The diagnostic performance of endobronchial ultrasound with Xpert MTB/RIF Ultra in smear-negative pulmonary tuberculosis

ObjectiveThis study investigated the diagnostic performance of endobronchial ultrasound with Xpert MTB/RIF Ultra (Ultra) for detecting smear-negative pulmonary tuberculosis (TB).Methods143 patients suspected of sputum smear-negative pulmonary tuberculosis were enrolled in this study in Shanghai Pulmonary Hospital, China. These patients underwent endobronchial ultrasound with a guide sheath (EBUS-GS) or endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) based on their chest CT manifestations. We assessed the sensitivity and specificity of tissue specimens with Ultra in the TB group and non-TB group. Culture and clinical diagnosis were used as gold-standard for TB.ResultsAmong these 143 patients, 11 patients were culture-positive TB, 85 patients were diagnosed with culture-negative TB and 47 were with the non-TB diseases. Direct testing with microscopy (Acid-Fast Bacilli smear, AFB), liquid culture, pathology, Xpert MTB/RIF(Xpert) test and Ultra had a sensitivity of 8.3%, 11.5%, 42.7%, 64.6%, and 78.1% individually among all the TB patients. Ultra had a higher sensitivity than Xpert (P = 0.011). But Ultra had a specificity of 59.6% (95% CI 44.3-73.3), lower than that of Xpert (89.4%, 95% CI 76.1-96.0, P = 0.001). Ultra had the same sensitivity on specimens from EBUS-TBNA and EBUS-GS (P = 0.975). Ultra's positive predictive value and negative predictive value were 79.8% and 57.1% respectively.ConclusionsTissue specimens from interventional bronchoscopy combined with Ultra provide a sensitive method for diagnosing smear-negative pulmonary tuberculosis, but its specificity was lower than Xpert.