Table 12.1 also reveals that the average number of claims during the 10- week perisurgery period, which would include claims for the surgery itself, anaesthesia and
297 pathology, were remarkably similar regardless of type of ENT surgery (8.5, 9.6 and 9.0 claims for tonsillectomy, adenoidectomy and myringotomy respectively).
GP consultations pre- and post- surgery
Most MBS claims were for GP consultations (Table 6.5). Hence the data were divided and the analyses repeated for GP and non-GP claims. Table 12.2 presents the results for GP consultations only.
Table 12.2 Mean claims per child for GP consultations: perisurgery period, year before surgery and year following surgery
Type of ENT surgery Tonsillectomy Adenoidectomy Myringotomy No. of children 149 111 232 Mean GP consults: 2.1 2.3 2.6 perisurgery period Mean GP consults: pre- 10.6 11.4 11.8 surgery year Mean GP consults: post- 6.3 7.3 7.9 surgery year Pre-post surgery difference 4.3 (decrease) 4.0 (decrease) 3.9 (decrease) P (Level of significance of 0.0001 0.0001 0.0001 difference)
From Table 12.2 it can be seen that total GP consultations were significantly lower in the year after than in the year before surgery for all types of ENT surgery. However, as in the case of total claims, the effect of age on these results is unknown.
The average number of claims for GP consultations in the same perisurgery period was very similar for all types of ENT surgery (2.1, 2.3, 2.6 GP consultations for tonsillectomy,
298 adenoidectomy and myringotomy respectively) but far lower than the average total claims for this period found in Table 12.1.
Non-GP claims pre- and post- surgery
Table 12.3 presents the results for non-GP MBS claims (including specialist claims).
Table 12.3 Mean claims (excluding GP consultations) per child: perisurgery period, year before surgery and year following surgery
Type of ENT surgery Tonsillectomy Adenoidectomy Myringotomy No. of children 149 111 232 Mean non-GP claims: 6.4 7.4 6.4 perisurgery period Mean non-GP claims: pre- 4.2 4.8 4.0 surgery year Mean non-GP claims: post- 3.1 4.3 5.2 surgery year Difference in non-GP claims 1.1(decrease) 0.5(decrease) 1.1(increase) pre-post surgery P (Level of significance of 0.0203 0.3403 0.0097 difference)
In Table 12.3 it can be seen that the average number of non-GP claims in the year prior to surgery did not differ significantly from the average in the year after, in the case of tonsillectomy or adenoidectomy. However, in the case of myringotomy, there was a significant increase in average non-GP claims in the year following surgery.
The average number of non-GP claims during the perisurgery period was again similar for all types of ENT surgery (6.4 for both tonsillectomy and myringotomy and 7.4 for adenoidectomy).
299
Multivariate analyses
The multiple regression analyses showing the difference in the number of MBS claims made by each child following surgery took into account and adjusted for the following: diminished service utilisation with increasing age, variation in age at which surgery was performed and the effect of increased claims during the perisurgery period.
Claims before and after tonsillectomy
Final regression results for the 48 children aged less than four years (Table 7.1) at time of tonsillectomy are shown in Table 12.4.
Table 12.4 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy when aged less than four years
Factor Estimated claims Standard error P Claims in 3rd month of age 1.879610 0.104769 0.0001 Change in claims per month -0.022689 0.004747 0.0001 (trend) Change in level of claims post -0.430768 0.203897 0.0347 surgery Adjustment to trend in claims 0.014124 0.005366 0.0085 per month post surgery Extra claims in 2 months 0.925819 0.336804 0.0060 perisurgery before surgery period 1 month before 1.405030 0.338010 0.0001 surgery Month of 5.492937 0.339278 0.0001 tonsillectomy 1 month after -0.006113 0.340607 0.9857 surgery Adjusted R2=0.0834
300 The interpretation of Table 12.4 is as follows. Children aged less than four years at time of tonsillectomy had a relatively high initial level of claims (1.880 in their third month of age), which declined over time (by 0.023 claims per month). Following surgery there was an initial decrease of 0.431 in the level of claims. However, after this, claims decreased by a lesser amount per month than in the pre-surgery period, declining by 0.009 (-0.023+0.014) per month. Estimated perisurgery increases in claims (related directly to the tonsillectomy) were estimated at an extra 0.926 claims two months before surgery, 1.405 one month before surgery, 5.493 extra claims during the month of surgery and no significant increase in claims during the month following surgery.
Results for the 37 children aged four years at time of tonsillectomy are shown in Table 12.5.
Table 12.5 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy at four years of age
Factor Estimated claims Standard error P Claims in 3rd month of age 1.663074 0.086208 0.0001 Change in claims per month -0.011353 0.002861 0.0001 (trend) Change in level of claims post -0.042868 0.317249 0.8925 surgery Adjustment to trend in claims per -0.000975 0.004896 0.8422 month post surgery Extra claims in 2 months before 1.222419 0.317721 0.0001 perisurgery surgery period 1 month before 1.763184 0.318401 0.0001 surgery Month of 3.921596 0.319106 0.0001 tonsillectomy 1 month after -0.008227 0.319835 0.9795 surgery Adjusted R2=0.0940 301
Similarly, in Table 12.5 it is seen that children aged four years at the time of their tonsillectomy also had an initially high level of claims (1.663 in their third month of age), which then declined at a rate of 0.011 claims per month. Following tonsillectomy, there was no change in the level or trend of claims for these children. The perisurgery effect was as follows: there were respectively 1.281 and 1.824 extra claims during the second and first months immediately preceding surgery, an extra 3.984 claims during the month of surgery, and no extra claims during the month following surgery.
Table 12.6 shows the results for the 64 children aged five years or older at time of tonsillectomy.
Table 12.6 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had tonsillectomy when aged five years or older
Factor Estimated claims Standard error P Claims in 3rd month of age 1.259142 0.048241 0.0001 Change in claims per month -0.005748 0.001126 0.0001 (trend) Change in level of claims post 0.288721 0.427328 0.4993 surgery Adjustment to trend in claims per -0.005187 0.005191 0.3178 month post surgery Extra claims in 2 months before 0.676156 0.213637 0.0016 perisurgery surgery period 1 month before 1.536977 0.213848 0.0001 surgery Month of 5.455769 0.214066 0.0001 tonsillectomy 1 month after -0.065497 0.215703 0.7614 surgery Adjusted R2=0.1059
302
In Table 12.6 it is seen that children who were aged five years or older at time of tonsillectomy had a lower initial level of claims (1.259 in their third month of age) than children who had tonsillectomy at a younger age, and this level declined more slowly over time (by 0.006 claims per month). Once again there was no change in either the level of claims or trend in the period following tonsillectomy. There were 5.456 extra claims during the month of surgery and 0.676 and 1.537 in the two months immediately preceding it, with no statistically significant extra claims in the month following.
To illustrate these tonsillectomy results, estimated claims by month (trends) were calculated for each age-at-surgery group and combined in Figure 12.1.
Figure 12.1 Estimated number of claims per month for children who had tonsillectomy at under four years of age, at four years of age and at older than four years.
7
6
5
4
3 No. ofclaims 2
1
0 1 5 9 131721252933374145495357616569737781858993 Age (months)
<4 years 4 years 5 years+
303 In Figure 12.1, for the purpose of illustrating the perisurgery claims effect, exact age at surgery was assumed to be 42 months for the group aged less than four years, 54 months for those aged four years and 66 months for those aged over four years at time of tonsillectomy.
This perisurgery effect is shown at arbitrary points to illustrate the surge of claims during this period. However, these extra claims should be disregarded as they do not affect the trend. It can be seen that children who had tonsillectomy when relatively young (under 4 years) had a higher initial rate of service utilisation and a higher rate of decline than the older groups.
However, by the time of surgery, their higher claims level had already declined to that of the older groups, and following surgery their rate of decline also slowed to that of the older groups. The level and rate of decline of claims did not change following surgery for the groups aged 4 years or older at tonsillectomy.
In Table 12.7, the above differences in estimated claims per month by age at time of tonsillectomy are summarised.
Table 12.7 Estimated claims per month by age at tonsillectomy
Factor Age at time of tonsillectomy
Under 4 years 4 years 5 years and older
Claims in 3rd month of 1.879610 1.663074 1.259142 age Decline in claims per -0.022689 -0.011353 -0.005748 month pre-surgery Adjustment to claims in -0.430768 No adjustment No adjustment month post-surgery Decline in claims per -0.008565 -0.011353 -0.005748 month post-surgery
304 The comparison between the age-at-surgery groups in the amount of claims related to the surgery itself, the extra claims made during the perisurgery period, is shown in Table 12.8.
Table 12.8 Estimated extra claims during perisurgery period by age at tonsillectomy
Period Age at time of tonsillectomy
Under 4 years 4 years 5 years and older
2 months before surgery 0.925819 1.222419 0.676156 1 month before surgery 1.405030 1.763184 1.536977 Month of tonsillectomy 5.492937 3.921596 5.455769 1 month after surgery 0.0 0.0 0.0 Total perisurgery period 7.823786 6.907199 7.668902
It can be seen in Table 12.8 that, for tonsillectomy, total extra MBS claims made during the perisurgery period ranged from 6.9 for 4-year-olds to 7.8 for the youngest children.
Claims before and after myringotomy
The following tables show the results for children who had myringotomy. Table 12.9 shows the results of the regression analyses for the 90 children who were aged less than three years at the time of their first myringotomy.
305 Table 12.9 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy when aged under three years
Factor Estimated claims Standard error P Claims in 3rd month of age 1.811304 0.082799 0.0001 Change in claims per month -0.018797 0.005272 0.0004 (trend) Change in level of claims post 0.073637 0.106839 0.4907 surgery Adjustment to trend in claims 0.004299 0.005376 0.4240 per month post surgery Extra claims 2 months before 1.027827 0.198802 0.0001 in surgery perisurgery 1.977659 0.199932 0.0001 period 1 month before surgery Month of 5.088410 0.201193 0.0001 myringotomy 1 month after 0.601461 0.202583 0.0030 surgery 2 months after 0.240948 0.204100 0.2378 surgery Adjusted R2=0.1372
The initial level of claims of children who were aged under three years at the time of their first myringotomy was 1.811, after which their claims declined by 0.019 per month.
Following surgery neither their level of claims nor the rate of decline in the number of claims per month changed significantly.
Extra claims made during the perisurgery period by children who were aged under three years at the time of their first myringotomy were: 1.028 in the second month prior to surgery, 1.978 in the month prior, 5.088 extra claims during the month of surgery and 0.601 extra claims during the month immediately following surgery, but no statistically significant extra claims in the second month following surgery.
306
Table 12.10 shows regression results for the 47 children who were aged three years at the time of their first myringotomy.
Table 12.10 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy at three years of age
Factor Estimated claims Standard error P Claims in 3rd month of age 0.833627 0.078973 0.0001 Change in claims per month 0.012371 0.003259 0.0001 (trend) Change in level of claims post 0.872648 0.169769 0.0001 surgery Adjustment to trend in claims -0.023200 0.003866 0.0001 per month post surgery Extra 2 months before 0.402850 0.235476 0.0872 claims in surgery perisurgery 0.781783 0.236361 0.0009 period 1 month before surgery Month of 4.682455 0.237287 0.0001 myringotomy 1 month after -0.264699 0.238255 0.2666 surgery 2 months after -0.211853 0.239263 0.3760 surgery R2=0.1174
Children aged three years at the time of their first myringotomy had a lower initial level of claims (0.834) than those who were younger at this time. By contrast with the younger children, the claims of these children increased by 0.012 per month until surgery. Following surgery, their level of claims increased initially by 0.863, but after this claims decreased at the rate of 0.011 (0.012371 - 0.0232) claims per month, by contrast with their pre-surgery trend of monthly increases of 0.012 claims. That is, for this group of children, surgery did produce a marked effect on their claims.
307 Extra claims made by these children during the perisurgery period were: no statistically significant extra claims 2 months prior to surgery, an additional 0.793 claims in the month prior to surgery, 4.694 extra claims during the month of surgery and no extra claims in the two months following surgery.
Table 12.11 shows the regression results for the 95 children aged over three years at time of their first myringotomy.
