AIDS-related opportunistic illnesses occurring after initiation of potent antiretroviral therapy - The Swiss HIV Cohort Study

Context Acquired immunodeficiency syndrome-related opportunistic illnesses (Ols) continue to occur after initiation of potent antiretroviral therapy i n patients with human immunodeficiency virus (HIV) infection, Risk factors for clinical progression to Ols during potent therapy are not well defined, Objective To examine the incidence of and risk factors for Ols among patien ts treated with potent antiretroviral therapy in a population-based study, Design The Swiss HIV Cohort Study, a prospective cohort study of adult HIV- infected persons. Setting Seven study centers throughout Switzerland. Patients A total of 2410 cohort study participants with a potential follow- up of at least 15 months after starting potent therapy between September 19 95 and December 1997. Main Outcome Measures Disease-specific incidence of Ols during the 6 months preceding potent antiretroviral therapy and at 3 intervals after initiatin g therapy; risk factors for development of Ols during therapy. Results Of the 2410 participants, 143 developed 186 Ols after initiation of potent antiretroviral therapy, Incidence of any OI decreased from 15.1 per 100 person-years in the 6 months before therapy to 7.7 in the first 3 mont hs after starting treatment, 2.6 in the following 6 months, and 2.2 per 100 person-years between 9 and 15 months. Reductions in incidence ranged from 38% per month for Kaposi sarcoma (P<.001) to 5% per month for non-Hodgkin l ymphoma (P =.31). Baseline CD4 cell count continued to predict the risk of disease progression after initiating potent therapy, Compared with CD4 cell counts above 200 x 10(6)/L, the hazard ratio for developing Ols was 2.5 (9 5% confidence interval [CI], 1.4-4.5) for counts between 51 and 200 x 10(6) /L and 5.8 (95% CI, 3.2-10.5) for counts below 51 x 10(6)/L at baseline, In dependent of baseline CD4 cell count, a rise in CD4 cell count by 50 x 10(6 )/L or more and undetectable HIV-1 RNA in plasma (<400 copies/mL) by 6 mont hs reduced risk of subsequent events, with hazard ratios of 0.32 (95% CI, 0 .20-0.52) and 0.39 (0.24-0.65), respectively, Conclusions Our data indicate that the risk of developing an OI for a perso n receiving potent antiretroviral therapy is highest during the initial mon ths of therapy, Baseline CD4 cell count and immunologic and virologic respo nse to treatment were strong predictors of disease progression in patients receiving potent therapy. Individuals with CD4 cell counts of 50 x 10(6)/L or below may need close clinical surveillance after initiation of potent th erapy.