The UK Register of HIV Seroconverters: Estimating the Times from HIV Seroconversion to the Development of Aids and Death and Associated Factors from a Cohort of HIV Seroconverters
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The UK Register of HIV Seroconverters: estimating the times from HIV seroconversion to the development of AIDS and death and associated factors from a cohort of HIV seroconverters This work is presented as a thesis for the degree of DOCTOR OF PHILOSOPHY in Epidemiology at the Faculty of Clinical Sciences by Kholoud Porter From the Medical Research Council HIV Clinical Trials Centre University College London Medical School The Mortimer Market Centre March 1998 ProQuest Number: U642762 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest U642762 Published by ProQuest LLC(2015). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT Knowledge of the distribution of intervals from HIV infection to the development of AIDS and to death, and the factors affecting these intervals is vital to an understanding of the natural history of HIV infection and for making projections of future numbers of AIDS cases. This distribution may have changed since the beginning of the epidemic due particularly to the introduction of anti-retroviral treatment and prophylaxis for Pneumocystis carinii pneumonia. It is likely to be influenced by new advances in the management of HIV infected individuals in the future. Changes in the incubation period distribution could also occur in the absence of changes in available treatments and treatment uptake, due to the evolving distributions of new viral strains. It is therefore important to monitor whether there are changes in the incubation period distribution and, if so, the extent of those changes and factors associated with them. A number of studies have provided estimates for this period in different population groups. Most have tended to focus on one transmission category, e.g. homosexual men, injecting drug users, or haemophiliacs; are small in size; or are no longer recruiting new subjects. This thesis reports on the design, methods and findings from a register of HIV-infected individuals in the UK in whom the date of seroconversion is known with reasonable precision (seroconverters). Baseline and annual follow up information is collected and includes: sex, age, ethnic group, route of HIV transmission, latest CD4 count, details of therapy and prophylaxis, AIDS defining events and vital status. Findings presented in this work are on 2022 seroconverters reported by the end of September 1997, the first 3 years of the Register. Careful documentation of the time that each seroconverter came under unbiased follow up for the purposes of the Register was made so as to minimise any bias resulting from the preferential inclusion of long-term non-progressors and recent seroconverters. Censoring at the end of June 1995, the estimated median time to AIDS from HIV seroconversion was 9.26 years (95% CI= 8.46- 10.39). Censoring at the end of December 1996 the estimated median time from seroconversion to death (from any cause) was 10.79 years (95% CI= 9.81- 11.36 years). Age was found to be highly associated with disease progression with a relative risk of 1.43 (95% CI= 1.19- 1.71) and 1.51 (95% CI= 1.29- 1.78) for each 10-year increase in age to AIDS and death respectively. After adjustment for the effects of other covariates, no evidence of a difference was found between exposure categories, sex or over calendar time. ACKNOWLEDGEMENTS This work was undertaken while I was employed at the MRC HIV Clinical Trials Centre as Project Co-ordinator for the UK Register of HIV Seroconverters. It was never as a one-woman-band and I am deeply indebted to the many friends and colleagues without whose help, support, encouragement and example I could not have completed this work. I would especially like to thank Professor Anne Johnson and Professor Andrew Phillips whom I have been fortunate to have as my supervisors. I am extremely grateful to them for always finding time through their busy schedules to give guidance, encouragement and support, and always with patience and good humour. I am extremely grateful to Professor Janet Darbyshire for her endless support and encouragement throughout my work and study. I am especially thankful to her for being such an approachable and thoughtful person. I am most indebted to Dr Noël Gill for his guidance over many years and for his faith in my abilities. I am particularly indebted to him for arranging CDSC’s funding of this doctorate. So many colleagues at CDSC, SCIEH and the Trials Centre have helped make my job