Time to culture conversion in smokers with pulmonary tuberculosis

It has been reported that tobacco smoking slows the sterilisation of sputum culture in pulmonary tuberculosis, but the factors that could delay culture conversion in patients who smoke are not known. Our aim is to identify the factors influencing sputum culture conversion in smokers with pulmonary tuberculosis.

Ninety-nine patients with a smoking history and diagnosed with pulmonary tuberculosis were analysed retrospectively. The relationship between sputum culture status at the second month and the following variables: age, gender, pack-years index, comorbid diseases, number acid-fast bacilli (AFB) in sputum smear examination, radiological findings (cavitary, extensive or limited disease), drug susceptibility pattern and initial treatment, was analysed. The Student t-test, chi-square test and logistic regression model with forward stepwise conditional methods were used for statistical analysis. A p value of <0.05 was considered to be statistically significant.

Twenty six patients (26.2%): 18 males (22.2%) and 8 females (44%) were sputum culture positive at the end of the second month of treatment. In univariate analysis, culture conversion time was significantly associated with female gender and extensive disease, but in a logistic regression analysis was only correlated with female gender (OR=5.63 95% CI 1.21-20.64-p=0.02).

In current smokers with pulmonary tuberculosis, the 'time to culture' conversion relates only to the female gender.