Evaluation of Xpert^®<i>Mycobacterium tuberculosis</i>/rifampin in sputum-smear negative and sputum-scarce patients with pulmonary tuberculosis using bronchoalveolar lavage fluid

Context Sputum smear-negative and sputum-scarce pulmonary tuberculosis (PTB) is a diagnostic challenge. Xpert ® Mycobacterium tuberculosis/rifampin (MTB/RIF) provides a rapid diagnosis on high-quality biological specimen obtained by bronchoscopy. Aims The aim of this study is to evaluate Xpert ® MTB/RIF on bronchoalveolar lavage (BAL) fluid in sputum smear-negative and sputum-scarce PTB patients. Settings Tertiary care hospital in India. Design This was prospective observational study. Materials and methods Between January 2015 and November 2016, we prospectively recruited sputum-smear negative and sputum-scarce patients under evaluation for PTB and performed BAL. Sensitivity, specificity, positive, and negative predictive values were calculated for the diagnosis of PTB on BAL fluid for acid-fast bacilli smear and Xpert ® MTB/RIF using liquid culture as the reference standard and compared to the final diagnosis based on composite reference standard. Sensitivity, specificity, and predictive values were calculated with 95% class intervals. McNemar's test was used for comparison of sensitivities. Results Of the 60 patients included, 52 (88.3%) had a final diagnosis of PTB and 16 (26.7%) were culture confirmed. Xpert ® MTB/RIF had a sensitivity and specificity of 81% (54%-96%) and 73% (56%-85%) in culture confirmed cases; 46% (32%-60%) and 100% (63%-100%) for the final diagnosis; 32% (17%-51%) and 100% (54%-100%) in culture negative cases, respectively. Culture had a sensitivity of 32% (20%-47%) for the final diagnosis. Conclusions In sputum smear-negative and sputum-scarce patients with clinico-radiological features of PTB Xpert ® MTB/RIF has good sensitivity for diagnosis on BAL fluid. It is useful even when cultures are negative.