less stressful and more manageable and the goals more achievable. I should like to express my gratitude to them all and in particular: CDSC: Dr Barry Evans, Miss Amanda Wright, Mr Dominic Howitt, Dr Ruth Gilbert, Ms Anna Molesworth, and Mrs Pauline Kaye. SCIEH: Dr David Goldberg, Mr Glen Codere, and Ms Geraldine Bums. Clinical Trials Centre: Ms Charlotte Duff, Ms Joanne Gillett, Mr Patrick Kelleher, Ms Sarah Walker, Dr Abdel Babiker, Dr Malcolm Hooker, Mr Adrian Kimberley, and Mr Robert Manning. This work would not have been possible without the help of clinicians, nurses, database administrators, microbiologists and virologists in a number of centres throughout the United Kingdom. I am very grateful to each of them for their continued help and support. Their names appear in Appendix II to this work. 3 Last, and certainly not least, a special thank you to Tariq and Adam for being the constant source of moral support. CONTENTS Page List of tables 6 List of figures 9 Chapter I Introduction 11 Chapter II A review of publications of HIV seroconverter cohorts 30 Chapter III Methods 68 Chapter IV Methodological issues 81 Chapter V Characteristics of the UK Register cohort 98 Chapter VI Statistical methods and an evaluation of bias 118 Chapter VII Progression estimates from HIV seroconversion to 131 AIDS and to death Chapter VIII A summary of findings and further work 153 APPENDICES 165 I Members of the Executive and Steering committees II Names of collaborators III Definition of an acute seroconverter IV Data collection forms V Time of entry into risk set for each clinical centre VI Epidemiology & Infection publication REFERENCES 189 LIST OF TABLES Table Title Page 1.1 Summary of the 1986 classification system for the clinical 15 manifestations of HIV infection 1.2 Summary of the 1993 classification system for the clinical 16 manifestations of HIV infection 1.3 Diseases included in the current definition for AIDS 18 1.4 Definitive Diagnostic Methods for Diseases Indicative of AIDS 19 1.5 Presumptive Methods for Diseases Indicative of AIDS 20 1.6 AIDS cases and HIV infection reports in the UK: data reported to 22 CDSC and SCIEH to the end of September 1994 1.7 Drugs prescribed in HIV infection 27 2.1 A summary of published studies of HIV progression rates in cohorts of 33 homosexual and bisexual men 2.2 A summary of published studies of HIV progression rates in cohorts of 44 persons with haemophilia 2.3 Estimates of progression to AIDS by age group at seroconversion from 46 the UKHCDO data 2.4 Estimates of progression to AIDS within 9 years of seroconversion by 46 age group for persons in the MCHS 2.5 A summary of published studies of blood transfusion recipients 49 2.6 Progression to AIDS by age group at seroconversion for Swedish 53 transfusion recipients 2.7 A summary of published studies of injecting drug users 55 2.8 A comparison of progression rates to AIDS between haemophiliacs in 61 Western Pennsylvania and homosexual men in the SFCC 2.9 A comparison of progression rates to AIDS between haemophiliacs in 61 MCHS and homosexual men in the 1RS 2.10 Progression rates to AIDS in haemophiliacs and transfusion recipients 64 in Sweden 4.1 Exposure category distribution of seroconverters, reported AIDS cases 83 and HIV infections (to the end of September 1994) and estimated prevalence (at the end of 1993) 4.2 Late entry: number of patients recruited from each of 3 hypothetical 90 clinics 4.3 Late entry: life table of retrospectively identified seroconverters from 90 hypothetical clinics A, B, and C (see Table 4.2) 4.4 Reporting delay for UK AIDS cases reported to CDSC and SCIEH to the 95 end of 1996 5.1 Characteristics of all subjects reported to the Register 100 October 1994 - September 1997 5.2 Total number of all subjects reported, number of AIDS diagnoses, and 104 number of deaths known by 30 September 1997 5.3 Age distribution of all subjects reported to the Register 105 by exposure category 5.4 Age at seroconversion of all subjects reported to the Register by 106 exposure category and sex 5.5 Interval between last negative and first positive HIV antibody tests and 109 proportions with AIDS and who have died 5.6 AIDS cases: Year of diagnosis of AIDS 110 5.7 AIDS cases: AIDS defining diseases and proportion of total diagnoses 112 5.8 AIDS cases: exposure category distribution of all AIDS-defining 113 conditions 5.9 Non-progressors: year of last clinic visit for persons not diagnosed 114 with AIDS 5.10 Deaths : Estimated year of seroconversion by year of death 115 5.11 Persons remaining alive in HIV survival estimates: year last known to 117 be alive 6.1 Documentation of seroconversion