The utility of Xpert MTB/RIF performed on bronchial washings obtained in patients with suspected pulmonary tuberculosis in a high prevalence setting

摘要

Background Xpert MTB/RIF has been shown to have a superior sensitivity to microscopy for acid fast bacilli (AFB) in sputum and has been recommended as a standard first line investigation for pulmonary tuberculosis (PTB). Bronchoscopy is a valuable tool in diagnosing PTB in sputum negative patients. There is limited data on the utility of Xpert MTB/RIF performed on bronchial lavage specimens. Our aim was to evaluate the diagnostic efficiency of Xpert MTB/RIF performed on bronchial washings in sputum scarceegative patients with suspected PTB. Methods All patients with a clinical and radiological suspicion of PTB who underwent bronchoscopy between January 2013 and April 2014 were included. The diagnostic efficiencies of Xpert MTB/RIF and microscopy for AFB were compared to culture for Mycobacterium tuberculosis. Results Thirty nine of 112 patients were diagnosed with culture-positive PTB. Xpert MTB/RIF was positive in 36/39 with a sensitivity of 92.3?% (95 % CI 78–98?%) for PTB, which was superior to that of smear microscopy (41?%; 95 % CI 26.0–57.8?%, p?=?0.005). The specificities of Xpert MTB/RIF and smear microscopy were 87.7?% (95 % CI 77.4–93.9?%) and 98.6?% (95 % CI 91.6?%–99.9?%) respectively. Xpert MTB/RIF had a positive predictive value of 80?% (95 % CI; 65–89.9?%) and negative predictive value of 95.5?% (95 % CI 86.6–98.8?%). 3/9 patients with Xpert MTB/RIF positive culture negative results were treated for PTB based on clinical and radiological findings. Conclusion Xpert MTB/RIF has a higher sensitivity than smear microscopy and similar specificity for the immediate confirmation of PTB in specimens obtained by bronchial washing, and should be utilised in patients with a high suspicion of pulmonary tuberculosis.