Impact of smoking on sputum culture conversion and pulmonary tuberculosis treatment outcomes in Brazil: a retrospective cohort study

Objective: To evaluate the impact of smoking on pulmonary tuberculosis (PTB) treatment outcomes and the two-month conversion rates for Mycobacterium tuberculosis sputum cultures among patients with culture-confirmed PTB in an area with a moderate incidence of tuberculosis in Brazil. Methods: This was a retrospective cohort study of PTB patients diagnosed and treated at the Thoracic Diseases Institute of the Federal University of Rio de Janeiro between 2004 and 2012. Results: Of the 298 patients diagnosed with PTB during the study period, 174 were included in the outcome analysis: 97 (55.7%) were never-smokers, 31 (17.8%) were former smokers, and 46 (26.5%) were current smokers. Smoking was associated with a delay in sputum culture conversion at the end of the second month of TB treatment (relative risk = 3.58 [95% CI: 1.3-9.86]; p = 0.01), as well as with poor treatment outcomes (relative risk = 6.29 [95% CI: 1.57-25.21]; p = 0.009). The association between smoking and a positive culture in the second month of treatment was statistically significant among the current smokers (p = 0.027). Conclusions: In our sample, the probability of a delay in sputum culture conversion was higher in current smokers than in never-smokers, as was the probability of a poor treatment outcome.