Estimating AIDS-free survival in a severely immunosuppressed asymptomatic HIV-infected population in the era of antiretroviral triple combination therapy. Swiss HIV Cohort Study.

Background: Antiretroviral triple combination therapies have been evaluated in randomized controlled trials and cohort studies. Little is known about their impact on asymptomatic, severely immunosuppressed, HIV-infected individuals in a real world population.

Objectives: To describe disease progression in a broad asymptomatic population of HIV-infected individuals with a CD4 count <100 cells/mm3 before and after the introduction of combination triple therapy.

Design: Six-month homogenous Markov chain consisting of four recurrent AIDS-free states and one absorbing AIDS state: (1) CD4 count > or =100 cells/mm3, (2) CD4 count 75 to 99 cells/mm3, (3) CD4 count 50 to 74 cells/mm3, (4) CD4 count 0 to 49 cells/mm3, and AIDS.

Setting: Swiss HIV Cohort Study database.

Patients: A total of 1027 patients contributed to 2634 pairs of 6-month observations from 1993 to 1995, and 681 patients contributed to 2077 pairs of 6-month observations from 1996 to 1997.

Measurement: AIDS-free survival probabilities and the expected AIDS-free survival time.

Results: The expected number of AIDS-free months in a 3-year period was 17 (95% confidence interval [CI], 16-19) for patients starting in state 4 prior to 1996 versus 26 months (95% CI, 24-28) for patients starting in state 4 after 1996. For these two time periods, the corresponding expected numbers of AIDS-free months were 21 (95% CI, 20-22) versus 30 (95% CI, 28-32) for state 3 and 23 (95% CI, 21-24) versus 33 (95% CI, 32-34) for state 2.

Conclusion: Expected 3-year AIDS-free survival in severely immunosuppressed individuals with CD4 counts <100 cells/mm3 improved significantly between 1993 to 1995 and 1996 to 1997.