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

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.

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.

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.

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.