Background: Active tuberculosis is common among human immunodeficiency virus (HIV)-infected persons living in tuberculosis-endemic areas, but the hazard of subsequent tuberculosis disease has not been quantified in a single prospective cohort.
Methods: Among HIV-infected, BCG-immunized adults with CD4 counts ≥200 cells/μL who received placebo in the DarDar tuberculosis vaccine trial in Tanzania, we compared the prospective risk of active tuberculosis between subjects who did and who did not report prior active tuberculosis. All subjects with a positive tuberculin skin test without prior active tuberculosis were offered isoniazid preventive treatment. Definite or probable tuberculosis was diagnosed during active follow-up using rigorous published criteria.
Results: We diagnosed 52 cases of definite and 92 cases of definite/probable tuberculosis among 979 subjects during a median follow-up of 3.2 years. Among the 80 subjects who reported prior active tuberculosis, 11 (13.8%) subsequently developed definite tuberculosis and 17 (21.3%) developed definite/probable tuberculosis, compared with 41 (4.6%) and 75 (8.3%), respectively, of 899 subjects without prior active tuberculosis (definite tuberculosis risk ratio [RR], 3.01; 95% confidence interval [CI], 1.61-5.63, P < .001; definite/probable tuberculosis RR, 2.55; 95% CI, 1.59-4.09, P < .001). In a Cox regression model adjusting for age, CD4 count, and isoniazid receipt, subjects with prior active tuberculosis had substantially greater hazard of subsequent definite tuberculosis (hazard radio [HR], 3.69; 95% CI, 1.79-7.63, P < .001) and definite/probable tuberculosis (HR, 2.78; 95% CI, 1.58-4.87, P < .001).
Conclusions: Compared to subjects without prior tuberculosis, the hazard of active tuberculosis is increased 3-fold among HIV-infected adults with prior active tuberculosis. Clinical Trials Registration. NCT0052195.
Trial registration: ClinicalTrials.gov NCT00052195.