Risk Factors for Developing Tuberculosis in HIV-1-infected Adults from Communities with a Low or Very High Incidence of Tuberculosis

Objective: To estimate the incidence rate of tuberculosis in HIV-1-infected adults resident in a region with a high tuberculosis prevalence and to identify clinical and laboratory parameters associated with increased risk of developing tuberculosis.

Methods: Adult patients going to the University of Cape Town HIV clinics between January 1986 and May 1996. The following variables were assessed for the risk of developing tuberculosis: ethnicity, employment and education status, World Health Organization (WHO) clinical stage, erythrocyte sedimentation rate (ESR), CD4+ count, and total lymphocyte count. Tuberculin skin test data were not available.

Results: There were 198 prevalent and 144 incident cases of tuberculosis in the cohort of 1206 patients. The incidence rate of tuberculosis risk was 10.4/100 person years. WHO clinical stages 3 and 4 (risk ratio [RR], 3.4; 95% confidence interval [CI], 1.8-6.4), ESR >75 mm/hour (RR, 3.5; CI, 1.8-6.5) and being a member of a high-prevalence tuberculosis community (RR, 2.5; CI, 1.2-5.1) were independently associated with the risk of developing tuberculosis.

Conclusions: HIV-infected adults in Cape Town are at high risk of developing tuberculosis irrespective of tuberculin skin testing. The risk increases markedly with HIV disease progression. Patients at extremely high risk can be identified on the basis of demographic and clinical features. Such individuals would be suitable for targeted tuberculosis prophylaxis.