Table 12.11 Estimated age-adjusted claims per month pre- and post-surgery, and claims during perisurgery period for children who had their first myringotomy at four years of age or older
Factor Estimated claims Standard error P Claims in 3rd month of age 1.035709 0.034542 0.0001 Change in claims per month -0.004605 0.00086689 0.0001 (trend) Change in level of claims in post 0.037430 0.199613 0.8513 surgery period Adjustment to trend in claims 0.000329 0.002578 0.8986 per month post surgery Extra 2 months before 0.827569 0.139861 0.0001 claims in surgery perisurgery 1.306921 0.140026 0.0001 period 1 month before surgery Month of surgery 5.271123 0.140196 0.0001 1 month after 0.255526 0.140371 0.0687 surgery 2 months after -0.002495 0.140551 0.9858 surgery R2=0.1439
The initial level of claims of children who had their first myringotomy at four years of age or older (1.036 claims in their third month of age) was lower than the youngest group but higher
308 than the group aged 3 years at surgery. Claims then declined by 0.004 claims per month until the month of surgery. Post-surgery, there was no statistically significant change in either the level of claims or their rate of decline.
Estimated extra claims during the perisurgery period for this group were: 0.828 and 1.307 in the second and first months prior to surgery respectively, 5.234 extra claims during the month of surgery, and no significant extra claims in the 2 months following surgery. Combining these myringotomy results, estimated claims by month were calculated for each age-at- surgery group and combined in Figure 12.2.
Figure 12.2 Estimated number of claims per month for children who had myringotomy at under three years of age, at three years of age and at four years or older.
7
6
5
4
3 No. ofclaims 2
1
0 1 5 9 131721252933374145495357616569737781858993 Age (months)
<3 years 3 years 4 years+
For the purpose of illustrating the perisurgery effect, exact age at surgery was arbitrarily assumed to be 24 months for the group aged less than three years, 42 months for those aged 309 three years and 60 months for those aged over three years at time of first myringotomy. Figure
12.2 shows that the children who had myringotomy when aged under three years appear to be a special group with a high rate of service utilisation from birth. Their utilisation declined sharply, reaching the level of the oldest group by approximately five years of age, and then falling below this level. Neither the level of claims of this group nor its rate of decline changed following myringotomy. By contrast, the children whose myringotomy took place at three years of age started with a lower level of claims than the preceding group. However, their claims increased until the time of surgery, after which they decreased, descending to the level of the oldest group by eight years of age. Among children of this age at surgery, myringotomy produced a definite effect. The group who had myringotomy at age four years or older had a lower initial level of service utilisation than the first (youngest at time of myringotomy) group. Although declining at a lesser rate, the level of claims among this group was lower than that of the group aged 3 years at surgery, and lower than the youngest group until approximately five years of age. Surgery had no effect on the level of claims of this group nor on its age-related rate of decline.
In Table 12.12, the above differences in estimated claims per month by age at time of first myringotomy are summarised.
310 Table 12.12 Estimated claims per month by age at first myringotomy
Factor Age at time of first myringotomy Under 3 years 3 years 4 years and older Claims in 3rd month of age 1.811304 0.833627 1.035709 Change in claims per month -0.018797 0.012371 -0.004605 pre-surgery Adjustment to claims in No adjustment 0.872648 No adjustment month post-surgery Decline in claims per month -0.018797 -0.010829 -0.004605 post-surgery
So different was the effect of surgery among the group who had myringotomy at 3 years of age from the other groups that a table highlighting their differences in the period preceding surgery up to age 3 years was prepared. During this pre-surgery period, these children departed markedly from the trend displayed by all other cohort children, that of decreasing claims with increasing age. Because estimated monthly claims were too small to make meaningful comparisons, these were aggregated into six-monthly totals. Table 12.13 compares these totals for each of the three myringotomy groups.
Table 12.13 Total estimated six-monthly claims in first three years by age at time of first myringotomy Age of child Total estimated claims
Myringotomy at < 3 yrs Myringotomy at 3 yrs Myringotomy at 4+ yrs
1-6 months 10.5 5.3 6.1
7-12 months 9.8 5.7 6.0
13-18 months 9.1 6.2 5.8
19-24 months 8.4 6.6 5.6
25-30 months 7.8 7.0 5.4
31-36 months 6.0 7.5 5.3
311 In Table 12.13 the pattern of increasing claims in the age ranges prior to surgery among the children who had myringotomy at 3 years of age can readily be seen and contrasted with the claims pattern of those who had surgery either earlier or later. This Table also highlights the much higher initial claims of the children who had myringotomy when aged less than 3 years.
In Table 12.14 the extra claims made during the perisurgery period from Tables 9-11 are summarized and age-at-first myringotomy groups compared. (There were no statistically significant extra claims for any group 2 months after surgery, so this row was omitted from the table.)
Table 12.14 Estimated extra claims during perisurgery period by age at first myringotomy
Period Age at time of first myringotomy
Under 3 years 3 years 3 years and older
2 months before surgery 1.027827 0.402850 0.827569 1 month before surgery 1.977659 0.781783 1.306921 Month of myringotomy 5.088410 4.682455 5.271123 1 month after surgery 0.601461 0.0 0.0 Total perisurgery period 8.695357 5.867088 7.405613
It can be seen in Table 12.14 that, for myringotomy, the youngest children made the most extra MBS claims during the perisurgery period and children aged 3 years the fewest.
Comparison of age-specific results with children who had no ENT surgery
It has been seen that for most age-at-tonsillectomy or myringotomy subgroups no change in monthly claims was found following surgery. There were two exceptions. These were the 312 children who had myringotomy at 3 years of age, whose monthly claims increased until surgery and then declined, but not below the level of the other myringotomy groups, and the children who had tonsillectomy at age <4 years, whose monthly claims, initially at a far higher level, became comparable with the older groups following surgery. Hence, even in these subgroups, surgery did not lead to eventual convergence with the claims level of children who did not have ENT surgery.
It has already been shown (Figure 8.1) that, for the ENT surgery group as a whole, no such convergence took place. However, it was conceivable that the discrepancy found between the surgery and non-surgery groups might be due to the markedly higher levels of claims of children who were relatively young at the time of surgery. Accordingly a further analysis was undertaken, separating the two younger age-at-surgery groups. This was a comprehensive analysis with the following subgroups: children who did not have surgery, those who had myringotomy at age under 3, those who had myringotomy at age 3 or older, those who had tonsillectomy at age under 4, and those who had tonsillectomy at age 4 or older. (The few who had adenoidectomy only were not included in this model.) The results of this regression analysis, which includes the extra perisurgery claims for each ENT procedure, including adenoidectomy, are shown in Table 12.15.
313 Table 12.15 Trend in claims over 8 years: children who did not have ENT surgery compared with those who had tonsillectomy or myringotomy at two ages: when very young for the type of surgery or not
Factor Coefficient Standard P error Claims in 3rd Children who did not have ENT surgery 0.874920 0.003424 0.0001 month of age Adjustment to initial At < 3 years 1.013912 0.028763 0.0001 claims level: children 0.313446 0.022082 0.0001 who had myringotomy At 3 years+ Adjustment to initial At < 4 years 0.719740 0.049849 0.0001 claims level: children At 4 years+ 0.504877 0.026619 0.0001 who had tonsillectomy Change in Children who did not have ENT surgery -0.005782 0.000061 0.0001 claims per -0.009008 0.000512 0.0001 month Trend adjustment: At < 3 years children who had (trend) -0.000073 0.000396 0.8528 myringotomy At 3 years+ Trend adjustment: At < 4 years -0.005138 0.000891 0.0001 children who had -0.002710 0.000478 0.0001 tonsillectomy At 4 years+ Extra claims Tonsillectomy 2 months prior 0.803790 0.106599 0.0001 in 1 month prior 1.386917 0.106606 0.0001 perisurgery period Month of 4.496225 0.106615 0.0001 surgery Adenoidectomy 2 months prior 0.595428 0.134228 0.0001 1 month prior 1.062356 0.134228 0.0001 Month of 4.122685 0.134228 0.0001 surgery Myringotomy 2 months prior 0.528993 0.094516 0.0001 1 month prior 0.957761 0.094508 0.0001 Month of 3.303744 0.094502 0.0001 surgery 1 month post 0.270994 0.084441 0.0013 R2 = 0.0358
Table 12.15 shows that, even when comparing each different age-at-surgery group with the
children who did not have surgery, claims for the latter began at a lower level in their 3rd
month of age, and, although the level of claims of each of the surgery subgroups (except the
group who had myringotomy at age 3 years or older) declined at a greater rate than that of the 314 non-surgery group, when the above results were evaluated no convergence between the surgery and non-surgery groups was found (Figure 12.3).
Figure 12.3 Level of claims by month of age: children who had myringotomy or tonsillectomy compared with those who did not have ENT surgery
2 1.8 1.6 1.4 1.2 1 0.8 0.6 Number of claims 0.4 0.2 0 1 5 9 131721252933374145495357616569737781858993 Age (months)
No ENT surgery My ringotomy <3y rs Myringotomy 3yrs+ Tonsillectomy <4yrs Tonsillectomy 4yrs+
Figure 12.3 shows clearly that, throughout the whole study period, from birth until the age of
8 years, no age-specific tonsillectomy or myringotomy group reached the lower level of claims of children who did not have ENT surgery.
The above results could be used as a potential simple test for the risk of tonsillectomy and myringotomy in a similar way to that calculated for non-specific ENT surgery in Tables 8.9 and 8.10. From the regression results in Table 12.15, again excluding additional claims during the perisurgery periods, estimated monthly totals and their 99% confidence intervals
315 were calculated. Total annual estimated claims were obtained by summing these individual monthly estimated totals. Results are shown in Table 12.16.
Table 12.16 Age-specific claims: no surgery compared with surgery at younger and older than modal age Number of estimated claims (99% C.I.)
Age of Children who had Children who had Children who child tonsillectomy myringotomy did not have At age <4 At age 4+ At age <3 At age 3+ ENT surgery years years years years 1st year 18.3 (16.5,20.1) 15.9 (14.9,16.9) 21.5 (20.4,22.6) 13.8 (13.3,14.2) 10.0 (9.9,10.2)
2nd year 16.7 (14.5,18.9) 14.7 (13.4,15.9) 19.4 (18.1,20.7) 12.9 (12.5,13.4) 9.2 (9.1,9.4)
3rd year 15.1 (12.6,17.7) 13.4 (12.0,14.9) 17.3 (15.7,18.8) 12.1 (11.6,12.6) 8.4 (8.2,8.5)
4th year 13.6 (10.7,16.5) 12.2 (10.6,13.9) n.a. 11.3 (10.7,11.8) 7.6 (7.4,7.7)
5th year n.a.(had surgery) 11.0 (9.2,12.8) n.a. 10.4 (9.9,11.0) 6.7 (6.5,6.9)
6th year n.a. 9.8 (7.8,11.8) n.a. 9.6 (9.0,10.2) 5.9 (5.7,6.1)
7th year n.a. 8.6 (6.3,10.8) n.a. 8.8 (8.2,9.4) 5.1 (4.8,5.3)
8th year n.a. 7.3 (4.9,9.8) n.a. 7.9 (7.3,8.6) 4.2 (3.9,4.5)
It can be seen in Table 12.16 that at no age did any of the upper confidence limits of claims of children who did not have surgery overlap any of the bounds of the surgery groups. Hence, given observed claims, this Table could be used as a guide regarding the expectation of future surgery.
To facilitate the comparison of total claims from birth to any specified age, the above annual totals were accumulated (Table 12.17).
316 Table 12.17 Estimated cumulative claims by specified ages: surgery and non-surgery groups Age of child Cumulative estimated claims
Children who had Children who had Children who tonsillectomy myringotomy did not have At age <4 At age 4+ At age <3 At age 3+ ENT surgery years years years years By age 1 year 18.3 15.9 21.5 13.8 10.0
By age 2 years 35.0 30.6 40.9 26.7 19.3
By age 3 years 50.1 44.0 58.1 38.8 27.6
By age 4 years 63.7 56.2 n.a. 50.1 35.2
By age 5 years n.a. 67.2 n.a. 60.5 41.9
By age 6 years n.a. 77.0 n.a. 70.1 47.8
By age 7 years n.a. 85.6 n.a. 78.9 52.9
By age 8 years n.a. 92.9 n.a. 86.8 57.1
Again, if the number of observed MBS claims from birth were counted, Table 12.17 could provide an assessment of the child’s risk of surgery.
