Accuracy of the XPert MTB/ RIF® in Broncoalveolar Lavage and Induced Sputum at Tertiary Care Hospital in Rio de Janeiro, Brazil

Pulmonary tuberculosis (PTB) remains an important public health problem worldwide. Rapid molecular tests allowed faster results and greater sensitivity (Se) than sputum smear microscopy and culture for mycobacteria. Studies to assess the performance of Xpert MTB/RIF ® (Xpert) in respiratory samples other than spontaneous sputum are necessary, especially in cases of patients who do not have spontaneous sputum. The aim of this study was to evaluate the performance of Xpert in induced sputum (IS) and bronchoalveolar lavage (BAL) in Rio de Janeiro, the state with the second highest TB incidence rate in Brazil. Diagnostic test study carried out using IS and BAL samples from patients investigating various lung diseases at Thorax Disease Institute of Federal University of Rio de Janeiro, between January 2017 and December 2018. The samples were evaluated through automatized mycobacterial culture and Xpert. Statistical analysis was carried out using culture as the gold standard. 691 samples of IS and BAL were included for analysis. Of 467 BAL samples (68%), 74 were culture positive with 66 Xpert positive and 8 false negatives. In the 393 negative culture samples, 365 were truly negatives, leading to Se, specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) of Xpert of 89%, 93%, 73%, 97%, respectively. Concerning to IS, from the 224 samples (32%), 48 were culture positive with 38 samples Xpert positive and 10 negatives, leading to Se=79%, Sp=91%, PPV=71% and NPV=94%. In our sample, XPert in IS and BAL samples were both useful to diagnose PTB in those patients who are not able to produce spontaneous specimens.