Tuberculosis infection among cocaine crack users in Brazil

Background WHO recommends treatment for latent tuberculosis infection (LTBI) in the homeless and people who use drugs (PWUD). The optimal test for LTBI screening is uncertain. Methods A cross-sectional study was conducted among the homeless and drug-rehabilitation clinic clients chronically using crack in Western Brazil. Participants were interviewed and offered HIV testing plus tuberculin skin testing (TST) and QuantiFeron®-Gold-in-Tube (QFT). We considered LTBI when either TST or QFT were positive. Factors associated with LTBI were adjusted in a multivariate model. Results Among 372 subjects with at least one valid test, 216 (58%) had LTBI. TST was not read in 18.4%; QFT was indeterminate in 2.5%. TST detected 27 (26%) extra LTBI cases among 75 QFT-negative individuals. PWUD had over three-fold odds for LTBI. TST was 4.5 times more likely to be positive in BCG-vaccinated individuals. Conclusion Given the high risk of progression to disease in this population, the high rates of loss to TST reading and the possibility of false-positive TST results from BCG vaccination, we endorse current CDC recommendations to use QFT for LTBI screening among the homeless and PWUD. However, because adding TST to a negative QFT increased LTBI detection considerably, TST should be considered in QFT-negative individuals.