317 DISCUSSION
The results from the current chapter show that the performance of tonsillectomy or myringotomy had no effect on these children’s subsequent level of health service utilisation.
There was no reduction in their pattern of claims, which remained higher at all ages than that of children who did not have surgery.
There was one exception. This exception was the subgroup of children who underwent myringotomy at 3 years of age. Among this group of 47 children (20.2% of the total who had myringotomy), having surgery reversed an upward trend in their use of health services. By contrast with other subgroups, their use of health services, despite beginning in their first month of life at a similar level to those who had myringotomy when over 3 years, increased with increasing age rather than decreasing. This trend continued until surgery. Following surgery, their level of claims declined to the same level as the children who were older at the time of myringotomy (but not to the level of the non-surgery children).
The age at which children have surgery has been shown to be associated with patterns of health service utilisation. Children who had surgery when younger than the most common age for the type of surgery (3 years for myringotomy, 4 years for tonsillectomy - Table 7.1) were differentiated from the other groups by their higher rates of utilisation from birth.
However, by 4 or 5 years of age, their levels of utilisation had declined to be similar to their peers who had surgery at the most common age or older.
In Chapter 8 it was shown that the children who had ENT surgery had higher levels of health service utilisation than those who did not. This analysis has further shown that the health
318 service utilisation level of all subgroups of children who had surgery, regardless of their age at surgery, was higher than children who did not have surgery. This was despite the age- related trends of all subgroups of children who had surgery showing a steeper decline than that of the non-surgery children. There was no convergence. The level of utilisation of health services by children who had tonsillectomy or myringotomy remained higher than that of those who did not have ENT surgery throughout the years of the study period. Given the strength of this relationship, look-up tables have been proposed to assess a child’s risk of future privately funded surgery based simply upon observed counts of claims for medical care, independent of possible reasons underlying such counts.
319 Chapter 13 TOTAL COST OF ENT SURGERY
In this chapter, the total economic impact of ENT surgery on the Medicare system is
estimated. This includes all perisurgery costs as well as the extra claims shown in previous
chapters to have been made between birth and eight years of age by the children who had this
surgery.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort Results & guidelines on utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
320 INTRODUCTION
Concern over variation in elective surgical procedures is often motivated by the economic effect of some possibly unnecessary surgery and concern that there should be cost-effective use of scarce resources130. Such concern usually focusses on the hospital surgical episode.
While recognising the hospital costs surrounding ENT surgery, the current study has identified additional substantial non-hospital costs to the health system.
Substantial differences in health service utilisation between children who had ENT surgery and those who did not were reported in Chapter 8. In total over the eight years, children who had this surgery made almost twice as many claims for medical services, with about 50% more claims for GP consultations and almost three times as many specialist consultations.
These excess claims did not result from the surgical episode alone, but persisted throughout the period studied, from birth to 8 years of age. Following surgery, there was no diminution in the rate of claims (Chapter 12). These extra claims translate into additional costs to
Medicare, which has implications for the entire Australian health system.
In the current chapter costs to Medicare, which are in excess of costs of children who did not have ENT surgery, are estimated. The first component of this estimate is the cost to Medicare of the surgery itself. This component relates to the surgical episode, which includes the cost of surgery as well as its accompanying costs, such as anaesthesia and pathology, and the extra costs incurred during the months immediately prior to and following surgery, which form part of the lead up to surgery and aftercare. Despite being largely privately funded, all these perisurgery claims include a cost component payable by Medicare. The second component of
321 additional cost to Medicare is the amount of medical services claimed for throughout the study period by children who had surgery in excess of the amount claimed by children who did not have surgery. This study has found this excess use of services to be ongoing throughout the period studied, from the children’s birth until eight years of age.
To sum up, children who have ENT surgery have been found to be high users of medical services. The question addressed in this chapter is: how much more cost do they generate to
Medicare than the rest of the population? In this analysis, the economic implications of this particular child health issue both inside and outside the hospital setting, the most usual focus of consideration, are estimated.
322 METHODS
Definition of terms
Excess In the current economic analysis, the term ‘excess’ denotes the amount by
which the number of claims made by children who had ENT surgery is higher
than that of children who did not have surgery. No judgment of the level of
claims is intended.
Study design
This study used regression estimates to quantify the amount by which claims of children who had ENT surgery were in excess of children who did not. Exact amount and type of medical services claimed for during the perisurgery period by the children who had ENT surgery were derived. Both amounts were then applied to Medicare reimbursements as shown in the MBS and summed to obtain total cost estimates.
Data source and details
Perisurgery costs
From the full HIC dataset of cohort children’s Medicare records described in Chapter 5, a datafile containing records of only those children who had ENT surgery was created. From this, records of children who had tonsillectomy or myringotomy were re-examined to obtain details of claims made during the perisurgery period. (A separate analysis of perisurgery claims of children who had adenoidectomy was not undertaken since only 27 children had this procedure alone. Costs for this subgroup were later assumed to be identical to costs for the tonsillectomy group.) The perisurgery period, which included the date of the surgical episode itself as well as pre- and post-surgery, was defined as follows:
323 • For myringotomy, from 60 days before until 60 days after the date of surgery (4
months in total, since this was the perisurgery period identified by the regression
analyses in Table 12.15 as having above average claims)
• For tonsillectomy, 60 days prior to 30 days after (3 months in total, since the
regression analysis (Table 12.15) had shown no post-operative effect on claims after 1
month for tonsillectomy).
As the date of surgery differed for each individual child, each child had a unique perisurgery period. These perisurgery periods do not precisely coincide with those used in the regression analyses, since the latter used month rather than day as the base.
Separate analyses were made for tonsillectomy and myringotomy with or without any of the other two procedures. For children who had myringotomy, only the first myringotomy was analysed.
Frequency distributions of all Medical Benefit Scheme (MBS) item numbers falling within the perisurgery period were obtained. After examination of these frequency distributions, summary totals were calculated for the following relevant claim groups (selected MBS
Categories and Groups).
• GP attendances (MBS Groups A1 and A2)
• Specialist attendances (MBS Groups A3 and A4)
• Diagnostic procedures and investigations (MBS Category 2)
• Anaesthesia (MBS Group T6)
• Surgical Operations (MBS Group T8)
• X-rays (MBS Group I3)
• Pathology (MBS Category 6)
324 Within each of these groups the most prevalent item numbers were determined. The amount of compensation paid by Medicare corresponding to these items was determined with reference to the Medicare Benefits Schedule book, 1 November 1997, a date falling within the study period325. Items obviously referring to inhospital care received the amount equivalent to 75% of the scheduled fee, while the rest received amounts equivalent to 85% of the scheduled fee, in accordance with MBS instructions. These amounts were applied to the frequencies of the most prevalent MBS items, and the least costly amount of the group applied to the remaining items.
Perisurgery costs obtained in this way were then applied to all children who had ENT surgery.
The cost assigned to those who had a combination of tonsillectomy and myringotomy was the total myringotomy perisurgery cost plus the cost of the tonsillectomy procedure (assumed to be the most frequent item number claimed, 41789, the inhospital benefit for which amounted to 75% of the scheduled fee or $165.60). Similarly children who had myringotomy and adenoidectomy were assigned the total myringotomy perisurgery cost plus the cost of the adenoidectomy procedure ($91.30 for MBS item number 41801). Children who had adenoidectomy alone were assigned the tonsillectomy perisurgery costs, adjusted for the less costly adenoidectomy procedure (i.e., minus the cost of the tonsillectomy procedure plus the cost of the adenoidectomy procedure).
Excess costs from birth to eight years
To determine the cost of the excess of claims found to have been incurred between birth and eight years of age by these children when compared with children who did not have surgery, a
325 further multiple regression analysis was performed to cover all children who had ENT surgery, rather than the subgroups whose results were reported in the previous chapter.
A new data file was created for this multiple linear regression analysis containing one record for each child for each study month – 598,944 records in all. Each record contained a dummy variable (ENT) identifying whether the child had claimed for any type of ENT surgery at least once during the 8 year period, with value 1 and value 0 otherwise. Each record contained the month number, from 1 to 96 - these also represented the child's age in months (AGE).
Counts of claims for each child for each month were inserted into the records. These counts comprised the dependent variable (CLAIMS) in the linear regressions.
To eliminate the effect of excess claims during the perisurgery months on group differences, the following perisurgery dummy variables were created in each record. In line with what was already known from previous analyses about the perisurgery period, the two months before surgery, the month of surgery and, for myringotomy only, the month following surgery were flagged in each record. The record for each month then contained 10 perisurgery variables, 3 for tonsillectomy, 3 for adenoidectomy and 4 for myringotomy, with value 0 or 1 to denote whether the month was a perisurgery month. Hence these 10 variables all had value 0 for each of the 96 months for the 5880 children who did not have ENT surgery, and, for children who did have surgery, these variables had value 1 for only the relevant perisurgery months, which differed for each of these children.
The dummy variable ENT, indicating whether the child belonged to the surgery or non- surgery group, comprised the comparison variable. An interaction term between this variable 326 and age (ENT *AGE) was constructed to determine whether the trend in number of claims over time was the same for both groups.
The equation used in the full regression model was:
CLAIMS = AGE + ENT + ENT*AGE + 2mths pre-tonsillectomy + 1mth pre- tonsillectomy + tonsillectomy month + 2mths pre-adenoidectomy + 1mth pre-adenoidectomy + adenoidectomy month + 2mths pre- myringotomy + 1mth pre-myringotomy + myringotomy month + 1mth post-myringotomy
Results of this regression were used to evaluate estimated claims in each of the 96 months of the study for each group of children, and summed to obtain total estimated utilisation by each group over the whole period. For children who underwent surgery, 4 months of estimated claims were subtracted from the total to allow for the perisurgery period, which was separately analysed in the preceding section.
Difference in total claims between the two groups of children was then multiplied by the cost of an MBS service. Here a conservative approach was taken in that all claims were assumed to relate to GP consultations, the most prevalent type of claim, although such services are less costly than many other MBS items. This produced the second component of excess costs incurred by the children who underwent ENT surgery.
Estimate of total excess cost
The above two types of excess costs were summed for each child who had ENT surgery. To gain an estimate of the possible total excess cost to Medicare of all NSW children who have
ENT surgery, the proportion of such children in the cohort was applied to the NSW paediatric population and multiplied by the total excess cost estimated for each individual child.
327 Limitations
1. While not all claims during the perisurgery period would have related to the ENT
surgical episode, nevertheless they constituted part of the pattern of excess claims
made by these groups of children during this period and needed to be included.
2. The cost of every MBS item in the perisurgery analysis was not individually
determined. In each of the initial perisurgery distributions there were about 120
individual MBS items which were then grouped as described (Methods, Perisurgery
costs). It was not considered feasible to determine the cost of every one of these MBS
items and apply these multiple costs to the distribution. Hence costs were determined
for only the most frequent items and the less frequent items were assigned the same
cost as the lowest cost item in the group.
328 RESULTS
Perisurgery costs for children (N=232) who had myringotomy
During the entire episode surrounding the performance of myringotomy, 2720 MBS claims were made by the 232 children who had this procedure, alone or with another ENT procedure
(Table 13.1). Average benefits paid by Medicare amounted to $498.91 per child.
