Impact of highly active antiretroviral therapy on individual AIDS-defining illness incidence and survival in Australia

OBJECTIVE: To determine the effect of highly active antiretroviral therapy (HAART) on incidence of initial AIDS-defining illnesses (ADIs) and survival after individual ADIs. METHODS: Australian AIDS notification data over the period 1993 to 2000 were examined. Analyses were based on all initial ADIs. To examine the impact of HAART, two periods of AIDS diagnosis were chosen: pre-HAART (1993-1995) and HAART (1996-2000). Comparisons between these two periods included proportion of individual ADIs, median CD4 lymphocyte counts at and survival following AIDS and individual ADIs. Median survival was based on Kaplan-Meier estimates, with examination of factors influencing survival in a Cox proportional hazards model. RESULTS: Over the period 1993 to 2000 in Australia, 5017 initial ADIs were diagnosed among 4351 AIDS cases. At AIDS diagnosis, changes from the pre-HAART (1993-1995) to HAART (1996-2000) periods included an increased proportion of Pneumocystis carinii pneumonia (PCP) (25.9% to 30.4%; p =.001), AIDS dementia complex (5.2% to 6.8%; p = 0.029), non-Hodgkin lymphoma (NHL) (4.4% to 6.3%; p =.005), and tuberculosis (0.5% to 2.7%; p <.0005). Median survival following AIDS increased from 19.6 months for AIDS cases diagnosed in 1993 to 1995 to 39.6 months for AIDS cases diagnosed in 1996 to 2000 (p <.0005). Median survival was stable for NHL (7.5-8.8 months; p =.26), but increased significantly for almost all other ADIs. CONCLUSIONS: An increased proportion of PCP relative to other ADIs suggests an increasing proportion of AIDS patients not receiving specific prophylaxis, presumably because of "late" HIV diagnosis. Survival following almost all ADIs has increased in the era of HAART, although the prognosis after NHL remains extremely poor.