DETERMINANTS OF PROGRESSION TO AIDS IN HIV-INFECTED INDIVIDUALS - AN UPDATE FROM THE ITALIAN SEROCONVERSION STUDY

The Italian Seroconversion Study (ISS) involves 16 major HIV-treatment centers across Italy and about 1,200 individuals. These individuals w ere HIV-negative less than 2 years before the first positive test and seroconverted between 1980 and 1994. The majority were infected throug h i.v. drug use (56%), male-to-male sex (25%), and heterosexual contac t (7%). For each end point, crude and adjusted relative hazards were c alculated using standard survival techniques such as Kaplan-Meier curv es, log-rank test, and Cox proportional hazards regression models. Aut oregression models were used to describe CD4 cell reductions. Objectiv es were as follows: to estimate HIV disease progression rates; to asse ss whether there are differences in the rate of development of severe immunosuppression, AIDS, and death according to age, gender, and expos ure category; to identify co-factors and predictors of disease pro gre ssion; and to evaluate the clinic-based population ''effect'' of antir etroviral treatment. The risk for developing AIDS among individuals in the ISS cohort was less than 50% by 10 years after HIV seroconversion . Using univariate analysis, more rapid progression was found for olde r individuals than for younger individuals and for homosexual men comp ared with those in other exposure categories. No difference between me n and women was observed. After adjusting for age, differences among e xposure groups disappeared. Individuals with a history of acute HIV di sease were more likely to develop AIDS than other seroconverters. Co-i nfection with HCV and HTLV-II did not accelerate progression to AIDS. The cumulative incidence of receiving pre-AIDS therapy within 7 years of seroconversion was 49.2% (95% CI 45.3-53.0). The relative hazards o f developing AIDS in patients who started treatment with zidovudine (A ZT) monotherapy was 0.57 (0.36-0.91) and 0.92 (0.64-1.33) within the f irst year and after 1 year from AZT initiation, respectively. The effe ct was greater among homosexual men than among i.v. drug users. In con clusion, incident cohort studies may provide accurate information on i ncubation time and co-factors for disease progression. Observational s tudies may also provide useful information about the effect of treatme nt at the community level, which may complement the results of clinica l trials.