Influence of the human immunodeficiency virus in the incidence of tuberculosis in a cohort of intravenous drug users: effectiveness of anti-tuberculosis chemoprophylaxis.

SETTING

A residential program in Barcelona for drug addicts (therapeutic community) admitted between November 1988 and March 1992, and followed until September 1994.

OBJECTIVE

To study the incidence of tuberculosis as related to the presence of tuberculosis infection and/or human immunodeficiency virus (HIV) infection, and to evaluate the protective effect of chemoprophylaxis with isoniazid.

DESIGN

Prospective cohort study. Incidence rates were compared using the Chi-square test for cohort studies. The effectiveness of chemoprophylaxis was evaluated by the Kaplan-Meier method at the univariate level, and by logistic regression models and proportional risks analysis at the multivariate level.

RESULTS

During the study of 361 individuals without previous known tuberculosis or history of anti-tuberculosis chemoprophylaxis, 25 developed tuberculosis, an overall incidence rate of 1.79/100 person-years. For HIV-positive persons, the incidence rate was 3.25/100 person-years, compared with 0.30/100 in those who were HIV-negative (P < 0.05). The highest incidence rates occurred among HIV-positive persons who did not receive chemoprophylaxis and who were either anergic (HIV-positive, purified protein derivative [PPD]-negative, Multitest-negative) or who were infected with Mycobacterium tuberculosis (PPD+), 10.0/100 person-years and 4.64/100 person-years, respectively. Of the 53 persons who received chemoprophylaxis, three developed tuberculosis, an incidence rate of 1.4/100 person-years. In comparison, in the group of 51 patients who were designated to receive chemoprophylaxis but where none was actually taken, 17 developed tuberculosis, an incidence rate of 5.7/100 person-years (P = 0.03).

CONCLUSION

HIV-infected intravenous drug users, particularly those who are anergic or who are PPD positive, are at increased risk of developing tuberculosis. Anti-tuberculosis chemoprophylaxis proved effective in this population.