Table 13.1 Myringotomy perisurgery benefits paid by Medicare MBS item group MBS item Number Item benefit Total cost to Cost per number of claims Medicare child GP attendances 23 613 $21.00 $19,780.95 $85.26 53 313 $17.85 other 74 $17.85 Specialist 104 173 $54.35 $15,365.50 $66.23 attendances 105 139 $27.20 116 37 $47.95 other 15 $27.20 Diagnostic 11309 46 $16.70 $4,236.30 $18.26 11312 43 $23.60 11324 56 $20.95 11327 69 $12.55 other 33 $12.55 Anaesthesia 17603 187 $27.20 $25,400.55 $109.49 17706 71 $63.90 17707 195 $74.55 17708 12 $85.20 other 8 $27.20 Surgery 41632 234 $133.80 $45,537.10 $196.28 41674 6 $56.25 41647 13 $61.60 41764 15 $68.75 41789 29 $165.60 41801 69 $91.30 other 17 $56.25 X-rays 57900-45 8 $42.25 $1,559.35 $6.72 58503 7 $42.25 58509 3 $35.60 other 23 $35.60 Pathology 65007 16 $14.65 $3,866.45 $16.67 65021 23 $27.60 other 65… 19 $13.95 69205 23 $18.30 69207 8 $28.05 69211 10 $39.50 69217 29 $17.50 other 84 $14.10 Total 2720 $115,746.20 $498.91
329 Perisurgery costs for children (N=149) who had tonsillectomy
During the entire episode surrounding the performance of tonsillectomy, 1466 MBS claims were made by the 149 children who had this procedure, alone or with another ENT procedure.
Table 13.2 Tonsillectomy perisurgery benefits paid by Medicare MBS item group MBS item Number Item benefit Total cost to Cost per number of claims Medicare child GP attendances 23 309 $21.00 $8,750.15 $58.73 36 13 $38.00 53 82 $17.85 other 17 $17.85 Specialist 104 100 $54.35 $8,713.20 $58.48 attendances 105 34 $27.20 110 12 $95.80 116 20 $47.95 other 9 $27.20 Diagnostic 11309 10 $16.70 $1,134.75 $7.62 11312 16 $23.60 11324 9 $20.95 11327 22 $12.55 other 10 $12.55 Anaesthesia 17603 126 $27.20 $15,737.30 $105.62 17706 9 $63.90 17707 84 $74.55 17708 62 $85.20 other 7 $27.20 Surgery 41632 33 $133.80 $30,448.05 $204.35 41674 6 $56.25 41647 5 $61.60 41764 2 $68.75 41789 144 $165.60 41788 5 $123.15 other 14 $56.25 X-rays 57903 5 $42.25 $778.35 $5.22 57945 2 $38.85 58503 4 $42.25 58509 1 $35.60 other 8 $35.60 Pathology 65007 24 $14.65 $4,971.30 $33.36 65021 54 $27.60 other 65… 38 $13.95 69205 5 $18.30 69207 4 $28.05 69211 4 $39.50 69217 7 $17.50 73903-15 92 $14.10 other 58 $14.10 Total 1466 $70,533.10 $473.38
330 In Table 13.2 it is seen that average benefits paid by Medicare for children who had tonsillectomy amounted to $473.38 per child.
Although the total amount of claims received per child for myringotomy was very similar to the total for tonsillectomy, the composition of these claims differed, as shown in Table 13.3.
Table 13.3 Comparison between tonsillectomy and myringotomy perisurgery costs per child by type of MBS item MBS item group Tonsillectomy Myringotomy GP attendances $58.73 $85.26 Specialist attendances $58.48 $66.23 Diagnostic $7.62 $18.26 Anaesthesia $105.62 $109.49 Surgery $204.35 $196.28 X-rays $5.22 $6.72 Pathology $33.36 $16.67 Total $473.38 $498.91
Table 13.3 shows that, on average, children who had myringotomy made more claims for consultations and diagnostic tests, while those who had tonsillectomy made more pathology claims.
Perisurgery costs for children who had ENT surgery
In order to combine the above perisurgery cost estimates for tonsillectomy and myringotomy and obtain an estimate for all 359 children who underwent ENT surgery, reference was made to the type and combinations of surgery in Table 6.2. These combinations are shown together with the derived cost estimates in Table 13.4.
331 Table 13.4 Type and combination of ENT surgery with estimated costs
Type of ENT surgery Number of Cost estimate children Tonsillectomy or 100 $473.38 Tonsillectomy & adenoidectomy Myringotomy & tonsillectomy or 49 $664.51* Myringotomy & tonsillectomy & adenoidectomy Myringotomy & adenoidectomy 74 $590.21* Myringotomy only 109 $498.91 Adenoidectomy only 27 $399.08** All ENT surgery 359 $525.71 (weighted average) * These children were given the myringotomy perisurgery cost structure plus the respective cost of the tonsillectomy or adenoidectomy procedure ** These children were given the same perisurgery cost structure as tonsillectomy, adjusted for the difference in procedure cost
Table 13.4 shows the estimate of the weighted average perisurgery cost for all 359 children who underwent any type of ENT surgery to be $525.71.
332 Difference between surgery and non-surgery group in total MBS claims over 8 years
It has already been demonstrated that the performance of ENT surgery did not result in reduced subsequent use of medical services (Tables 12.4–12.6 and 12.9-12.11). A comprehensive comparison of claims between these children and those who did not have surgery from birth until 8 years of age was estimated by a further regression analysis.
Estimated claims resulting from this analysis are shown in Table 13.5.
Table 13.5 Number of MBS claims as a factor of age and ENT surgery status, taking into account effect of perisurgery period.
Parameter Parameter Standard P value estimate error Claims at month 1 0.87492 0.00342 <0.0001 Change in number of claims per month -0.00578 0.00006 <0.0001 ENT group extra claims at month 1 0.56496 0.01435 <0.0001 ENT group – extra change per month -0.00335 0.00026 <0.0001 Extra claims during perisurgery 2 months prior 0.79305 0.10637 <0.0001 period for tonsillectomy 1 month prior 1.37652 0.10638 <0.0001 Month of surgery 4.48618 0.10638 <0.0001 Extra claims during perisurgery 2 months prior 0.56248 0.13422 <0.0001 period for adenoidectomy 1 month prior 1.03028 0.13422 <0.0001 Month of surgery 4.09218 0.13422 <0.0001 Extra claims during perisurgery 2 months prior 0.62364 0.09410 0.0001 period for myringotomy 1 month prior 1.05203 0.09410 0.0001 Month of surgery 3.39757 0.09410 0.0001 1 month post 0.35454 0.08411 0.0001 R2 = 0.0351
Regression results in Table 13.5 show that each of the factors tested had a highly significant effect. The low R2 value does not negate the significance of the factors tested, and would have been higher if a seasonality factor (not of interest here) had been included (refer to Table
333 6.2, where age and seasonality were both entered into the model predicting total claims resulting in R2 = 0.7079).
Monthly claims by both groups of children were high at birth and declined slowly thereafter.
In their first month of life, children who did not have surgery made 0.9 claims on average, which declined thereafter by 0.00578 claims per month. Children who had ENT surgery made 0.565 more claims than the other group initially, with an average 1.44 claims in their first month of life, which then declined at the greater rate of 0.00913 claims per month.
From Table 13.5, total estimated perisurgery effects were as follows: the sum of extra claims during the perisurgery period, including month of surgery, amounted to 6.7 for tonsillectomy,
5.7 for adenoidectomy and 5.4 for myringotomy.
To examine how well the model fitted the observations and to determine whether the greater rate of decline among the surgery group might have led to convergence of the two groups at some point, estimated claims per month for the 96-month period were calculated for each group. Although adjusted for in the above model, the extra claims by the ENT group during their perisurgery periods were not included in these estimates, both for reasons of comparability and since the perisurgery months differed by child. These estimated claims together with observed counts of claims per month are shown in Figure 13.1.
334 Figure 13.1 Observed and estimated MBS claims per month by age: children who had ENT surgery compared with those who did not
3
2.5
2
1.5
1 Ave claims per month per Ave claims 0.5
0 1 5 9 131721252933374145495357616569737781858993 Age (months)
No ENT-estimated ENT-estimated No ENT-observed ENT-observed
It can be seen in Figure 13.1 that the trend line, by having omitted seasonality from the model, fails to follow the seasonal fluctuations, which explains the low R2 value obtained in the model. However, a linear model appears to explain the data adequately, with the exception of the initial values which represent the extremely high levels of claims observed during the first three months of life by both groups, reflecting not only close medical observation during this vulnerable period, but also claims related to immunization. Figure 13.1 also shows that no convergence between the two groups occurred during these children’s first eight years of life, even though the rate of decline was higher for the ENT group. This final analysis confirms that, after adjusting for extra claims during the perisurgery periods, the level of claims remained higher at all ages for children who had ENT surgery than for children who did not.
335 For each group, estimated MBS claims had already been calculated to produce values for
Figure 13.1. These were summed for each group. The results were as follows. Over the total period of 96 months children who had ENT surgery made an estimated average 95.7 claims, excluding the additional claims made during their perisurgery periods. Children who did not have ENT surgery made an estimated average 57.1 claims, 38.6 claims fewer than the total number of claims made by children who had ENT surgery.
However, since claims during the perisurgery period had already been counted (Table 13.5), 4 months of non-perisurgery claims were subtracted from these children’s totals, to avoid double counting. Since individual perisurgery periods were distributed throughout the 8 years and since claims diminished with age for all children, it was decided to arbitrarily designate weeks 48 to 51 as the proxy perisurgery period and to subtract the estimated claims corresponding to these 4 weeks from the total. Accordingly, total claims for those who had surgery were reduced to 91.8, and hence their net adjusted excess over the non-surgery group became 34.7 claims. Costs were then assigned to these excess claims.
A conservative approach was taken in assigning costs to these excess claims. Since 77.3% of all claims were for GP attendances (Table 6.5), and since for these children some of the far more costly specialist and diagnostic claims had already been counted in the estimate of perisurgery costs, all excess claims were conservatively assumed to represent GP attendances.
The November 1997 MBS benefit for such attendances was $21.00 (representing 85% of the scheduled fee). Hence the excess cost generated per child during the period between their birth and eight years of age was estimated to be $728.70. To this figure was added the average estimated perisurgery cost of $525.71 (Table 13.4), yielding a total estimated excess
336 cost to Medicare per child who had ENT surgery of $1,254.41 during their first eight years of life.
Estimated annual excess MBS cost for all NSW children who have ENT surgery
The excess cost per year for all NSW children who have ENT surgery was estimated as follows. The current study refers to those children in a one month NSW birth cohort who had
ENT surgery. Over the study period of eight years, these children generated the costs estimated above in excess of costs generated by the remainder of the cohort children who did not have surgery. There is no reason to suppose that, had any other month been nominated as the cohort month of birth, results would have differed. In any one calendar year, the ages of all NSW children younger than eight years are approximately evenly distributed between birth and eight years. Hence the annual average excess claim per child who had surgery could be estimated as $1254.41 divided by eight, or $156.80 per child per year. To obtain this total excess cost for all NSW children, the proportion of cohort children who had surgery at any time during their first eight years, 359 out of 6239 children (5.75%), could be applied to the total NSW population in this age group. For instance, in June 1999 the estimated population aged under eight years was 698,386301. Hence 5.75% of the paediatric population aged under
8 years (40157) could each be expected to generate $156.80 excess costs to Medicare per annum, which makes a total of $6,296,681.64.
337 DISCUSSION
The economic analysis presented in this chapter was aimed at estimating the financial implications of the findings of this study with regard to the children who had ENT surgery.
These children made claims far in excess of those made by the children who did not have surgery. These excess claims were not only those directly related to their surgery, but were in excess of the other children’s claims throughout the period studied. Disregarding the question whether such excess utilisation is avoidable, the full cost to Medicare when applied to the
NSW population has been estimated.
For claims directly related to surgery, the type and number of medical services during the period surrounding ENT surgery, as well as those related to the surgical episode were identified. The number and type of these perisurgery services were examined and costed using the Medical Benefits Schedule. Although these perisurgery claims were separately analysed for tonsillectomy and myringotomy, their ultimate cost to Medicare was remarkably similar at close to $500 per child. When adjusted to allow for the known number and type of combined procedures, the average ENT perisurgery cost per child was estimated to be
$525.71.
To this cost was added the known higher use of services by children who had ENT surgery during the whole eight years, excluding 4 months to avoid double counting of claims during the perisurgery period. This excess use of services throughout the 8 years, which remained unaffected by surgery, was calculated to be $728.70 and added to the perisurgery costs. The result was a total excess cost to Medicare of $1254.41 per child. These amounts were based upon 1997 reimbursement rates and are a conservative estimate.
338
This considerable excess cost represents only the cost to Medicare, which does not fund hospital costs (only, to a limited extent, the cost of the practitioner). Nor does it include costs to private insurance funds or costs to the parents of these children, both direct and indirect, such as travel and work-related expenses.
