Epidemiology of Acute Rheumatic Fever in Lakes DHB 1998-2007

Epidemiology of Acute Rheumatic Fever

in Lakes DHB 1998-2007

Dr George Gray

January 2009 Acknowledgements

Rosemary Viskovic

Phyllis Tangitu

Dr Phil Shoemack

Dr Jim Miller

Frances Ellery

Dr Johan Morreau

Dr Neil Poskitt

Dr Belinda Loring

Mrs Lynette Borissenko

Dr Neil de Wet

Dr Chris Hewison

Executive Summary

Rheumatic fever is a growing problem among Māori and Pacific Islanders in New Zealand.(1) In these ethnic groups, rates equal to or greater than those seen in developing countries are common. In contrast, the condition has been decreasing among the non-Māori/non-Pacific population of the country.(1) The condition increases morbidity and mortality over the lifespan but can be prevented with low cost antibiotics in primary prevention. Similarly, recurrences can be avoided with inexpensive monthly antibiotic prophylaxis. Despite this, rheumatic fever rates for Māori and Pacific peoples are gradually increasing.

This report summarises the epidemiology of acute rheumatic fever (ARF) in the Lakes DHB area. The information in this report illuminates geographic, ethnic, and age patterns of the condition. The high proportion of Māori in the Lakes DHB population makes this report especially pertinent. It is envisaged this report may help to tailor a coordinated approach to reducing ARF in Lakes DHB. The key findings of this report include:

1. Lakes DHB has a higher rate of ARF than is seen nationally (p<0.05). The age standardised incidence of ARF in Lakes DHB for 1998-2007 was 5.6 per 100,000. This compares with a national average during 1996-2005 of 3.4 per 100,000.

2. Māori account for 84.2% of cases overall in Lakes DHB, and 84.5% of cases among 5-14 year olds. This compares with national rates of 47% overall and 59.5% among 5-14 year olds. The higher relative proportion of Māori cases in Lakes partly reflects the relatively small population of Pacific peoples in Lakes DHB.

3. Māori have a significantly greater incidence of ARF in Lakes DHB than is found nationally. The incidence of ARF among Māori aged 5-14 years in Lakes DHB was 43.4 per 100,000, compared with a national average during 1996-2005 of 34.1 per 100,000 (p<0.05). For all age groups combined, Māori had an ARF incidence of 15.6 per 100,000 in Lakes DHB compared with 8 per 100,000 nationally (p<0.05).

4. Notification completeness within Lakes DHB was significantly lower than the national average; 33% of hospital cases were notified compared with 52% nationally (p<0.01).

5. Lakes DHB had a significantly higher recurrence rate of 12% compared with the national rate of 4.9% (p<0.01). Data collected monthly by the Rotorua General Practice Group (RGPG) show that up to 50% of those requiring secondary prophylaxis do not receive their penicillin injections within 5 days of the scheduled date.

6. Overall Lakes DHB had a diffuse distribution of cases of ARF compared with focal areas of high incidence in settlements within the Bay of Plenty District Health Board (BOPDHB). This distribution is more suited to population health approaches to ARF compared with targeted primary prevention programmes.

7. Only one census area unit (CAU) in Lakes DHB met the National Heart Foundation’s (NHF) threshold for the consideration of a targeted primary prevention programme. The 5-14 year age group in Fordlands had a rate of ARF of 186.5 per 100,000 per year for the five year period 2003-7.

Based on these findings it is recommended that:

1. Overall Lakes DHB and Toi te Ora – Public Health (Toi te Ora) focus on community-level interventions as only 1 CAU (Fordlands) convincingly meets the threshold for consideration of a targeted primary prevention programme. These community level interventions should focus on modifiable risk factors for ARF which are mediated through poverty such as household crowding, poor nutrition, smoking, and the exposure of children to second-hand smoke (SHS). This approach will require both organisations working with local and central government, Housing New Zealand, and Work and Income New Zealand.

2. Lakes DHB and Toi te Ora improve the likelihood of those with streptococcal pharyngitis seeking treatment by facilitating the delivery of health promotion and health education activities in high risk communities which educate

children, parents, and teachers of the need for medical review if a throat infection develops.

3. Lakes DHB and Toi te Ora improve the ability of primary care providers to diagnose and treat streptococcal pharyngitis by facilitating the delivery of health education and professional development on this issue for primary care providers.

4. Lakes DHB improve access to primary healthcare by facilitating free general practitioner (GP) visits in the high risk 5-14 year age group along with fully subsidising the cost of a 10 day course of oral penicillin for streptococcal pharyngitis.

5. Lakes DHB and Toi te Ora reduce ARF recurrence rates by developing a register of those requiring secondary prophylaxis which alerts relevant personnel when medication is overdue.

6. Lakes DHB and Toi te Ora increase ARF case notifications from secondary care by facilitating education for paediatric staff on the detection, management, and notification of ARF along with the epidemiology of the condition in Lakes DHB. In conjunction, Toi te Ora should provide ongoing quarterly feedback to clinicians on the number of cases notified in order to capture any which have been missed.

