Differences in time from HIV seroconversion to CD4+ lymphocyte end-points and AIDS in cohorts of homosexual men

Objective To evaluate the decline in CD4+ counts in relation to the incidence of AIDS in different cohorts of homosexual men and to quantify possible consequences of laboratory variation in CD4+ measurement. Methods Our study includes 403 men with well documented dates of HIV seroconversion originating from five cohort studies among homosexual men. Differences in time from HIV seroconversion to the first CD4+ count dropping <500 or 200 $$ 10⁶/l and to AIDS were evaluated using Kaplan-Meier survival analyses. Results We found considerable differences between cohorts in CD4+ depletion, but not in the incidence of AIDS (1987 definition). Conclusions Variation in CD4+ depletion appears to be mainly the result of laboratory differences. Policy recommendations on a basis of CD4+ counts probably requires a calibration of measurement. The 1993 AIDS case definition leads to a site-specific shortening of the incubation time, which complicates the study of the natural history of HIV infection and of trends in the AIDS epidemic.