The financial burden on the community is significant. Application of these costs to the whole
NSW paediatric population resulted in an estimated excess cost to Medicare of $6.3m per annum, a considerable expense to the Medicare system in a climate of scarce resources.
339 Chapter 14 CONCLUSIONS
This chapter presents the major findings and final conclusions of this thesis and proposes directions for further research into paediatric ENT surgery.
Part I Part II Part III Part IV Part V Part VI Research Population Cohort study Guideline Effect of Conclusion background & study: of health compliance ENT surgery aims Epidemiology services on of ENT utilisation subsequent Surgery utilisation
Chapter 1 Chapter 2 Chapter 5 Chapter 9 Chapter 11 Chapter 14 Research Introduction Introduction Introduction Introduction Conclusions & methods background & methods & methods & methods & aims
Chapter 3 Chapter 10 Chapter 6 Chapter 12 ENT Guideline Total cohort Subsequent surgery compliance: utilisation: utilisation: rates: Results & Results & Results & Results & discussion discussion discussion discussion
Chapter 13 Chapter 4 Chapter 7 Economic ENT impact: Effect of cohort guidelines on Results & utilisation: discussion rates Results & discussion
Chapter 8 Comparison: ENT with total cohort: Results & discussion
340 INTRODUCTION
This thesis has addressed major research questions regarding paediatric ENT surgery. The first two questions concerned the epidemiology of ENT surgery in NSW, specifically:
1. What is the level of NSW ENT surgery rates and their trends over time, and how
compatible are these rates with international rates?
2. Was guideline dissemination in NSW associated with changes in rates of surgery and
have guideline recommendations been followed?
The next questions focussed on the children who had these therapeutic interventions, and on whether their consulting behaviour prior to surgery could suggest a possible reason for its performance, and, if so, whether surgery produced a change. Specifically, the following questions were asked:
3. Prior to surgery, did children who had surgery use more health services than those
who did not have surgery?
4. If so, did surgery result in decreased use of services?
5. What is the impact of ENT surgery on the health system (utilisation of hospital
resources and costs to Medicare)?
The findings of this program of research are summarized in the following table.
341 Table 14.1 Summary of findings from the program of research
What is the level of NSW ENT surgery rates? Incidence of Rate per 100,000 surgery Children aged 0-14 years, 1998/99 1,340 (a) ENT surgery 590 (b) Tonsillectomy 639 (c) Adenoidectomy 772 (d) Myringotomy Males aged 0-4 years, 1998/99 708 (a) Tonsillectomy 944 (b) Adenoidectomy 1,567 (c) Myringotomy Females aged 0-4 years, 1998/99 483 (a) Tonsillectomy 613 (b) Adenoidectomy 999 (c) Myringotomy Males aged 5-9 years, 1998/99 817 (a) Tonsillectomy 930 (b) Adenoidectomy 1,009 (c) Myringotomy Females aged 5-9 years, 1998/99 838 (a) Tonsillectomy 862 (b) Adenoidectomy 765 (c) Myringotomy Males aged 10-14 years, 1998/99 249 (a) Tonsillectomy 191 (b) Adenoidectomy 137 (c) Myringotomy Females aged 10-14 years, 1998/99 436 (a) Tonsillectomy 280 (b) Adenoidectomy 133 (c) Myringotomy Prevalence of Projected risk: 1998/99 estimate surgery Risk of ENT surgery by age 15 years 20.2% Risk of tonsillectomy by age 15 years 8.9% Risk of adenoidectomy by age 15 yrs 9.6% Risk of myringotomy by age 15 years 11.6%
Risk of ENT surgery by age 5 years 8.9% Risk of tonsillectomy by age 5 years 3.0% Risk of adenoidectomy by age 5 yrs 3.9% Risk of myringotomy by age 5 years 6.4%
Actual prevalence: NSW population born 1994/95: Prevalence of tonsillectomy by age 2 yrs 0.1% Prevalence of tonsillectomy by age 3 yrs 0.5% Prevalence of tonsillectomy by age 4 yrs 1.4% Prevalence of tonsillectomy by age 5 yrs 2.7%
Prevalence of myringotomy by age 2 yrs 1.8% Prevalence of myringotomy by age 3 yrs 3.1% Prevalence of myringotomy by age 4 yrs 4.6% Prevalence of myringotomy by age 5 yrs 6.4% Surgical risk Age most at risk of surgery: factors Peak age for tonsillectomy 1998/99 4 years 342 Peak age for adenoidectomy 1998/99 4 years Peak age for myringotomy 1998/99 4 years Gender most at risk of surgery: Tonsillectomy 1998/99 M:F ratio 0-4 years 1.43 Tonsillectomy 1998/99 M:F ratio 5-9 years 0.98 Tonsillectomy 1998/99 M:F ratio 10-14 years 0.59 Adenoidectomy 1998/99 M:F ratio 0-4 years 1.49 Adenoidectomy 1998/99 M:F ratio 5-9 years 1.09 Adenoidectomy 1998/99 M:F ratio 10-14 years 0.81 Myringotomy 1998/99 M:F ratio 0-4 years 1.55 Myringotomy 1998/99 M:F ratio 5-9 years 1.22 Myringotomy 1998/99 M:F ratio 10-14 years 1.13 Characteristics Number of children 359 of cohort Total claims for ENT surgery 581 children who Number of boys who had ENT surgery 226 had privately Number of girls who had ENT surgery 133 funded ENT Number of children who had tonsillectomy 149 surgery Number of children who had adenoidectomy 111 Number of children who had myringotomy 232 % of 232 children who had myringotomy more than once 25% Prevalence of tonsillectomy/adenotonsillectomy per 1,000 23.9 cohort children by age 8 years Prevalence of adenoidectomy/1,000 cohort children by age 8 17.8 Prevalence of myringotomy/1,000 cohort children by age 8 37.2 What were the trends in ENT surgery rates over time? Change in rates Children aged 0-14 years per annum (1981-98/99) Rate trends (a) ENT surgery +1.1% p.a. (+21%) 1981 - 1998/99 (b) Tonsillectomy +0.2% p.a. (+3.2%) (c) Adenoidectomy No change (d) Myringotomy +1.9% (+39%) Males aged 0-4 years (a) Tonsillectomy +2.5% (+54.5%) (b) Adenoidectomy +1.8% (+37.8%) (c) Myringotomy +4.0% (+98.9%) Females aged 0-4 years (a) Tonsillectomy +1.8% (+37.8%) (b) Adenoidectomy +1.3% (+25.9%) (c) Myringotomy +3.7% (+90.1%) Males aged 5-9 years (a) Tonsillectomy -0.8% (-13.3%) (b) Adenoidectomy -1.4% (-22.3%) (c) Myringotomy -0.3% (-5.6%) Females aged 5-9 years (a) Tonsillectomy -1.0% (-16.2%) (b) Adenoidectomy -1.6% (-24.3%) (c) Myringotomy No change Males aged 10-14 years (a) Tonsillectomy +0.7% (+12.4%) (b) Adenoidectomy +0.9% (+16.5%) (c) Myringotomy -1.0% (-15.5%) Females aged 10-14 years (a) Tonsillectomy -0.5% (-8.5%) (b) Adenoidectomy No change (c) Myringotomy No change Morbidity Proportion of children presenting to GPs who are diagnosed No increase between trends with acute otitis media 1990/91 and 1998/99 343 Did guideline dissemination in NSW affect the rate of surgery and were guideline recommendations followed? Guideline Indications for myringotomy compliance Percentage of children who claimed for at least 3 GP visits in 78.4% the six months preceding surgery Percentage of children who had a hearing test prior to 54.7% surgery Between 1988/89 and 1998/99 Diagnosis % (change) (a) indicated diagnosis “OME” 82.4% (3.7% increase) (b) non-indicated diagnosis “acute otitis media” 0.8% (82% decrease) (c) non-indicated diagnosis “acute respiratory” 0.05% (72% decrease) (d) indicated diagnosis “hearing related” 1.0% (60% decrease) Indications for tonsillectomy Number (%) of children who claimed for polysomnography 2 (1.3%)
Between 1988/89 and 1998/99 Diagnosis % (change) (a) indicated diagnosis “chronic disease of tonsils and 93.2% (5.4% increase) adenoids” (b) non-indicated diagnosis “acute respiratory” 2.0% (78% decrease) (c) indicated diagnosis “apnoea” 2.2% (5-fold increase) Prior to surgery, did children who had surgery use more health services than those who did not have surgery? Population Full cohort: Number of children 6239 health service Total MBS claims 372,815 utilisation: Average claims per child 59.8 birth to 8 Average claims per boy (n=3194) 62.4 years Average claims per girl (n=3045) 57.0 Median claims per child 50.5 Median claims per boy 52.7 Median claims per girl 48.9 Median claims for GP consultations 38 Median claims for specialist consultations 1.5 Claims for GP consultations as % of total claims 78.6% % children who claimed at least once for optometry 29.2% Average claims per child: (a) In 1st year 11.4 (b) In 2nd year 9.4 (c) In 3rd year 7.7 (d) In 4th year 7.6 (e) In 5th year 6.9 (f) In 6th year 6.5 (g) In 7th year 5.4 (h) In 8th year 4.9 Comparative ENT children use of health Average claims per child 103.8 services Median claims per child 96.4 (Aggregates) Median claims for GP consultations 62.3 Median claims for specialist consultations 8.9 Claims for GP consultations as % of total claims 64.7% % children who claimed at least once for optometry 41.2%
Non-ENT children Average claims per child 57.1 Median claims per child 48.1 Median claims for GP consultations 38.4 Median claims for specialist consultations 1.5 Claims for GP consultations as % of total claims 78.6% 344 % children who claimed at least once for optometry 29.2% Comparative ENT children No. services (99% C.I.) use of health In 1st year 16.6 (16.0-17.2) services In 2nd year 15.3 (14.5-16.0) (Modelled In 3rd year 13.9 (13.1-14.8) estimates) In 4th year 12.6 (11.7-13.6) In 5th year 11.3 (10.2-12.4) In 6th year 10.0 (8.8-11.2) In 7th year 8.7 (7.4-10.0) In 8th year 7.4 (5.9-8.8)
Non-ENT children No. services (99% C.I.) In 1st year 10.0 (9.9-10.2) In 2nd year 9.2(9.1-9.4) In 3rd year 8.4(8.2-8.5) In 4th year 7.6(7.4-7.7) In 5th year 6.7(6.5-6.9) In 6th year 5.9(5.7-6.1) In 7th year 5.1(4.8-5.3) In 8th year 4.2(3.9-4.5) If so, did surgery result in decreased use of services? Effect of Tonsillectomy surgery on At age <4 years No change trend of health At age 4 years No change service At age 5 years & over No change utilisation Myringotomy At age <3 years No change At age 3 years Reverse in upward trend At age 4 years & over No change
What is the impact of ENT surgery on the health system? Impact of ENT (a) Percentage of paediatric hospitalisation due to ENT 12.2% surgery on surgery, 1998/99 health system (b) Percentage of paediatric hospitalisation due to 5.5% tonsillectomy, 1998/99 (c) Percentage of paediatric hospitalisation due to 5.9% adenoidectomy, 1998/99 (d) Percentage of paediatric hospitalisation due to 6.9% myringotomy, 1998/99 (e) Direct ENT surgery cost to Medicare per child $525.71 (f) Excess cost to Medicare of extra services used over $728.70 8 years per child who has ENT surgery
345 What is the level of NSW ENT surgery rates and trends, and how internationally comparable are these?
ENT surgery is an important child health issue. There remain large areas of uncertainty in the management of common childhood conditions and the appropriateness of surgical intervention. The aim in this part of the research program was to determine whether the level of the three major types of paediatric ENT surgery in NSW was comparable with international levels, whether changes in practice of these therapeutic interventions had occurred over time and what factors were associated with such changes.
The incidence of ENT surgery among NSW children over a lengthy period, 1981-1999, was determined from a comprehensive collection comprising 221,273 hospital records relating to all NSW hospitals, public and private, including day only facilities. In 1998/99, the final study year, the rate of ENT surgery for NSW children aged under 15 years was 13.4/1,000, with rates of tonsillectomy, adenoidectomy and myringotomy being 5.9, 6.4 and 7.7/1,000 respectively.
