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Objective: To analyze how demographic, clinical, and laboratory characteristics influence the risk of tuberculosis in human immunodeficiency virus (HIV)-infected individuals; to examine the incidence of tuberculosis associated with change in skin test responsiveness in HIV-infected, tuberculin-negative, nonanergic individuals.

Design: Multicenter cohort study.

Setting: Twenty-three infectious disease units in public hospitals in Italy.

Subjects: A consecutive sample of 3397 HIV-infected subjects were considered for entry in the study. Of these, 2695 who were followed up for at least 4 weeks were enrolled in the study; 739 subjects (27.4%) were unavailable for follow-up. The median duration of follow-up was 91 weeks.

Main Outcome Measure: Culture-proven tuberculosis.

Results: Eighty-three episodes of tuberculosis were observed. Incidence rates of tuberculosis were 5.42 per 100 person-years among tuberculin-positive subjects, 3.00 per 100 person-years among anergic subjects, and 0.45 per 100 person-years among tuberculin-negative nonanergic subjects. In multivariate analysis, being tuberculin-positive (hazard ratio (HR), 9.94; 95% confidence interval (CI), 3.84 to 25.72) or anergic (HR, 3.35; 95% CI, 1.40 to 8.00), or having a CD4 lymphocyte count less than 0.20x109/L (HR, 4.87; 95% CI, 2.35 to 10.11) or between 0.20 and 0.35x109/L (HR, 2.35; 95% CI, 1.09 to 5.05) were statistically significantly associated with the risk of tuberculosis. Incidence of tuberculosis increased with decreasing levels of CD4 lymphocytes in the three groups of subjects with different skin test responsiveness. Skin tests were repeated 1 year after enrollment in 604 tuberculin-negative nonanergic subjects; three cases of tuberculosis were observed among the 13 subjects who converted to tuberculin reactivity.

Conclusions: Risk of tuberculosis in HIV-infected persons can be more precisely quantified by jointly considering skin test reactivity and CD4 lymphocyte count. Periodic skin tests in tuberculin-negative nonanergic individuals can be useful in identifying individuals at high risk of active tuberculosis.

(JAMA. 1995;274:143-148)

Copyright 1995 by the American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use. American Medical Association, 515 N. State St, Chicago, IL 60610.