Factors predicting 2-month culture positivity in smear-positive pulmonary tuberculosis

INTRODUCTION: Failure to achieve sputum culture conversion after two months of treatment (M2) for pulmonary tuberculosis (TB) is associated with treatment failure. We aimed to identify the determinants of persistent culture-positive sputum at M2. METHODS: We performed an ancillary study of the multicentric randomized trial FAST-TB, which enrolled adult patients with smear-positive rifampicin-susceptible pulmonary TB in France in 2014-2018. RESULTS: Among the 203 patients enrolled in the FAST-TB study, 177 were evaluated at M2, including 104 with sputum culture: 82 (79 %) culture-negative, and 22 (21 %) culture-positive. Persistence of cough and sputum during follow-up was associated with culture positivity at M2: This was significant for sputum at different time points (respectively 84 % in culture-positive vs. 50 % in culture-negative at M1, 65 % vs. 37 % at M2, and 43 % vs. 17 % at M4, P < 0.05 for all), and for persistent cough at M4 (71 %, vs. 36 %, P = 0.006). Treatment success was similar between groups. CONCLUSION: The main predictors of culture-positive sputum at M2 in patients with smear-positive rifampicin-susceptible pulmonary TB are persistent cough and sputum during treatment. Systematic monitoring of these symptoms could contribute to early detection of patients who may require prolonged anti-TB treatment.