Between 1981 and 1999, ENT surgery rates in NSW increased by 21%. Myringotomy rates were the main contributors to this overall increase – while tonsillectomy rates increased by
3.2% and adenoidectomy rates remained unchanged, myringotomy rates increased by 39%
(Table 3.7). Both before and during the study period, in NSW and internationally there were large movements in opinion regarding the efficacy of these therapeutic interventions, which were reflected in population rates of surgery.
346 With regard to tonsillectomy, with or without adenoidectomy, in the period prior to 1987,
NSW, in common with other countries, experienced massive declines in rates, largely due to the efficacy of antibacterial treatment of the underlying conditions. NSW rates dropped by two-thirds between 1978 and 1983203, while U.S. rates halved between 1970 and 1977198, and declined a further two-thirds between 1977 and 1987166. Between 1967 and 1980, tonsillectomy rates declined by a similar proportion in the U.K. 160, and, between 1961 and
1985, by 32% in Poland 202.
Following this period of decline, there was a levelling out of rates. Between 1981 and 1991 tonsillectomy rates reported in Scotland were similar to NSW rates found in the current study.
In 1990, the tonsillectomy rate in NSW was 5.5/1,000 children aged 0-14 years and in
Scotland 6.0/1,000 children aged 0-15 years167; both, however, were lower than the Canadian
1990 rate of 7.8/1,000 children aged 1-14 years7. After 1991, NSW rates increased slightly, reaching 5.9/1,000 in 1998/99; however, no international rates covering this period were available for comparison.
By contrast with tonsillectomy, myringotomy rates increased enormously in all countries after
1967. By the late 1970s, glue ear had become the most common reason for surgery among children aged 0-14 years in England and Wales, where rates almost trebled between 1967 and
1980160. Myringotomy rates in NSW were in line with these international levels, rising greatly until 1981. In East Anglia/Oxford rates peaked in 1986, and then began to decline, while NSW rates continued to climb until 1989, when they reached the East Anglia/Oxford level (11.8/1,000), regions with rates above the English norm, and remained at a similar level between 1989 and 1992. However, after 1992 NSW rates continued at approximately this
347 level, in contrast with rates in East Anglia/Oxford, which declined sharply, to 6.8/1,000 children aged 0-9 years in 19971. The 1997 NSW myringotomy rate, by contrast, was
10.6/1,000 children aged 0-9 years, and showed no sign of declining. In the Netherlands too, an easing of rates occurred after 1992164. In 1998/99, the final study year, the NSW myringotomy rate of 7.7/1,000 children aged 0-14 years was almost as high as the peak study rate found in 1992/93 (8.1/1,000, Table 3.2). It is suggested that grommet insertion trends in
NSW may lag about 5 years behind international trends.
Trends in age of children who had surgery
The most interesting finding of this descriptive epidemiology section of the program of research was that the increase in NSW rates was driven solely by increased surgery among the youngest age group, children under 5 years of age. Rates for older children remained static or declined over the study period.
Over the whole period, tonsillectomy rates among children under 5 years increased by 54% for males and by 38% for females. By contrast, rates among children aged 5-9 years decreased, by 13.3% for males and by 16.2% for females, with mixed changes among those aged 10-14 years, where male rates increased by 12.4% and female rates decreased by 8.5%.
Adenoidectomy rates for children aged under 5 years increased, by 37.8% for males and by
25.9% for females, and decreased among those aged 5-9 years, by 22.3% for males and by
24.3% for females. Among those aged 10-14 years, male adenoidectomy rates increased by
16.5% and female rates remained unchanged.
348 This thesis has explored possible reasons for this increase in surgery among very young children. One Canadian working party suggested that, due to the difficulty of diagnosing tonsillitis in patients under 5 years of age, some of these children may be undergoing surgery based wholly or in part upon recurrent non-specific viral URTI 7. Another possible factor driving rates of tonsillectomy among very young children may be increased concerns regarding sleep apnoea125 130 201 211 225. Obstruction of the airways by enlarged tonsils can lead to this serious condition227 228. However, the younger the child, the relatively larger are the tonsils, and the younger the child, the greater the parental concern regarding the child’s respiration during sleep. In the absence of polysomnography, which requires overnight clinical observation, a definitive diagnosis of sleep apnoea cannot be made16 175 176 192 193 230
231, and simple non-obstructive snoring might be confused with apnoea, leading to unnecessary surgery among these young children182. In the current study, the prevalence of tonsillectomy was found to have more than doubled by age 2 years and to be 48% greater by age 3 years among the NSW cohort born during 1994/95 compared with the cohort born six years earlier (Table 3.16). These rates of increase warrant further investigation.
With regard to myringotomy, the current study found that rates of myringotomy in the under 5 year age group almost doubled over the whole study period, while, in the two older age groups, male rates declined (by 5.6% and 15.5% respectively), and female rates remained unchanged. The prevalence of myringotomy by age 2 years was 37% greater among those children born during 1994/95 than among those born during 1988/89, and by age 3 years 36% greater (Table 3.16). The predisposing condition, acute otitis media, which often precedes
OME36, a frequent indicator for surgery, is the most common reason for physician consultation for children younger than 15 years15 23 33 53 56. Acute otitis media is endemic
349 among the very young, and the younger the child, the more frequent the episodes. One U.S examination of physician consultations for the management of otitis media found that, while children under 10 years of age averaged 2.9 visits for otitis media in the year, one quarter of those aged under 2 years had 6 or more such visits59. Acute otitis media has been found to cause 26% of all medical visits by U.S. children between birth and two years of age 58. By age
2 years most children have experienced at least one episode of acute otitis media4 39 41 48 53-55.
There is evidence that this health burden is increasing. In the U.S., the prevalence of recurrent otitis media was found to have increased from 19% in 1981 to 26% in 1988 among preschool children 61, and, in Finland, from 14% in 1978/79 to 21% in 1994/95 among children aged under 1063. Acute otitis media is said to be developing at an earlier age, with the proportion of children having multiple episodes before one year of age having increased over the past decade118. However, by contrast, the NSW general practitioner surveys revealed that management of acute otitis media among children aged 0-14 years actually decreased between
1990/91 and 2000/01 (Chapter 3)51. This finding might have been due to not having limited the analyses to very young children.
There are other factors that suggest increased morbidity. Allergy is an increasing problem worldwide78, including Australia, and is associated with otitis media with effusion76, with chronic rhinosinusitus74 and with tonsillar hypertrophy315. Antimicrobial resistance is also increasing and associated with a decreased rate of eradication of pathogens from middle ear fluid.40 Daycare attendance has been shown to increase the risk of development of resistance
316, as well as the risk of otitis media, possibly by exposing the young child to pathogenic microbes not encountered at home64 65 79 82 317, and to increase the risk of receiving
350 tympanostomy tubes53 81. Daycare attendance has increased in Australia between 1984 and
199985, with rates among children aged under 3 years increasing from 8% to 22% and for those aged 3-4 years from 10% to 66% 318. Hence increased daycare may have contributed to increased rates of morbidity in these young children, leading to surgery.
These changed patient characteristics represent a major shift in the practice of ENT surgery, yet neither guideline made recommendations regarding age and no evidence supporting the efficacy of such surgery at a younger age has been documented.
Did guideline dissemination in NSW affect the rate of surgery and were guideline recommendations followed?
The dissemination of guidelines in NSW was associated with a short-term reduction in paediatric ENT surgery rates. However, in the case of the tonsillectomy and adenoidectomy guidelines, the decrease found in the year following their dissemination may have been related to the worldwide trend during this period rather than to the effect of the guidelines.
There was also a surprising decrease in tonsillectomy and adenoidectomy rates following the publication of myringotomy guidelines. The reason for this may have been that the myringotomy guidelines prompted clinicians to re-evaluate their practice in tonsillectomy and adenoidectomy as well, since rates for these procedures were published at this time163.
Feedback of population-based data on tonsillectomy rates has been found to be associated with significant declines in this procedure in the U.S Wennberg322.
In the case of the myringotomy guidelines, rates were found to have decreased in each of the three years following their dissemination. This finding of a short-term guideline impact
351 agrees with that of Mason et al323 in the U.K. Black et al320 examined rates over a longer period and found decreases to be sustained. However, in the current study, contrary to the findings of Black et al, the decreases were not sustained in the longer term. These contrary findings were reported in a letter published in the British Medical Journal324 (Appendix 6).
As discussed in Chapter 4, the standing and hence the impact of these guidelines among ENT surgeons may have been limited because both sets of guidelines were developed by government agencies rather than otolaryngologic professional groups, although representatives of such groups were included in their development. Black and Hutchings320 attributed the continued decline in the English ENT rates to multiple factors, including publication of guidelines, professional concern about rates, introduction of an internal market into the NHS, and media pressure, all of which created an environment conducive to change.
The latter might also explain the fall in NSW tonsillectomy and adenoidectomy rates following the dissemination of myringotomy guidelines.
Guidelines alone are not sufficient to change practice 286 260. Physicians sometimes disagree with, or distrust, recommendations, preferring to rely on their own experience or that of their colleagues. It has been suggested that the popularity of a surgical procedure follows fashion rather than science, although practitioners are eager that their methods be judged as being scientifically based337.
The cohort analysis provided indirect evidence that one key recommendation of the myringotomy guidelines was being followed, that antimicrobial treatment be attempted prior to surgery; claims for almost all the children who had surgery confirmed that a sufficient number of physician consultations in the six months prior to surgery had occurred to suggest
352 this had been done. However, another key guideline recommendation was that children scheduled for myringotomy have their hearing tested – the analysis found that only half these children claimed for a hearing test prior to surgery. Examination of the cohort children’s claims also revealed that, despite airway obstruction being a key indication for tonsillectomy due to the dangers of sleep apnoea, only two children claimed for polysomnography, in both cases after their tonsillectomy.
The current study did find another more enduring effect of guidelines. Both sets of guidelines made recommendations regarding indications for surgery. By comparing diagnoses recorded as the indication for myringotomy in 1988/89 with those a decade later, 1998/99, an increase was found in the percentage of children with diagnoses listed as indications for surgery by the
1993 myringotomy guidelines (“OME”) and a decrease in those indications not recommended
(“acute otitis media” or “acute respiratory infections”) (Table 4.3). However, this comparison also showed a decline in the percentage of children with a diagnosis of “hearing loss”, which remains a major indication for myringotomy. Regarding indications for tonsillectomy and/or adenoidectomy, the percentage of children with a diagnosis “chronic disease of tonsils and adenoids” increased, while the percentage with the diagnosis, “acute respiratory infections”, declined (Table 4.4). This outcome was consistent with the tonsillectomy and adenoidectomy guideline recommendations. These changes provide some evidence that practice was influenced by the guidelines. The extent to which this reflects a change in documentation practices versus clinical practice is unknown. It may be that, having seen (and presumably read) the guidelines, the practitioner may change the diagnostic label to be more “acceptable” in better reflecting the labels suggested by the guidelines as acceptable indications.
353 Prior to surgery, did children who had surgery use more health services than those who did not have surgery?
Utilisation of health services by a population cohort
In this second phase of the research, the contribution of the child to the performance of surgery was examined. Epidemiological studies usually attribute variation in rates of surgery to physician- and system-based factors, such as the availability of physicians and hospitals, the extent of specialization, the system of remuneration, insurance status, changes in clinical indications for surgery, differences in local medical practice and the clinical judgment of otolaryngologists18. Studies reflect this orientation. For example, one U.K. study documented the conflicting opinions of general practitioners, paediatricians and otolaryngologists regarding the indications for and benefits of tonsillectomy183. Another study in Canada examining small area variation in rates of grommet insertion found the major determinant to be the opinion of primary care physicians rather than that of otolaryngologists 19. Such studies begin with the basic assumption that the physician is the major arbiter of the surgical decision.
Guidelines also reflect this assumption - that physicians determine the level of the surgical threshold. Hence guidelines attempt to influence rates through influencing the physician.
