Impact of combination antiretroviral therapy on the risk of tuberculosis among persons with HIV infection

Objective: To assess the association between use of different antiretroviral regimens and incidence of tuberculosis among HIV-infected individuals. Design: Observational, multicenter, prospective cohort study. Setting and patients: Twenty-eight infectious diseases hospital units in Italy. A total of 2160 HIV-infected persons were considered for enrolment in a study on the implementation of tuberculosis preventive therapy between 1 May 1995 and 30 April 1996. The 1360 subjects who completed tuberculin screening at base-line were included in this analysis. Information on the use of antiretroviral therapies over time was collected. The median duration of follow-up was 104 weeks and 997 subjects (73.3%) completed the study. Main outcome measure: Incidence of active tuberculosis according to different types of antiretroviral therapy. Results: Eighteen cases of tuberculosis were observed with an overall incidence rate of 0.79 per 100 person-years of observation [95% confidence interval (Cl), 0.51-1.31]. Tuberculin positivity and low CD4+ lymphocyte count were the only base-line variables independently associated with the risk of tuberculosis. During follow-up, 637 patients took double combination antiretroviral therapy and 387 took triple combination therapy. After adjusting for base-line characteristics of enrolled individuals, the relative hazard of tuberculosis was 0.16 (95% Cl, 0.03-0.74) for double combination therapy and 0.08 (95% Cl, 0.01-0.88) for triple combination therapy compared with no therapy or monotherapy. Conclusions: Combination antiretroviral therapy significantly reduced the risk of tuberculosis in HIV-infected persons. In industrialized countries, the widespread use of this treatment may determine a decrease in the incidence of HIV-associated tuberculosis, possibly contributing to a reduction in the overall incidence of tuberculosis.