Contents

Acknowledgements ...... 2 Executive Summary ...... 3 Contents ...... 6 List of Figures ...... 7 List of Tables ...... 7 Abbreviations ...... 8 1 Introduction ...... 9 1.1 Aims and Objectives ...... 10 2 Methods ...... 11 2.1 Data Collection Window ...... 11 2.2 Case Data ...... 11 2.3 Recurrent Cases ...... 12 2.4 Geographic Classifications ...... 12 2.5 Ethnicity and Age ...... 13 2.6 Statistical methods ...... 13 3 Results ...... 13 3.1 Presentations ...... 13 3.2 Analysis of Notification Data ...... 15 3.3 Incidence...... 16 3.4 Ethnicity ...... 17 3.5 Variation with Time ...... 17 3.6 Variation with Age ...... 19 3.7 Variation with Geography ...... 20 3.8 Recurrence Rate ...... 22 4 Discussion ...... 23 4.1 Limitations ...... 26 5 Recommendations ...... 26 References ...... 32

List of Figures

Figure 1 Annual notifications and number of ARF discharges from Lakes DHB hospitals categorised by DHB of residence 1998-2007...... 15 Figure 2 Crude annual ARF presentations for various ethnic groups usually resident in Lakes DHB 1998-2007...... 18 Figure 3 ARF admissions by month for the total and 5-14 year old population usually resident in Lakes DHB 1998-2007...... 19 Figure 4 Age standardised annualised incidence among various age and ethnic groups usually resident in Lakes DHB 1998-2007...... 20

List of Tables

Table 1 ARF presentations by year and usual DHB of residence 1998-2007...... 14 Table 2 Comparison of national rates of ARF calculated by Jaine for 1996-2005(1) and Lakes DHB incidence and recurrence rates from the current study covering 1998-2007. Overall rates for all ages are age-standardised; 5-14 year age group rates are age-specific...... 17 Table 3 Overall incidence of ARF in territorial local authorities for Lakes DHB residents 1998-2007...... 21 Table 4 Age-specific incidence rates (5-14 years of age) of ARF per 100,000 per year over a 5 year period in selected CAUs in Lakes DHB 2003-7...... 22 Table 5 Age specific (5-14 years) incidence rates of ARF by TLA and DHB 2003- 7.(13)...... 30 Table 6 Age-specific (5-14 years) annual incidence rates of ARF by selected Census Area Unit 2003-7 (13) ...... 30

Abbreviations

ARF Acute rheumatic fever BOPDHB Bay of Plenty District Health Board CAU Census Area Unit CCDHB Capital and Coast District Health Board CMDHB Counties Manukau District Health Board CRHD Chronic Rheumatic Heart Disease DHB District Health Board GP General Practice or General Practitioner LDHB Lakes District Health Board LOS Length of stay NHF National Heart Foundation of New Zealand NZEO New Zealand European and Others PHU Public Health Unit RGPG Rotorua General Practice Group RHD Rheumatic Heart Disease SHS Second-hand smoke TLA Territorial Local Authority WDHB Waikato District Health Board WhDHB Whanganui District Health Board WHO World Health Organization

1 Introduction

Acute rheumatic fever (ARF) continues to be a global problem. The condition is especially frequent in developing countries, with high rates observed in Eastern Europe, the Middle East, Asia, and Australasia.(2)(3) Low rates (<10/100,000/yr) are seen in North America and Western Europe.(2)(3) The World Health Organization (WHO) estimates that 500,000 deaths per year occur as a result of ARF and rheumatic heart disease (RHD), with the global prevalence of RHD approximately 20 million people.(3) The highest documented rates of ARF (374/100,000/yr) have been observed among the indigenous people of Australia and Aotearoa/New Zealand.(2)(3)(4, 5)

Aotearoa presents a two tier picture of ARF incidence. Rates consistent with leading developed countries are seen among the majority of the population who are mainly of European origin.(1)(4, 5) In stark contrast, rates equal to or higher than developing countries are seen among the indigenous Māori population and also among Pacific peoples resident in the country.(4, 5)(1) For example, Māori have 22 times the rate of ARF as Europeans in Aotearoa, while the risk for Pacific peoples is 75 times greater than for Europeans.(1) Additionally, while the rate for New Zealand Europeans and Others (NZEO) has dropped significantly over the past 15 years, the rates for Māori and Pacific peoples have increased.(1) Finally, Māori and Pacific peoples are also more likely to have recurrences of ARF and are also more likely to develop chronic rheumatic heart disease (CRHD).(1)

The costs of ARF and RHD are particularly high. ARF is associated with high morbidity and impairs social, physical, and academic development in the 5-14 year age group most frequently afflicted by the condition.(5) The condition has high social and economic costs for families, requiring time, resources, and attention for the regular medical care required over one or more decades. The 120 deaths per year from RHD in New Zealand typically occur in young adults.(6) At the health provider level the financial impact of ARF/RHD is large; one estimate for the Auckland Area Health Board was calculated at $3.6 million per year (1991 dollars).(7) At the societal level, the morbidity of ARF/RHD during the lifespan results in a significant loss in productivity and societal contribution from those affected.