Population morbidity is usually held to play a small part in rate variation183. One Canadian study specifically examining the needs model for explaining variation found no relationship between surgical rates in a geographical area and self-reported poor health238. Bisset, however, has suggested differences between children might be a factor, in that the higher rates of tonsillectomy found among children residing in regions of low socioeconomic status might be due to poorer health, a result of deprivation and poor nutrition167, and Black has suggested variation in parental demand as another, though difficult to measure, factor18.
354 In contrast, the current research examined the contribution of the children who had surgery to the surgical decision, as revealed by their claims for medical services prior to surgery. No previous Australian or international study has undertaken an analysis of health services utilisation among children in this way. An opportunity was seen whereby information routinely collected by the Australian health care system, Medicare, could be exploited to yield the health care history of a complete cohort of children. It was hypothesized that comparison of the patterns of health service utilisation by the children who had surgery with patterns of children who did not might reveal a reason for surgery.
In order to make such a comparison, it was necessary to first establish a baseline for the paediatric utilisation of health services. To determine this, a large population cohort (6239 children) was identified, and their claims for medical services followed retrospectively from birth to 8 years of age.
This baseline analysis revealed that this cohort of children made a total of 372,815 MBS claims for medical services during the 8 years, an average 59.8 claims per child, with boys making more claims than girls (62.4 claims compared with 57.0), and claims diminishing by age, from 11.4 claims in the first year of age to 4.9 in the 8th year. Most claims were for physician attendances (77.3% for GP attendances and 8.1% for specialist attendances), with other major categories of claim being diagnostic procedures, investigations and imaging
(3.4% of total, average 2.0 claims per child), pathology (8.3%, average 5.0/child), optometry
(0.9%, average 0.6/child) and surgical operations (1.1%, 0.6/child). There was marked seasonality, with claims during spring, autumn and winter being respectively 27.5%, 36.9% and 56.6% higher than during summer. Over the 8 years, children residing in NSW
355 metropolitan areas claimed for more services than rural children, who made fewer claims in all health service categories.
The main findings of these aggregate results were verified and refined by considering individual children. These individual analyses required the matching and chronological ordering of each child’s records. The distribution of service utilisation by individual children over the 8 years was skewed. Hence for total claims as well as for every other category of claim, median claims per child were found to be lower than average claims, due to the influence of a few individuals who made a great number of claims over the 8 years.
When considered individually, boys were still found to make more claims for medical services, including surgery, than girls. This is not a new finding. The work of Black160,
Bisset167 and Klein23 are examples where the preponderance of boys having disease and surgery has been noted. This gender difference has been found from a very early age – in
Japan, infant boys (aged 8-11 weeks) were found to have significantly more obstructive sleep apnoeas than girls338, while, among 3-year-old Danish children diagnosed with OME, the effusion was found to last longer among boys than girls339. Boys are also more likely to develop complications following surgery than girls, as observed in their higher incidence of myringosclerosis following tube insertion (71% vs 31%) referred to in Chapter1139. In the current analysis, boys were found to have a higher use of every type of health service, evident from their 1st month of age. Their higher use of medical services such as specialist consultations (male: female ratio 1.29, Table 6.6) probably reflects a higher rate of illness, while their higher use of surgical services, which include wound repair, might be considered to result from their propensity to play rougher games. However, such reasoning does not
356 sufficiently explain their higher use of other services, such as optometry (male: female ratio
1.05, p=0.0566). The reason for this gender imbalance remains unknown.
This cohort claims analysis has established a hitherto unknown detailed population baseline for the paediatric use of medical services in NSW from birth to 8 years of age.
Identification of cohort children who had ENT surgery
Because these Medicare claims included the partial reimbursement of privately funded surgery, it was possible to identify children who had such surgery at any time during the 8 years. In this cohort analysis, due to their matched records, more accurate rates of the number and types of privately funded ENT surgery undergone by individual children over a number of years were obtainable than those obtained from the epidemiological analysis of hospital data, which are based upon episodes rather than individuals.
This analysis found that 359 of the 6239 cohort children (57.5/1,000) claimed for privately funded ENT surgery over the 8 years; however, 581 such claims were made. One hundred children claimed for tonsillectomy or tonsillectomy/adenoidectomy, 27 for adenoidectomy alone and 232 for myringotomy. Of the children who claimed for myringotomy, 53% also claimed for tonsillectomy and/or adenoidectomy, and 25% claimed more than once for myringotomy. Boys outnumbered girls, with 226 males compared with only 133 females having undergone ENT surgery by eight years of age. Children from rural areas had lower rates of this privately funded ENT surgery.
357 This analysis found that, among this cohort of children born in January 1990, many had surgery at very early ages, which underlines the previous hospital data findings of the shift to surgery at an earlier age. Among children who had tonsillectomy or tonsillectomy/adenoidectomy, 4 years was the most common age, while among those who had adenoidectomy alone the most common age was 3 years, and among those who had myringotomy, 3 years. During their 1st year of age 1.6/1,000 cohort children claimed for their first myringotomy, 7.4/1,000 claimed during their 2nd year and 5.4/1,000 during their 3rd year, making the prevalence of privately funded myringotomy among this cohort 14.4 /1,000 children by age 3 years. By comparison, population prevalence of myringotomy obtained from summing surgery incidence rates over consecutive years from the hospital data was estimated at 27.6/1,000 children aged 3 years (Table 3.16), which, taking into account that the latter prevalence includes publicly funded surgery, compares reasonably well with the cohort prevalence.
Comparative use of health services by children who did or did not have surgery
The utilisation of services by these children was contrasted with the remainder of the cohort who did not claim for surgery. In this contrast, arising naturally among members of the same cohort, population characteristics such as age and gender were automatically controlled.
Hence any differences found between the groups must be attributable to inherent differences arising from their membership of a specific group, that is, the group of children who have privately funded elective surgery.
In the initial bivariate analysis which compared total utilisation, claims for medical services were aggregated for each group. This analysis showed that children who had ENT surgery
358 made an average of 103.8 claims during their first 8 years, while children who did not have surgery made only 57.1 claims. The respective groups claimed for 67.2 compared with 44.9
GP consultations and 13.2 vs. 4.3 specialist consultations. These differences between the groups persisted for other health services, with 90.5% vs. 57.9% making at least one claim for diagnostic tests, 89.1% vs. 65.9% at least one claim for pathology, and 41.2% vs. 29.2% at least one claim for optometry.
It was considered possible that the differences found in this initial simple aggregation of service utilisation might have been spurious, due to extra claims made during the hospital episode, as well as claims related to preparation for surgery and aftercare. Hence a more complex analysis was undertaken to test whether the higher utilisation by the surgery group resulted from their ENT-related condition and was confined to the period pre-surgery. This multiple linear regression analysis compared the surgery and non-surgery groups in terms of number of claims per month of age, taking into account, for the surgery group, only those months pre-surgery. Since individual children had surgery at varying ages, these pre-surgery periods were unique to each child who had surgery.
This regression analysis found that in their first month of age the surgery group made an estimated average 1.39749 claims for medical services compared with 0.87492 for the non- surgery group. Claims for both groups declined by age, by 0.00893 claims per month for the surgery group and by 0.00578 claims per month for the non-surgery group. Despite their higher rate of decline, pre-surgery monthly claims of the surgery group never converged with those of the non-surgery group at any age, but remained at a higher level throughout their pre- surgery periods.
359
Hence it was established that the group who had surgery had a higher rate of use of medical services prior to their surgery, which could suggest a reason for such intervention.
If the prior use of services by children who had ENT surgery was higher, did surgery result in decreased use of services?
Having found that children who had surgery used more services prior to their surgery, the next analysis addressed this question, whether ENT surgery resulted in a reduced rate of utilisation. The initial aggregate analysis, which compared total claims for each child in the year before with claims in the year after surgery, showed a decline post-surgery. However, this crude analysis failed to consider either the known effect of diminishing claims with age or the extra services perisurgery. Multiple linear regression models were again set up to measure the effect of surgery on claims while taking these factors into account. For these analyses, owing to some children having claimed for more than one ENT procedure, two main groups were formed, ‘tonsillectomy’, which included tonsillectomy or tonsillectomy/adenoidectomy or adenoidectomy alone, and ‘myringotomy’, which included all who had myringotomy, whether alone or in addition to tonsillectomy or adenoidectomy. Since initial analysis had shown that the age at which surgery was performed affected the level of claims, each of these two groups was further subdivided into three: those who had surgery at the most common age, or when younger or older. The first 2 months of age, where claims were universally high, were omitted as they distorted the fit and were irrelevant to these analyses.
Following tonsillectomy, there was no change in the level or trend of claims for any group.
Among those who had surgery when relatively young (< 4 years), there was a high initial
360 level of claims (1.880 in their third month of age), which declined slowly over time (by 0.023 claims per month) (Table 12.4). Children aged four years at the time of their tonsillectomy had a slightly lower initial level of claims (1.663), which then declined by 0.011 claims per month (Table 12.5), while children who were older (aged 5 years or older) at time of tonsillectomy had a much lower initial level of claims (1.259) than the previous groups, with a slower decline over time (0.006 claims per month) (Table 12.6).
Similarly most children who had myringotomy, those who had surgery when younger or older than the most common age, did not change their level or trend of claims post-surgery. Those who had surgery when relatively young (<3 years) had a high initial level of claims (1.811 in their third month of age), which then declined by 0.019 claims per month (Table 12.9), while children older than 3 years at time of myringotomy had a lower initial level of claims (1.036), which declined more slowly over time (by 0.0046 claims per month) (Table 12.11). In contrast, among those children aged 3 years at time of myringotomy, there was a change post- surgery. While their initial level of claims (0.834) was similar to that of the oldest group, their claims increased at a rate of 0.012 per month until the time of surgery, after which they declined by 0.011 per month (Table 12.10). However, this decline did not result in their level of utilisation dropping to that of children who did not have surgery, but only to that of the other children who had myringotomy.
This is the first study to demonstrate the association between ENT surgery and subsequent health services use. The study has clearly shown that, in most cases, ENT surgery did not reduce future use. Following surgery, high levels of service utilisation continued. If the parents of these children had expected surgery to reduce the necessity, perceived or real, for
361 frequent doctor consultation, they would have been disappointed. One of the benefits attributed to tonsil or adenoid surgery is a reduction in recurring or chronic problems that have occasioned repeated medical visits207. In Canada it has been reported that tonsillectomy saved between one and one and a half episodes of respiratory illness per patient over the two years following surgery219. However, in the latter study the number of children in the comparison groups was small (approximately 30), and the authors speculate that a diagnosis of respiratory illness in a presentation following surgery could possibly be ambiguous due to the knowledge of the physician that tonsillectomy had been performed. They conclude that such a small saving in episodes may not be worth the costs and risks of a tonsillectomy operation.
The findings of the current study, where no diminution in the rate of claims for medical services was found post-surgery, are in puzzling contrast to these Canadian findings and to the many studies which report parental satisfaction with the outcome of surgery221 223 224 340.
There may, of course, be unacknowledged psychological reasons for such post facto endorsement of surgery. That is, the parents would need and want to feel that the outcome of the procedure was worth the anxiety, expense and pain it caused. Another reason for their endorsement could be that simple observation of claims pre- and post-surgery might detect a reduction, rendered spurious when sophisticated statistical methods to take the effect of age into account are used. Such statistical techniques are not available to a parent who may observe a decline in medical consultations in the 6 months or year following surgery, and attribute this decline to the surgery, without being aware of the effect of maturity on claims, which has been revealed in the current research.
362 The findings of this study suggest that the higher use of services and surgery may be linked and not consequential.
Implications of utilisation characteristics of children who had ENT surgery
This study has found that, both before and after surgery, from birth and throughout a period of
8 years, these children used above average amounts of universally available medical services.
This is a surprising finding for Australian children, considering that these services represent mainly primary care services. In many other countries, it might be argued that, since the cohort children identified as having had surgery were privately insured, their higher level of health care could be due to their belonging to a higher socioeconomic class and thus having greater access to care. In the U.S., low-income families lack access to important health services, have fewer visits for preventive and follow-up care and use fewer diagnostic procedures341. However, in Australia there is universal access to primary medical care, so, although income level and health insurance might be associated with higher rates of surgery, as found in New Zealand172, these factors ought not to impact directly on the use of primary services by the economically disadvantaged. However, there may be other indirect factors associated with economic disadvantage, such as lack of transport or inflexible parental working arrangements, which might have an impact on use of services. In some areas primary care physicians demand a co-payment for service in excess of that paid by Medicare and this could also have an impact. Hence it is possible that at least part of the lower utilisation found among the children who did not have surgery represents unmet health care needs.
