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.
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).
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 106/l according to the calendar year of seroconversion in the Italian Seroconversion Study was assessed using different censoring strategies.
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.
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. (...)
Mots-clés Pascal : SIDA, Virose, Infection, Etude cohorte, Echantillon censuré, Etude statistique, Interprétation, Evolution, Pronostic, Biais méthodologique, Simulation, Epidémiologie, Méthode, Etude critique, Immunopathologie, Immunodéficit, Statistique, seroconversion
Mots-clés Pascal anglais : AIDS, Viral disease, Infection, Cohort study, Censored sample, Statistical study, Interpretation, Evolution, Prognosis, Methodological bias, Simulation, Epidemiology, Method, Critical study, Immunopathology, Immune deficiency, Statistics
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 98-0394059
Code Inist : 002B05C02D. Création : 25/01/1999.