ARF is a largely preventable condition.(4) The declining trends seen in developed countries and in the European population in Aotearoa demonstrate the impact attainable through clinical and public health interventions at community and societal levels.(8) For example, an intensive primary prevention programme implemented by Costa Rica in the 1970s saw the incidence of ARF drop from 90 per 100,000 at the beginning of the decade to less than 10 per 100,000 in 1990.(9) Similarly, prompt diagnosis and treatment through accessible community health clinics in Baltimore catalysed a fall in ARF incidence from 27 per 100,000 to less than 10 per 100,000 within a decade.(10)

The World Heart Federation has advocated for renewed vigour to combat ARF, and encourages a combination of approaches including health promotion, effective prevention, and accurate surveillance.(11) Similarly, the World Health Organization promotes the collection of high quality epidemiological data as a baseline step to inform efforts which reduce the incidence of ARF.(8) This report represents such a step.

1.1 Aims and Objectives

The central aim of this report was to describe the epidemiology of ARF in Lakes DHB. This report is a continuation of the previous ARF work completed by Toi te Ora – Public Health (Toi te Ora).(12)(13) The information described in this report is provided as a first step to guide the multi-agency approach required to reduce the incidence of ARF in Lakes DHB. This approach may include a combination of population health interventions at a community and district level, in addition to targeted interventions for populations at high risk of ARF. Recently a comparison of ARF in Lakes and other DHBs has been published (see Appendix 1) (1) and placed Lakes DHB as fourth highest for ARF incidence in the country; this review sought to provide greater detail within that result.

This report included three objectives: . to confirm the true incidence of ARF in Lakes DHB by age, ethnicity, and time of presentation. . to identify areas which meet the threshold for consideration of targeted primary prevention programmes.

. to calculate the recurrence rate of ARF in Lakes DHB in order to guide improvements in systems to reduce the incidence of ARF and CRHD in Lakes DHB.

2 Methods

2.1 Data Collection Window

This study examined ARF incidence rates for Lakes DHB for the ten year period 1 January 1998 to 31 December 2007. Case data were obtained from two sources; first, discharge data were obtained from Lakes DHB for the time period 1 January 1993 to 31 December 2007. Second, notification data were collected from Episurv for the 1998-2007 time period. The notifications entered in the Episurv database had recently been updated using ARF cases recorded at the Rotorua General Practice Group (RGPG). This had essentially doubled the number of notifications recorded in Episurv for Lakes DHB.(13)

2.2 Case Data

A case of ARF was defined as an episode coded through hospital discharge from a Lakes DHB hospital between January 1998 and December 2007 - as a result, Lakes DHB residents who were admitted to hospitals in other DHBs were not captured in this analysis. Conversely this methodology results in some non-Lakes domiciled cases being counted. Every case identified on the previous audit or Episurv notifications list was matched with a corresponding hospital discharge. To avoid classifying a recurrence of ARF presenting during the ten year study window as an initial case, data were collected over a period five years prior to the ten year window of interest. Therefore, any cases occurring between 1993 and 1997 would not be counted as initial cases in the 1998-2007 period but would be accurately counted as a recurrence.

Data obtained from Lakes DHB included those cases where ARF was the primary diagnosis at discharge. Diagnostic codes included both International Classification of Diseases (ICD) versions 9 and 10, with the former used until mid-1999. ICD 9 and 10

11 codes for ARF were matched and included the ranges 390-392 (ICD 9) and I00-I02 (ICD 10).

2.3 Recurrent Cases

In keeping with the definition used by Jaine(1), recurrent cases were defined as those which occurred more than 30 days after any previous discharge for ARF. Hard copy case notes were reviewed for individuals where a readmission occurred within a time period of 30 days and a repeat diagnosis of ARF had been coded. This process helped to minimise recounting cases which had been coded incorrectly.

Similarly, where diagnostic uncertainty existed the hard copy case notes were reviewed. If a diagnosis was queried by the clinical team but an individual was treated with secondary prophylaxis the case was categorised as ARF.

2.4 Geographic Classifications

Data were analysed by three geographic variables. First, data were analysed on the basis of presentation to Lakes DHB within the study time period regardless of the usual area of residence at the time of diagnosis. This method captured individuals who resided in another DHB but presented to one of the two hospitals within Lakes DHB during the study period. This approach gave a more accurate account of total utilisation and helped to identify areas contained within the borders of other DHBs but consistently served by Lakes DHB.

Second, cases were organised by those who were resident in Lakes DHB at the time of diagnosis. This approach gave a clearer picture of utilisation by the Lakes DHB resident population and the additional utilisation of Rotorua Hospital attributable to residents of neighbouring DHBs. Third, cases normally resident in Lakes DHB were analysed by census area unit (CAU) and territorial local authority (TLA) to determine any geographic clusters of incidence. Areas of focal incidence may be amenable to targeted intervention programmes.

2.5 Ethnicity and Age

Individuals’ prioritised ethnicity was used to categorise cases for analysis. This method is aligned with the Ministry of Health’s recommended protocol for categorising ethnicity.(14) Data were analysed by three main groups 1) Māori, 2) Pacific, and 3) New Zealand European and Other (NZEO). Separate analyses were performed by age group.

2.6 Statistical methods

The direct method of age standardisation was used with the 2006 New Zealand Census population used as the standard population.(15) Data were analysed using Microsoft Excel 2000 with rates, rate ratios, and variations calculated by gender and ethnicity. An internet-based chi-square calculator was used for tests of independence.(16) A p value of 0.05 was used as the threshold for statistical significance.

3 Results

3.1 Presentations

A total of 77 admissions for ARF were recorded in Lakes DHB hospitals during the period 1998-2007. 19 of these cases were attributable to those usually resident in another DHB at the time of diagnosis. Most presentations from another DHB were from those usually resident in Bay of Plenty District Health Board (BOPDHB) (13 cases). All of the BOPDHB cases were from the Eastern Bay of Plenty with 7 from Murupara, 2 from Kawerau, 2 from Whakatane, and 1 from each of Opotiki and Te Teko. This left a total of 58 cases of ARF contributed from Lakes DHB residents. These data are summarised in Table 1.

Table 1 ARF presentations by year and usual DHB of residence 1998-2007.

Year DHB Total 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Lakes 6 11 2 5 3 4 4 5 8 10 58 BOPDHB 1 1 1 2 5 2 1 13 CMDHB 1 1 2 CCDHB 1 1 HBDHB 1 1 WDHB 1 1 WhDHB 1 1 Total 8 12 4 7 5 11 4 7 8 11 77

Presentations ranged between 4 and 12 cases per year with variation in the proportion of cases contributed by those usually resident in another DHB. In 2003 a total of 7 cases were contributed by other DHBs while in 2004 and 2006 no cases were contributed from other DHBs. In 1999 the highest number of cases attributable to Lakes DHB residents occurred; the total of 12 cases for that year was made up of 11 cases from Lakes residents. The next highest number of cases occurred in 2007 when 10 cases attributable to Lakes residents occurred. The lowest number of cases occurred in 2000 when only 2 Lakes DHB residents were discharged with the diagnosis of ARF. These data are summarised in Figure 1 along with PHU notifications for Lakes DHB residents.

6 Casesyearper

0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year

Lakes DHB Other DHBs Notifications

Figure 1 Annual notifications and number of ARF discharges from Lakes DHB hospitals categorised by DHB of residence 1998-2007.

3.2 Analysis of Notification Data

A total of 23 notifications were logged in the Episurv database for Lakes DHB cases which occurred during the 10 year study period. A high proportion of these cases were only entered into the Episurv database in 2008 following an audit by Loring.(13) Of these 23, 21 were for those usually resident in Lakes DHB. However three of these notifications were anomalous; one of the notifications had a primary discharge diagnosis of asthma and length of stay (LOS) of only 2 days – inconsistent with an attack of ARF. A second case was resident in the Taupo District but presented to Tauranga Hospital. The third notified case had a primary diagnosis of mitral valve disorder on hospital records but met the clinical criteria for ARF on the Episurv record. It is likely that the third case was coded incorrectly at the hospital level. This has implications for undercounting the true number of cases and is explored further

15 in the discussion section. The 19 notified cases of ARF occurring among the 58 discharged from hospital indicates 33% of hospital cases were notified.

3.3 Incidence

When compared with the Lakes DHB resident population of 98,319 recorded at the 2006 census a crude average annual incidence of 5.9 cases per 100,000 was determined. The age distribution for the entire New Zealand population gathered from the 2006 New Zealand Census was used as the standard population. With this data, an age standardised rate of 5.6 per 100,000 was calculated for Lakes DHB during 1998-2007. Previously, Jaine has calculated an age standardised rate of 5.7 per 100,000 in Lakes DHB for the 1996-2005 period based on population figures from the 2001 census.(1) Rates calculated from data in the current study and from Jaine’s study are listed in Table 2.

Table 2 Comparison of national rates of ARF calculated by Jaine for 1996-2005(1) and Lakes DHB incidence and recurrence rates from the current study covering 1998-2007. Overall rates for all ages are age-standardised; 5-14 year age group rates are age- specific.

Annualised Incidence per 100,000 Category Study Total NZEO Māori Pacific Jaine (2008) 3.4 0.8 8 16.6 All ages Current study 5.6 0.6 15.6 13.7 5-14 year Jaine (2008) 14.9 3 34.1 67.1 age group Current study 23.3 2.5 43.4 39.7 Recurrence Jaine (2008) 4.9% 1.9% 5.8% 5.2% Rate Current study 12% 0 12% 0

3.4 Ethnicity

The vast majority of cases in Lakes DHB occurred among Māori. Overall 49 (84.2%) of the 58 cases occurred in Māori whilst in the 5-14 year age group 32 (84.5%) of the 38 cases were from those of Māori ethnicity. Pacific peoples accounted for 5 (8.6%) of the 58 cases, whilst those of European/Other ethnicity contributed only 4 (6.9%) cases to the total. Ethnic variation over time, age groups, and geography are discussed in the following sections.

