Using Bronchoalveolar Lavage Fluid for Active Pulmonary Tuberculosis Laboratory Diagnosis

Abstract Objective: To evaluate the diagnostic efficiency of bronchoalveolar lavage fluid (BALF) for MycobacteriumTuberculosis (MTB) infection using laboratory methods. Methods: A retrospective study was conducted in patients diagnosed with active pulmonary tuberculosis (APTB) and lacking sputum quality/quantity. BALF collected during the operation processes of Electric bronchoscopy were tested using Ziehl-Neelsen staining acid-fast bacilli smear microscopy (Z-N-AFB-SM), GeneXpert MTB/RIF（Xpert），loop-mediated isothermal amplification (LAMP), or culturing with BACTEC™ Mycobacterial Growth Indicator Tube™ 960 (MGIT). Chi-square test was used for statistic analysis. Results: 331 suspected APTB patients were enrolled in this study. 224 of them were sputum-scarce. 89 were sputum-sufficient andnegative in both Z-N-AFB-SM and MGIT 960 testing. Of the sputum sufficient patients, BALF-testing confirmed APTB diagnosis in 20.2% (18/89) via Z-N-AFB-SM, and 53.0% (35/89) via MGIT. The total positive rates of BALF testing via four aforementioned methods were 18.2% (57/313), 66.4% (168/253), 61.0% (83/136) and 48.2% (140/290) respectively. The positive rate of MTB discovered in BALF collected by well-trained respiratory physicians are significantly higher than those collected by anesthetists (χ2=22.48, P<0.01). Total adverse events incidence of BAL was 1.9% (6/313). Conclusion: BALF has a similar sensitivity and specificity for APTB laboratory diagnosis. It can be used as a complementary diagnostic method for APTB when sputum availability is poor. The proficiency of BALF collection is an important factor affecting the detection results.