Role of bronchial aspirate samples for the diagnosis of pulmonary tuberculosis in patients with negative smear and negative Xpert MTB/Rif in sputum

Abstract

Background: In 2018 one-third of pulmonary TB (PTB) cases in the Republic of Moldova missed the microbiological confirmation, that despite the universal access to Xpert MTB/Rif (Xpert) assay and to TB culture. Use of bronchial specimens have been suggested as a useful tool for microbiological confirmation of smear negative PTB. Aim: To assess the added value and diagnostic accuracy of the standard TB microbiological tests (microscopy, Xpert, culture) in bronchial aspirate (BA) for the diagnosis of pulmonary tuberculosis in patients with negative smear and Xpert results in sputum. Methods: We retrospectively reviewed microbiological and basic clinical characteristics of all patients who were consulted for suspected PTB at the Institute of Phthtisiopneumology in Moldova during 2017-2018 and had both negative smear and Xpert results in sputum samples and in whom BA by flexible bronchoscopy was obtained. Results: 705 cases with complete dataset have been analysed. Of them 39 (5.5%) cases had positive TB culture (23 - only in bronchial aspirate, 9 - in both aspirate and sputum and 7 - only in sputum). Smear microscopy was positive in 1,8% (13 cases) and Xpert in 4,2% (30 cases) of BA samples. The sensitivity and specificity of Xpert in BA were 46.1% (95%CI, 31.6% – 61.4%) and 98.2% (95%CI, 96.9% - 99.0%), respectively, and those for microscopy were 20.5% (95%CI, 10.8% - 3.5%) and 99.2% (95%CI, 98.5% - 99.7%), respectively, when compared to the culture. Conclusion: Assessment of BA by standard microbiological tools could improve the rate of microbiological confirmation and potentially reduce the time to treatment initiation in patients with PTB.