3.5 Variation with Time

The highest number of cases among Lakes DHB residents occurred in 1999 (11 cases) 2007 (10 cases) and 2006 (8 cases) as shown in Figure 2. Over time, presentation by those of Māori ethnicity remained consistently high whilst presentation by those of Pacific or European/Other ethnicity did not occur in some years.

Cases per year per Cases 4

0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year

Maori Pacific European/Other

Figure 2 Crude annual ARF presentations for various ethnic groups usually resident in Lakes DHB 1998-2007.

Figure 3 illustrates higher incidence during winter months. Especially high admission numbers were seen in the opening and closing months of winter. The seasonal variation of admissions may have implications for the timing of interventions, education, and health promotion.

Number Number of cases 3

2 1

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Total Population 5-14 years-olds

Figure 3 ARF admissions by month for the total and 5-14 year old population usually resident in Lakes DHB 1998-2007.

3.6 Variation with Age

The vast majority of cases in each ethnic group occurred in those aged 5-14 years as shown in Figure 4. Interestingly no cases were reported among those usually resident in Lakes DHB in the 0-4 year age group. Cases in this age group did occur among those usually resident outside Lakes DHB. Overall, where cases do occur Māori and Pacific peoples represent the highest proportion of cases; the incidence among Māori in the 5-14 year age group was 43.4/100 000 whilst among Pacific peoples it was 39.7/100 000. The incidence of ARF was lower in all ethnic groups in the 15-24 and 25+ age groups compared with the 5-14 year age group.

20 Rate/100000

0 0-4 5-14 15-24 25+ Total Age group

Maori Pacific European & Other

Figure 4 Age standardised annualised incidence among various age and ethnic groups usually resident in Lakes DHB 1998-2007.

3.7 Variation with Geography

Incidence rates across the two territorial authorities in Lakes DHB are listed below in Table 3. Population data are based on the 2006 census and may therefore underestimate the incidence of ARF across the fluctuating TLA populations of the 10 year study period. In the Taupo District the calculated incidence was lower than expected for an area where Māori comprise 27% of the population. Within the Rotorua District Māori make up 34% of the total population.(17) If the Taupo District had a similar incidence rate to the Rotorua District an additional 2 cases per year would be expected – i.e. 2.6 cases per year in total compared with the current 0.6 cases per year.

Table 3 Overall incidence of ARF in territorial local authorities for Lakes DHB residents 1998-2007.

TLA Population Cases Cases per year Rate/100,000/yr Rotorua District 65901 52 5.2 7.9 Taupo District 32418 6 0.6 1.9 TOTAL 100325 58 5.8 5.8

Over a ten year period, the incidence of ARF was elevated in specific CAUs throughout the DHB and these are listed in Appendix 3. In the 5-14 year age group several CAUs had rates of ARF above 50/100,000/yr with Pukehangi North the highest at 114.2/100,000/yr with 5 cases occurring. However, in keeping with NHF guidelines,(18) rates over a 5 year period were calculated.

Incidence rates over a 5 year period between 2003-7 from Loring’s report are listed in Appendix 2.(13) These tables provide a comparison of overall rates of ARF in BOPDHB and Lakes DHB. Appendix 2 also allows comparison of incidence rates at the CAU level between the two DHBs. Incidence rates listed in Appendix 2 can be compared with those in Table 4 below. Table 4 provides incidence rates for Lakes DHB for 5-14 year olds over the most recent 5 year period as recommended by the NHF. These results provide a guide for areas potentially suitable for primary prevention programmes. All CAUs in the analysis had small numbers of cases and the results should be viewed cautiously. However, Fordlands had a relatively high number of cases (4 cases) during the 5 year window.

Table 4 Age-specific incidence rates (5-14 years of age) of ARF per 100,000 per year over a 5 year period in selected CAUs in Lakes DHB 2003-7.

All Ethnic Groups CAU Cases Population Incidence Turangi 1 528 37.9 Ngongotaha North 1 507 39.4 Ngapuna 1 99 202.0 Owhata West 1 687 29.1 Owhata East 2 381 105.0 Tikitere 1 516 38.8 Western Heights 1 762 26.2 Pukehangi North 2 438 91.3 Pukehangi South 1 453 44.2 Mangakakahi 1 453 44.2 Fordlands 4 429 186.5 Koutu 1 342 58.5 Glenholme West 1 372 53.8 Total 18

3.8 Recurrence Rate

During 1998-2007 a total of 7 recurrences occurred yielding a recurrence rate of 12%. Reviewing the 5 year period prior to 1998 (1993-97) 3 initial presentations were identified which later recurred in the study period 1998-2007.The remaining 4 recurrences related to cases whose initial presentation had occurred during 1998- 2007. The recurrence rate of 12% was higher than the national average of 4.9% calculated by Jaine (1), but lower than the recurrence rate calculated previously by Loring (13). All recurrences occurred in those of Māori ethnicity. Two individuals experienced two recurrences each; the remaining 3 recurrences were the first recurrence for each of the 3 individuals involved.

