RISK FOR DEVELOPING TUBERCULOSIS AMONG ANERGIC PATIENTS INFECTED WITH HIV

Objective: To assess the risk for development of tuberculosis among anergic pa Design: Retrospective cohort study. Setting: Tertiary referral center. Patients: All HIV-infected patients who had a base-line positive protein purified derivative test (PPD) and delayed-type hypersensitivity skin tests. Measurements: Development of active tuberculosis. Results: Of 374 patients, 108 (29%) had positive results of PPD tests, 154 (41%) had negative results of PPD tests but no skin anergy, and 112 (30%) were anergic. Conversion of the PPD to positive was observed in 10 of 67 (15%) patients with previously negative results of PPD tests and no anergy and in 3 of 36 (8%) anergic patients who were retested during the follow-up period (mean, 26 months). The risk for active tuberculosis to develop in patients not receiving isoniazid chemoprophylaxis was similar in patients with a positive PPD test result (10.4 cases per 100 person-years) and in anergic patients (12.4 cases per 100 person-years) and higher in both groups than in nonanergic patients with a negative PPD test result (5.4 cases per 100 person-years). Tuberculosis was more frequent among intravenous drug abusers with no previous isoniazid treatment (63 of 290, 22%) than among homosexual men (0 of 29) or patients in other HIV transmission categories (0 of 31). Preventive therapy with isoniazid reduced tuberculosis development (4% as compared with 31 %; P = 0.008). Among 15 anergic patients who had CD4 counts measured within 3 months of tuberculosis development, only 1 (7%) had more than 500 CD4 cells/mm3. Conclusions: Anergic HIV-infected patients are at high risk for development of tuberculosis. Anergic HIV-infected patients, in addition to HIV-infected patients with positive results of PPD tests, should be offered preventive therapy if they live in areas with a high prevalence of tuberculosis, at least when the CD4 count decreases to less than 500 CD4 cells/mm3.