Factors associated with sputum culture conversion in multidrug-resistant pulmonary tuberculosis

INTRODUCTION: Sputum culture conversion in pulmonary multidrug-resistant tuberculosis (MDR-TB) is important to make treatment-related decisions and prevent transmission of disease. OBJECTIVE: To identify factors associated with sputum culture conversion, and to determine time to culture conversion and the impact of culture conversion on successful treatment outcomes in MDR-/rifampicin (RMP) resistant TB. METHOD: Retrospective analysis of data from treatment cards and registers of MDR-/RMP-resistant patients initiated on treatment under India's Revised National TB Control Programme in Delhi, West Bengal and Kerala from January 2009 to December 2011. Proportions were calculated and logistic regression analysis was performed. RESULTS: Of 836 patients, 787 were analysed, 651 (83%) of whom experienced culture conversion: respectively 57%, 73% and 79% culture converted by month 3, 4 and 6 of treatment. The median time to culture conversion was 91.3 days. Patients with body mass index (BMI) 16 kg/m2 (OR 0.403, P = 0.001) and 1618 kg/m2 (OR 0.519, P = 0.039) were less likely to have culture conversion. High rates of culture conversion were observed in patients with successful treatment outcomes compared to those without treatment success (462/469, 99% vs. 183/311, 59%; P 0.0001). CONCLUSION: Low BMI is associated with poor sputum culture conversion in MDR-/RMP-resistant TB patients. Lack of culture conversion can impact successful treatment outcomes.