Secondary prophylaxis data is not collected systematically by Lakes DHB. However, retrospective data collected monthly by RGPG indicate that between 48% and 85% of secondary prophylaxis antibiotic injections are successfully given within 5 days of the intended date.(19) However, the RGPG data covers only Rotorua District and not Taupo District.

4 Discussion

The purpose of this report was to describe the epidemiology of ARF in Lakes DHB during the period 1998-2007. This information may be used to direct strategies to reduce the incidence of ARF in Lakes DHB. This study successfully calculated the rates of ARF across gender, ethnic, and geographic variables. In conjunction with the recurrence rate, this information can be measured alongside existing local and national studies to compare Lakes DHB with other areas. Accordingly, successful interventions which have been described in the literature or have been delivered elsewhere may be applicable to the patterns of ARF seen in Lakes DHB.

A total of 77 cases of ARF presented to hospitals in Lakes DHB during the 1998- 2007 study period. However, only 58 of these were attributable to those usually resident in Lakes DHB; the remainder of the 19 cases came mainly from eastern settlements in Bay of Plenty DHB such as Murupara and Kawerau. The total of 58 cases from Lakes residents was similar to the 58 initial cases observed by Jaine during the slightly earlier period of 1996-2005.(1) The age standardised incidence rate of 5.6 per 100,000 compares with the 5.7 per 100,000 calculated by Jaine.(1) The incidence rate measured in this study supports Jaine’s ranking of Lakes DHB as the fourth highest among DHBs for ARF incidence (see Appendix 1).

The vast majority of cases presenting to Lakes DHB were from those of Māori ethnicity. 84.2% of cases overall and 84.5% within the 5-14 year age group were of Māori ethnicity. This compares with national data showing Māori make up 59.5% of all cases in the country.(1) The incidence of ARF among Lakes DHB Māori was significantly higher than the national rate for Māori calculated by Jaine (15.6 vs. 8 per 100,000) (p<0.05).(1) Additionally, Māori in Lakes DHB were 26 times more likely to be diagnosed with ARF than the NZEO group. On a national level Māori are ten times as likely to be diagnosed with ARF.(1) These findings indicate inequalities within Lakes DHB even greater than those seen at the national level. These findings add to other work identifying inequalities within Lakes DHB.(20)

Overall the 5-14 year age group experienced the highest incidence of ARF. This pattern is consistent with that seen nationally.(1) Most cases of ARF presented during the winter months. This finding has been noted in other studies which have

23 observed a greater incidence of ARF during winter along with a greater rate of post- Streptococcal glomerulonephritis during summer months.(21)

The Rotorua and Taupo Districts had different rates of ARF. The crude rate of ARF in the Taupo District of 1.9 per 100,000 was considerably lower than the 7.9 cases per 100,000 in the Rotorua District. As stated previously, both districts have high Māori populations (27% of Taupo District, 34% of Rotorua District at the 2006 New Zealand Census)(17) and so a higher number of diagnosed cases in the Taupo District could be expected than the 6 which were observed over the ten year study period. Assuming a similar incidence rate to the Rotorua District it is possible that 2 cases of ARF per year are not being diagnosed in the Taupo District. However, it may also be the case that Taupo has a lower real incidence of ARF. Further research may be required in the Taupo District to determine the rate of ARF in the area. This may include an audit of GP practices to identify any cases managed in general practice rather than referred to the hospital.

Over a 10 year study period rates of ARF for all age groups combined varied greatly between CAUs as shown in Appendix 3. The highest rates were 27.4 per 100,000 in Pukehangi North in the Rotorua District, and 31.9 per 100,000 in Rangatira Park in the Taupo District. Similarly, over the ten year period several CAUs in the Rotorua District had rates of ARF above 50 per 100,000 in the 5-14 year age group. Pukehangi North had the highest rate with 114 cases per 100,000 while Mangakakahi had a rate of 110 per 100,000; Fordlands had a rate of 93 per 100,000. The remaining high-rate CAUs were produced with only 1 or 2 cases over the 10 year study period and so these results should be viewed with care as a low number of cases in a small population can produce an apparently high rate.

Over a 5 year study period several CAUs in the Lakes DHB area had incidence rates in 5-14 year olds in excess of 50 per 100,000. However, the majority of CAUs had small numbers of cases and cannot be reliably used to indicate appropriate sites for population interventions such as a school-based throat swabbing campaign. An apparently high rate produced by only 1 or 2 cases could have been due to chance. Small populations of 5-14 year olds in these CAUs can also magnify the apparent rate of ARF. Fordlands however had 4 cases and could be considered as a site for targeted intervention. At a rate above 50 per 100,000 per year over a 5 year study period the most recent NHF guidelines recommend the consideration of primary prevention programmes in high risk populations.(18)

Case notifications to the Public Health Unit remained low throughout the decade studied. A peak of 4 notifications for the 12 cases diagnosed at Lakes DHB occurred in the year 1999. In contrast, no cases from 2001 were notified to the Public Health Unit despite 7 cases being discharged from Lakes DHB that year. Among the 58 cases usually resident in Lakes DHB only 19 were notified; a rate of 33%. This rate is lower than that previously calculated by Loring (approximately 50%) for BOPDHB and Lakes DHB.(13) It is also significantly lower than that calculated by Jaine (52%, p<0.05) using national notification and hospitalisation data.(13) These results indicate that notification data alone will not give an accurate picture of incidence rates within the DHB. This may change in the future as notification completeness improves. Consequently, hospital discharge data should be regularly reconciled against PHU notifications to gain an accurate understanding of ARF in the DHB.

