Acquired Immunodeficiency Syndrome (AIDS)-free time after Human Immunodeficiency Virus type 1 (HIV-1) seroconversion in homosexual men

To estimate the time interval between human immunodeficiency virus type 1 (HIV-1) seroconversion and acquired immunodeficiency syndrome (AIDS) diagnosis in homosexual men, prospective incident cohorts are difficult to obtain and, if assembled, provide few events owing to the long incubation time. Although seroprevalent cohorts are numerous in size and events, the information is limlted due to the unknown times since seroconversion. To combine the information provided by 1,628 seroprevalent men (304 AlDS cases) and 233 seroconverters (12 AlDS cases) belng followed in a multicenter study since 1984, the postseroconversion changes in hematologk variables occurring in the incident cohort were used to develop a model thet allowed for the imputation of the unknown times since seroconversion for the seroprevalent cohort Nonparametric life table methods incorporating truncation and censoring were applied for the estimation of the probability distribution of the AIDS-free time after seroconversion. The precision of the estimates was evaluated using bootstrap methods. The analysis suggested that AlDS is unlikely (<O.5%) in the first year; 78% of seropositive homosexual men remain AIDS-free 60 months after seroconversion; and the AlDS incidence increases for months 12-36 and levels off at 38 per 1,000 personsemesters for months 42-60. The nonparametric estimate of the incidence rate suggests a median AIDS-free time of 11 years, which is longer than previous estimates based on parametric models.