Incidence of tuberculosis and the importance of treatment of latent tuberculosis infection in a Spanish prison population

OBJECTIVE: To establish the incidence of tuberculosis (TB) in a prison population and its link with latent tuberculosis infection treatment (LTIT). METHODS: From 1991 to 1999 a TB programme was run in a Spanish prison. A cohort study was conducted to know TB incidence and the associated variables. RESULTS: Of 1050 people studied, 10% were co-infected by the human immunodeficiency virus (HIV) and Mycobacterium tuberculosis. Twenty-three cases of TB were detected, an incidence rate of 6.39 per 1000 person-years of follow-up. Multivariate analysis showed HIV-infected patients (RR 4.07, 95%CI 2.61-6.35), and those infected by M. tuberculosis who did not undergo LTIT (RR 10.15, 95%CI 0.90-50.59) to be at greater risk of developing TB. In TST reactors, those co-infected with HIV (RR 10.15, 95%CI 3.80-27.07) and those who had not undergone LTIT (RR 8.53, 95%CI 1.12-64.86) were shown to be at the greatest risk of developing TB. CONCLUSIONS: The observed incidence of TB is much higher in prisons than in the community at large. HIV-M. tuberculosis co-infection appears as the main risk factor for developing TB, while LTIT significantly reduces incidence.