Risk for developing tuberculosis among anergic patients infected with HIV

To assess the risk for development of tuberculosis among anergic patients infected with the human immunodeficiency virus (HIV).

Retrospective cohort study.

Tertiary referral center.

All HIV-infected patients who had a baseline positive protein purified derivative test (PPD) and delayed-type hypersensitivity skin tests.

Development of active tuberculosis.

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.

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.