Effect of cigarette smoking on sputum smear conversion in adults with active pulmonary tuberculosis

Although factors influencing sputum smear conversion in tuberculosis have been studied well, the effect of smoking is largely unknown. Excluding those with incomplete history or drug resistant isolates, 339 patients out of the 526 sputum positive patients registered between1998 and 2000 were studied. At the end of 2 months, smokers and non-smokers converted with almost the same frequency to a negative sputum status {P = 0.065, OR (95%CI) 0.47 (0.21-1.06)}. Although gender or age had no effect on sputum conversion with respect to smoking status, expatriate smokers as a whole showed a significant difference. (P = 0.039). On applying logistic regression model, smokers with far advanced radiographic abnormalities (P < 0.038) or with 3+ smear status (P = 0.011), were found to have a less chance of an early smear conversion. In conclusion smoking did not influence sputum smear conversion in tuberculosis. However, as expatriate smokers and smokers with advanced disease showed a delay in smear conversion, smoking should be discouraged in patients with pulmonary tuberculosis.