The recurrence rate in Lakes DHB was significantly higher than the national average calculated by Jaine.(1) The Lakes recurrence rate of 12% was more than double the national rate of 4.9% (p<0.01).(1) On a positive note however, the recurrence rate was lower than the 21% previously calculated by Loring using a different study window and dataset.(13) Although the Lakes rate represents 7 cases of the total of 58, the figure denotes a lost opportunity for intervention, particularly given the undisputed effectiveness of penicillin in secondary prevention.(4)(22)(2, 23) These rates indicate the need for improved secondary prevention in Lakes DHB to reach the national average of 4.9%.(1)

A case register could improve secondary prevention in Lakes DHB.(8) A register could do this by listing those who require secondary prevention and the time at which medication is due. Alerts and notifications could be generated for District Nursing staff where medication is overdue. A register could be accessed by the multidisciplinary team involved in managing an individual, with regular progress reports generated for different team members. The use of registers to monitor cases has been promoted by the World Health Organization and ARF registers have been linked with lower recurrence rates.(24)

4.1 Limitations

This study has several limitations. First, the analyses were dependent on hospitalisation data over the past decade. This approach may not detect all cases of ARF during that time as some cases may have been managed solely in primary care, or the condition may not have been accurately diagnosed and referred to hospital. Under-diagnosis is also possible at the hospital level as ARF is based on a collection of clinical criteria. Furthermore, cases may not be assigned the correct ICD code once they are diagnosed.

It is possible that the rates of ARF calculated here are underestimates. This study used the 2006 New Zealand Census for population based calculations; however, a high population denominator will reduce the apparent rate of a condition. Similarly, misclassification of Māori ethnicity has been documented previously.(25)(26) This effect would reduce the rate of ARF among Māori whilst increasing rates among other ethnic groups. Finally, this study did not analyse admission data for other DHBs. Consequently, the incidence of ARF among Lakes DHB residents may be higher if some cases presented to hospitals outside Lakes DHB. However, if the actual rate of ARF in Lakes DHB differs from that calculated here the difference is likely to be small; Jaine’s recent study presented rates of ARF by domicile and produced similar overall age-standardised incidence to this study.(1)

5 Recommendations

This study has provided an updated picture of ARF in Lakes DHB. The overall rate of the condition is higher than the national average for all ethnic groups and for Māori. This disparity is even more obvious in the 5-14 year age group. Furthermore, the recurrence rate in Lakes DHB is more than double the national average. The condition is not distributed evenly among the population with Māori representing 84% of all cases and 100% of recurrences. A single CAU in the Rotorua District surpassed the NHF threshold for consideration of a targeted primary prevention programme with a robust number of cases.(18) Based on the findings of this study it would be beneficial for Lakes DHB to consider several recommendations to reduce the incidence of ARF. Because of similar issues, some of these recommendations mirror those already proposed by Loring(13). It is recommended that:

1. Lakes DHB and Toi te Ora take a community-level approach to interventions aimed at reducing the incidence of ARF. Only 1 CAU (Fordlands) convincingly meets the threshold for consideration of a targeted primary prevention programme. This differs from the pattern seen in BOPDHB where specific well circumscribed communities such as Kawerau and Opotiki had a high number of cases in addition to a high incidence rate. These community level interventions should focus on the modifiable risk factors which are linked to ARF and which are mediated through the effects of poverty; these include household crowding, poor nutrition, smoking, and second hand smoke exposure among children. This approach will require Lakes DHB and Toi te Ora to work with local and central government, Housing New Zealand, and Work and Income New Zealand to address these issues. Particular focus on these issues for Māori and those with young children is recommended.

2. Lakes DHB and Toi te Ora work to improve the likelihood of those with streptococcal pharyngitis seeking treatment. This can be achieved by facilitating the delivery of health promotion and health education activities in high risk communities which educate children, parents, and teachers of the need for medical review when a throat infection develops. Information on the importance of completing a course of antibiotics should also be included in health promotion activities. This recommendation requires re-educating the public on the appropriateness of antibiotics for specific throat infections.

3. Lakes DHB and Toi te Ora work to improve the ability of primary care providers to be aware of, diagnose, and treat streptococcal pharyngitis. This can be achieved by facilitating the delivery of health education and professional development for primary care providers. The difficulty of diagnosing streptococcal pharyngitis and ARF has been noted in other research(8), and clinicians’ sensitivity to detection is limited by seeing the condition infrequently. Education could be provided through continuing medical education sessions and printed or electronic information for primary care providers.

