AIDS-defining opportunistic illnesses in US patients, 1994-2007: a cohort study.

Objectives: To assess the incidence and spectrum of AIDS-defining opportunistic illnesses in the highly active antiretroviral therapy (cART) era.
Design: A prospective cohort study of 8070 participants in the HIV Outpatient Study at 12 U.S. HIV clinics.
Methods: We calculated incidence rates per 1000 person-years of observation for the first opportunistic infection, first opportunistic malignancy, and first occurrence of each individual opportunistic illness during 1994-2007. Using stratified Poisson regression models, and adjusting for sex, race, and HIV risk category, we modeled annual percentage changes in opportunistic illness incidence rates by calendar period.
Results: Eight thousand and seventy patients (baseline median age 38 years; median CD4 cell count 298 cells/microl) experienced 2027 incident opportunistic illnesses during a median of 2.9 years of observation. During 1994-1997, 1998-2002, and 2003-2007, respectively, rates of opportunistic infections (per 1000 person-years) were 89.0, 25.2 and 13.3 and rates of opportunistic malignancies were 23.4, 5.8 and 3.0 (P for trend <0.001 for both). Opportunistic illness rate decreases were similar for the subset of patients receiving cART. During 2003-2007, there were no significant changes in annual rates of opportunistic infections or opportunistic malignancies; the leading opportunistic illnesses (rate per 1000 person-years) were esophageal candidiasis (5.2), Pneumocystis pneumonia (3.9), cervical cancer (3.5), Mycobacterium avium complex infection (2.5), and cytomegalovirus disease (1.8); 36% opportunistic illness events occurred at CD4 cell counts at least 200 cells/microl.
Conclusions: Opportunistic illness rates declined precipitously after introduction of cART and stabilized at low levels during 2003-2007. In this contemporary cART era, a third of opportunistic illnesses were diagnosed at CD4 cell counts at least 200 cells/microl.