363 The size and consistency of the differences found between children who have privately funded ENT surgery and those who do not suggest that the differences are real. This group of children was truly different from their peers. One possible explanation is that such children are less healthy from birth, frail and sickly children who need frequent medical attention. A further possibility is that their parents have a lower health care seeking threshold and are particularly conscientious in seeking health services for their children, and, in addition, have no barriers in their access to services. Evidence to support this latter hypothesis was provided in the finding that 41% of children who had ENT surgery had at least one optometrical examination compared with only 29% of the control group, a ratio of 1.4:1. Optical problems are not usually a symptom of under par health. Rather this suggests that the parents of these children seek health care both in response to specific illness and also possibly as a preventive strategy, or to receive reassurance regarding their child’s health.
Black in a case-control study found that families with children who had undergone surgery for glue ear had a different ‘health culture’ compared with the controls174. These parents viewed their children as having presented significantly more developmental problems than did parents of the control group, and were themselves more conscious of health promoting activities.
Another study found that many factors, such as young age and a parental interpretation that the illness was atypical, influence a parent’s decision to seek medical care, not only because they believe an illness required treatment, but also because they seek reassurance rather than specific treatment342. In the current study, the higher rate of consultation prior to surgery might itself act as a confirmation of the parents’ perception that their child had more developmental problems than normal, which, in turn, could justify the surgical decision, both to themselves and to their physicians.
364
The decision to consult a health provider is based not simply on the presence of medical problems, but is a complex mix of social and psychological factors343. Saunders examined factors influencing the decision to seek medical advice and found that while parental perception of severity or persistence of infection, fever or earaches predicted physician consultation, parents’ post-secondary education was also a predictor (OR 4.0, 95% CI 1.1-
14.6)20. A recommendation of the latter study was for better medical education to enable parents to distinguish between important sentinel symptoms and unimportant symptoms and so reduce the rate of inappropriate consultation. Patient attitudes endorsing the benefits of medical treatment (for back pain) have been shown to predict use of services344. Educated parents are likely to be more aware of health issues, but such awareness appears to heighten rather than allay concerns. Swedish children aged 1-5 years in families with low parent education and/or low socioeconomic status were less likely to have had a physician consultation or to have consumed antibiotics during the previous 12 months than children of a higher social status317. Similarly, Roos and Roos have found education to be associated with high rates of elective surgery238. This population subgroup may be aware of the types of medical treatment currently available, attuned to current medical opinion, and yet hold an optimistic view of potential benefits and seize upon any chance of attaining the best possible health for themselves or their children.
There is much in modern life to encourage high expectations of health. The growth of technology, media reportage and the complementary medicine industry all encourage the perception that perfect health is desirable and obtainable, raising expectations of the ability of modern medicine to solve all health problems.
365
The findings of this study raise a further area for future research in terms of understanding the relationship between children’s use of health services and their parents’ attitudes and expectations, particularly given that these factors appear to be contributing to increased risk of surgery among these children.
How can these findings be used?
The current study has identified a new risk factor for paediatric elective surgery. The differences found between the surgery and non-surgery groups were clear, large and consistent. There are several practical uses to which these findings could be put. One potential use would be to predict which children might be at risk of future surgery by counting the number of claims made over specified periods. By consulting Tables 8.9 and 8.10, such children could be identified by counting the number of consultations or other medical procedures claimed from Medicare during the period, and comparing this total with that of the non-surgery group. For example, by consulting Table 8.10 it can be seen that a child who had over 11 medical claims by the end of the first year or over 20 by the end of the second could be considered at risk of going on to have one of the three types of ENT surgery considered in this study.
In order to assess risk of tonsillectomy or myringotomy specifically, Table 12.16 could be used. In this table, it is seen that estimated annual claims of children who did not have surgery were clearly demarked from those who had tonsillectomy or myringotomy at both a relatively younger and relatively older age. None of the outer bounds of the 99% confidence intervals overlap. Hence, by counting annual claims, this table makes it possible to identify and to rank
366 a child’s risk of surgery. Children whose claims are almost double those of the non-surgery group would be considered at risk of having surgery at a relatively young age, while children whose claims are only moderately higher would be at risk of having surgery at the most common age for the type of surgery or older. Such an identification of children at risk of surgery could be useful by triggering early preventive measures, such as might be suggested by a paediatrician.
Identification of children who might benefit from myringotomy
The one group of cohort children for whom there was clear evidence of benefit following surgery in terms of subsequent reductions in health service utilisation was the group who underwent myringotomy at 3 years of age. From birth, in contrast with all other groups whose use of services declined with age, the number of services used by these children increased month by month. This trend continued until their date of surgery in their fourth year, after which it proceeded to decline, but only to the level of the children who had myringotomy when older.
This increasing use of services by these children, in contrast with all other groups, including the group who did not have surgery, clearly indicates the presence of a medical problem. This knowledge has the potential of being used to identify those cases where myringotomy is of undeniable value. A simple count of the number of medical services in each succeeding six- month period would be all that is necessary to identify such cases. Referring to Table 7.10 where expected totals are compared, it can be seen that there need only be a pattern of small sequential increases rather than decreases to signal a departure from the norm and to identify children for whom myringotomy might provide a benefit.
367
What is the impact of ENT surgery on the health system?
ENT surgery has a significant effect on the NSW health system. It is one of the most common reasons for hospitalization among children. In 1998/99, ENT surgery accounted for 12.2% of all hospital separations of NSW children aged 1-14 years, 11.6% of those aged 1-4 years and
17.6% of those aged 5-9 years.
Economic effects of ENT surgery: direct and associated
However, while concern over the economic effects of variation in elective surgical procedures is often limited to the hospital surgical episode, the current study has identified characteristics of the patient population who had such surgery which have implications far beyond the hospital episode. It has quantified substantial non-hospital costs as well as hospital costs incurred by the children who had ENT surgery.
During the first 8 years of life, the cost to Medicare of a child who had ENT surgery in excess of the cost of a child who did not have surgery was estimated conservatively at $1254.41.
This amount included the surgery itself and associated costs incurred during the perisurgery period, as well as the services previously shown to be used by such a child over the whole period between birth and 8 years of age which are in excess of those used by a child who does not have surgery. When applied to the NSW paediatric population and annualised, the excess cost to Medicare generated by children who have privately funded ENT surgery is estimated at $6.3m per annum. This does not include costs to private insurance funds nor costs to the parents of these children, both direct and indirect, such as travel and work-related expenses.
368 Concern over elective surgery has until now focussed only on the implications for the hospital system. This study has demonstrated that the hospital episode is only one element of above average use of health services by children who undergo this elective surgery. The total additional cost generated is considerable and may not be a cost-effective use of scarce health resources.
369 FINAL CONCLUSIONS
The type of research and analysis reported in this thesis has never been undertaken before, and the findings add substantial new knowledge about the rates and factors associated with paediatric surgery in NSW. The first aim of this program of research was to determine ENT surgery rates among NSW children and their long term trends, with reference to international rates. This aim was achieved and comprehensively documented. In summary, the incidence of ENT surgery among NSW children was found to have increased by 21% between 1981 and
1999, with myringotomy rates being the main contributor to this increase. For tonsillectomy,
NSW rates over the period were found to be reasonably comparable with international levels.
However, for myringotomy, while international rates declined by 44% after 1991, NSW rates showed no sign of such a decline. A possible reason for this is that practice in NSW might lag behind international practice.
An innovative analysis of age- and gender-related trends yielded the new finding that the significant increase in the overall surgery rate was driven solely by increased surgery among the youngest age group. Over the study period, rates of myringotomy doubled among children under 5 years of age. Such a major shift in the performance of this surgery towards very young children has not been documented previously. There is some evidence that the health burden of conditions which are endemic among young children and common precursors to surgery is increasing. Social changes, including increased rates of daycare use among young children, reflecting the increased participation of both parents in the workforce, were identified as potential factors contributing to increased surgery rates among this group of children.
370 The second aim of this program of research was to determine the effect of surgical guidelines on rates of surgery in NSW. The production of guidelines is expensive, resource intensive and requires considerable input of professional expertise. While evaluations of the impact of guidelines on surgery rates have been undertaken elsewhere, no such evaluation has previously been undertaken in NSW. Two sets of guidelines aimed at clarifying the threshold for paediatric ENT surgery were disseminated in NSW during the study period, and the current analysis found that their dissemination was associated with only a short-term reduction in surgery rates, which subsequently returned to their previous high levels.
In the next phase of this research, a totally new and original direction was taken. By contrast with other studies, this research was directed towards the characteristics of the children who underwent ENT surgery. This concept arose from the original reasoning that, if for some children this surgery is unnecessary, as studies into variation commonly suggest, then no difference would be found between these children and those who do not have surgery. A unique methodology for measuring any such difference was devised using claims for medical services. No other study has used the potential for longitudinal research provided by the unique identification of Medicare claimants. Use of Medicare data enabled a population cohort of 6239 children to be identified and, within this cohort, children who had privately funded ENT surgery, as a naturally occurring comparison group. The current study used these routinely collected data to retrospectively track the consulting behaviour of this cohort from birth to 8 years of age. Using innovative statistical techniques, age-specific norms of utilisation of medical services by this cohort were established, constituting a hitherto unknown baseline of health care utilisation for the paediatric population in NSW. New
371 detailed knowledge of an age-related decline in claims for medical services among children was identified in this study.
An unexpected difference was found between the 359 cohort children who had ENT surgery and the 5880 who did not. The children who had surgery were truly different from their peers.
These children sought medical advice at a significantly higher rate, not only before their surgery, which could be an expected consequence of the condition which prompted surgery, but also after surgery (excluding the immediate post-surgery period). Their higher rate of utilisation of health services was evident from birth. It could be speculated that these children made more claims simply because they had more health problems. However, these children also made a significantly greater number of claims for services not related to general health nor to ENT conditions, such as optometry services. This indicates that factors other than medical need might be responsible for the higher amount of utilisation.
Further evidence for this interpretation is provided by the finding that, with one limited exception, the performance of ENT surgery did not result in reduced demand for medical services among these children. If the condition that led to surgery had been successfully treated, it must be assumed that consultations following surgery were not ENT related. Hence, the higher utilisation found before surgery was also probably not entirely ENT related.
It is hypothesized that the higher use of medical services by these children may be due to their parents having higher expectations of health, seeking more rapid resolution of minor health problems, and being more diligent and wide-ranging in their use of preventive medical services. Such high frequency of consultation may then act, both for the parent and the physician, as confirmation of the need for more interventionist forms of treatment.
372
This is the first study to demonstrate the association between ENT surgery and use of health services. While these findings refer only to children whose surgery was privately funded, this is the sector most likely to be implicated in possibly unnecessary surgery, since publicly funded elective surgery is subject to long waiting lists and may face more stringent surgical criteria.
ENT surgery is an important area of child health which consumes a significant amount of health care resources, with costs to the health system, to insurers, to parents and to their children. It is suggested that the strength and consistency of the current findings constitute a new risk factor for paediatric elective surgery worthy of further investigation.
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400 APPENDICES
401 Appendix 1
Communication with NHMRC confirming no planned update on tonsillectomy and adenoidectomy guidelines
402 Appendix 2
Permission from Statewide Health Confidentiality and Ethics Committee to utilise Inpatient Statistics Collection data
403 Appendix 3
Example of Inpatient Statistics form
404 Appendix 4
ISC data fields supplied by NSW Health Department for analysis
405 Appendix 5
Published thesis findings in Journal of Paediatrics and Child Health
406 Appendix 6
Published letter to Editor, British Medical Journal, reporting thesis findings
407 Appendix 7
Permission from the Health Insurance Commission and from the NSW Health Department to analyse Medicare data
408 Appendix 8
Supply of HIC data and file contents
409 Appendix 9
NHMRC 1982 Guidelines for Tonsillectomy and Adenoidectomy
410 Appendix 10
NSW Health Department Working Party Guidelines on the management of paediatric middle ear disease
411