4. Lakes DHB work to improve access to primary healthcare by facilitating free general practitioner (GP) visits in the high risk 5-14 year age group in high risk communities. This would remove the access barrier of cost particularly

among those in low socioeconomic groups who are most affected by this condition (50% of Māori occupy the three most deprived decile groups).(27) In addition, Lakes DHB should fully subsidise the cost of a 10 day course of oral penicillin for streptococcal pharyngitis. Previous research has demonstrated the increased utilisation achieved when cost barriers to access are removed from primary care.(28)

5. Lakes DHB and Toi te Ora reduce ARF recurrence rates by developing a rheumatic fever register. This approach is advocated by the World Health Organization and the NHF.(18)(8) A register would serve as a database of those who have been diagnosed with ARF and requiring secondary prophylaxis. A register could alert relevant personnel when medication is overdue and would facilitate improved monitoring of the success of secondary prophylaxis. A register would help to identify those with least compliance to the secondary prevention regimen.

6. Lakes DHB and Toi te Ora work to increase ARF case notifications from secondary care by facilitating education for paediatric staff on the detection, management, and notification of ARF along with providing information on the epidemiology of the condition in Lakes DHB. In conjunction, Toi te Ora can provide ongoing quarterly feedback to clinicians on the number of cases notified in an effort to capture any which have been missed.

7. Lakes DHB and Toi te Ora monitor the impact of these recommendations by half-yearly measurements of the number of initial and recurrent cases of ARF discharged from Lakes DHB, the number of cases notified, and the number of cases given secondary prophylaxis within the desired timeframe. This information could be summarised for key personnel in Lakes DHB and Toi te Ora. Regular feedback would allow adjustments to the strategies outlined here and the development of new approaches where the incidence of ARF is not reducing.

Appendix 1 DHB comparison of age-standardised ARF incidence 1996Rate-2005. Based on data from Jaine.(1)

Hutt Lakes Otago Auckland Waikato Taranaki Tairawhiti Northland Wairarapa Midcentral Southland Waitemata Whanganui Canterbury West Coast Bay ofHawke's Plenty Bay South Canterbury Counties Manukau Capital and Coast Nelson/Marlborough

Appendix 2 Rates of ARF in selected areas of BOPDHB and Lakes DHB.

Table 5 Age specific (5-14 years) incidence rates of ARF by TLA and DHB 2003-7.(13)

Table 6 Age-specific (5-14 years) annual incidence rates of ARF by selected Census Area Unit 2003-7 (13)

Values calculated for the Fordlands CAU (Rotorua District) over 5 years are listed below for comparison. These values are also found in Table 4. Area No. of cases 5-14 Incidence Population aged years /100,000 5-14 years Fordlands 4 186.5 429

Appendix 3 Incidence rates (per 100,000 per year) in selected age and ethnic groups in various census area units for Lakes DHB residents 1998-2007. Cells shaded red indicate incidence greater than 50/100,000/yr

All Age Groups 5-14 Year Age Group All Cases in All Cases in Rate Rate Rate Rate CAU Cases Māori Cases Māori Fairy Springs 1 5.0 1 10.5 1 28.7 1 44.4 Fenton 1 7.2 ------Fordlands 4 21.0 3 25.6 4 93.2 3 102.0 Glenholme 1 4.4 0.0 1 26.9 - - West Hamurana 1 4.2 1 33.7 - - - - Hillcrest 1 6.2 1 17.4 - - - - Kaingaroa 1 20.6 1 25.4 1 85.5 1 101.0 Forest Kawaha Point 1 6.1 1 22.2 1 35.5 1 98.0 Koutu 4 21.1 4 33.0 2 58.5 2 77.5

Kuirau 3 27.0 3 77.5 1 98.0 1 175.4 Mangakakahi 5 20.4 5 48.6 5 110.4 5 193.8 Ngapuna 1 19.5 1 29.2 1 101.0 1 138.9 Ngongotaha 3 10.4 3 26.8 1 19.7 1 34.4 North

Owhata East 3 14.1 3 34.4 3 78.7 3 135.1 RotoruaDistrict Owhata West 3 8.4 1 6.2 2 29.1 - - Pukehangi 6 27.4 5 42.7 5 114.2 5 170.1 North Pukehangi 1 3.6 1 14.4 1 22.1 1 61.7 South Selwyn Heights 2 17.7 2 33.8 1 40.2 1 62.9 Springfield 1 2.3 1 16.3 1 16.4 1 83.3 Tikitere 1 3.5 1 8.5 1 19.4 1 34.4 Utuhina 1 7.1 1 22.2 - - - - Victoria 2 12.1 2 41.9 - - - - Western 5 13.1 3 15.9 2 26.2 1 21.2 Heights Hilltop 1 2.8 1 17.5 1 18.6 1 75.8 Rangatira Park 2 31.9 2 303.0 - - - - Tauhara 1 2.3 1 6.4 1 14.0 1 26.9 Turangi 1 3.1 1 5.6 1 18.9 1 24.0

Taupo Taupo District Waipahihi 1 5.7 0.0 1 45.0 - - Grand Total 58 49 38 32

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