Natural history of HIV infection in the era of combination antiretroviral therapy

Background: The use of protease inhibitor-containing (PI) combination antiretroviral therapy has led to a reduction in the incidence of opportunistic illness and mortality (events) in HIV infection. We wished to quantify the changing incidence of these events in our clinical practice and delineate the relationship between CD4, HIV-1 RNA, and development of events in patients receiving PI combination therapy. Methods: We assessed HIV-infected patients with CD4 counts less than or equal to 500 cells x 10(6)/l. We calculated the incidence of events from 1994 through 1998 and analyzed the association of temporal changes in event incidence and use of antiretroviral therapy. In patients on PI combination therapy, we determined the probability of achieving and maintaining an undetectable HIV-1 RNA response and determined the association of CD4, HIV-1 RNA, and developing an event. Results: The incidence of opportunistic illness declined from 23.7 events/100 person-years in 1994 to 14.0 events/100 person-years in 1998 (P < 0.001). Mortality declined from 20.2 deaths/100 person-years in 1994 to 8.4 deaths/100 person-years in 1998 (P < 0.001). Use of PI combination therapy was associated with a relative rate of opportunistic illness or death of 0.66 [95% confidence interval (CI), 0.51-0.85; P < 0.001]. The relative incidence of each of 16 opportunistic illnesses was approximately the same in 1998 as in 1994 except for lymphoma, cervical cancer and wasting syndrome which do not appeared to have declined in incidence. Approximately 60% of patients who received PI therapy achieved an undetectable HIV-1 RNA, and 65% of these patients maintained durable suppression of HIV-1 RNA. Achieving an undetectable HIV-1 RNA was associated with a decreased risk of an event, and was the variable most strongly associated with an increase in CD4 level. By multivariate analysis, the concurrent CD4 level was most strongly associated with developing an event. Conclusions: We observed a significant decline in the incidence of opportunistic illness and death from 1994 through 1998 associated with combination antiretroviral therapy. Patients who develop events while being treated with PI combination therapy were not likely to have achieved an undetectable HIV-1 RNA and are likely to have a low concurrent CD4 level. (C) 1999 Lippincott Williams & Wilkins.