A Prospective Study of the Risk of Tuberculosis among Intravenous Drug Users with Human Immunodeficiency Virus Infection

To determine the risk of active tuberculosis associated with human immunodeficiency virus (HIV) infection, we prospectively studied 520 intravenous drug users enrolled in a methadone-maintenance program. Tuberculin skin testing and testing for HIV antibody were performed in all subjects. Forty-nine of 217 HIV-seropositive subjects (23 percent) and 62 of 303 HIV-seronegative subjects (20 percent) had a positive response to skin testing with purified protein derivative (PPD) tuberculin before entry into the study. The rates of conversion from a negative to a positive PPD test were similar for seropositive subjects (15 of 131; 11 percent) and seronegative subjects (26 of 202; 13 percent) who were retested during the follow-up period (mean, 22 months). Active tuberculosis developed in eight of the HIV-seropositive subjects (4 percent) and none of the seronegative subjects during the study period (P<0.002). Seven of the eight cases of tuberculosis occurred in HIV-seropositive subjects with a prior positive PPD test (7.9 cases per 100 person-years, as compared with 0.3 case per 100 person-years among seropositive subjects without a prior positive PPD test; rate ratio, 24.0; P<0.0001). We conclude that, although the prevalence and incidence of tuberculous infection were similar for both HIV-seropositive and HIV-seronegative intravenous drug users, the risk of active tuberculosis was elevated only for seropositive subjects. These data also suggest that in HIV-infected persons tuberculosis most often results from the reactivation of latent tuberculous infection; our results lend support to recommendations for the aggressive use of chemoprophylaxis against tuberculosis in patients with HIV infection and a positive PPD test. EPIDEMIOLOGIC surveillance data in the United States have suggested an important association between tuberculosis and the acquired immunodeficiency syndrome (AIDS). Increasing rates of tuberculosis have been noted in areas with high concentrations of AIDS cases, and comparisons of tuberculosis registries and AIDS registries in several regions have indicated considerable overlap.^{1 2 3 4 5} Hospital-based studies have suggested that 10 percent or more of patients with AIDS may also have tuberculosis; the risk of tuberculosis is particularly high among nonwhites and among intravenous drug users.^{1,2,6 7 8 9 10} Seroprevalence studies of patients with tuberculosis in regions with high numbers of AIDS cases have found an increased prevalence…