Evaluating the effect of year of seroconversion on HIV progression in cohort studies. Italian Seroconversion Study.

Important note: Information in this article was accurate in 1999. The state of the art may have changed since the publication date.

Evaluating the effect of year of seroconversion on HIV progression in cohort studies. Italian Seroconversion Study.

AIDS. 1998 Jul 30;12(11):1353-60. Unique Identifier : AIDSLINE MED/98372121
Cozzi Lepri A; Phillips AN; Pezzotti P; Mocroft A; Sabin CA; Porter K; Rezza G; Royal Free Centre for HIV Medicine and Department of Primary Care; and Population Sciences, Royal Free and University Medical; School, University College London, UK.

Abstract: OBJECTIVES: To show how a spurious association between the calendar year of seroconversion and HIV progression arises as a result of censoring the follow-up of individuals at their last visit, when the individuals' visits are intermittent. DESIGN: A notional cohort of 1140 seroconverters and a cohort study of 1270 HIV-infected individuals seroconverted between 1985 and 1994, and followed up to December 1995 (the Italian Seroconversion Study cohort). METHODS: Failure times and rate of the patients attending the clinic over the study period were simulated for the notional cohort. Three separate scenarios with different probabilities of making a visit were considered. Standard survival analysis techniques were used to assess the effect of the year of seroconversion on HIV progression. The progression to a CD4 cell count of 200 x 10(6)/l according to the calendar year of seroconversion in the Italian Seroconversion Study was assessed using different censoring strategies. RESULTS: A spurious effect of the year of seroconversion consistently appeared in 100 repeated simulations. When ignoring the visits occurring after the first year of follow-up in the Italian Seroconversion Study cohort, results supported the hypothesis of no effect of the year from seroconversion. CONCLUSIONS: The choice of the censoring strategy is crucial when assessing the effect of year of seroconversion using survival analysis in cohort studies with intermittent visit structure. Different censoring strategies should be considered before firmly concluding that more virulent strains or the use of treatment are modifying the natural history of HIV disease from cohort studies of this nature.

Keywords: JOURNAL ARTICLE Cohort Studies Disease Progression Follow-Up Studies Human HIV Seropositivity/IMMUNOLOGY/*PHYSIOPATHOLOGY Italy Models, Biological Support, Non-U.S. Gov't Time Factors
990130
A9911057

AEGiS is a 501(c)3, not-for-profit, tax-exempt, educational corporation. AEGiS is made possible through unrestricted funding from Boehringer Ingelheim, Bridgestone/Firestone Charitable Trust, Bristol-Myers Squibb Company, Elton John AIDS Foundation, Gill Foundation, the National Library of Medicine, Quest Diagnostics, Roche and Trimeris, and donations from users like you. Always watch for outdated information. This article first appeared in 1999. This material is designed to support, not replace, the relationship that exists between you and your doctor.

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 1999. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .