Abstract: Objective To compare the positive detection rates of Mycobacterium tuberculosis (MTB) and the rate of rifampicin resistance in bronchoalveolar lavage fluid (BALF) of patients with pulmonary tuberculosis by different diagnostic methods, and to evaluate the application value of different detection techniques in the clinical diagnosis of pulmonary tuberculosis (PTB). 
Methods A retrospective analysis was performed on 297 patients with PTB treated in Hebei Chest Hospital. BACTEC MGIT960 rapid culture system (culture method), modified acid-fast staining method (staining method), Gene Xpert MTB/RIF system (Xpert method) and TB-DNA PCR-fluorescent probe method (PCR method) were used to detect MTB and rifampicin resistance in BALF samples from the same patient, and to analyze the differences in the results of different diagnostic methods. 
Results The positive detection rates of MTB by culture method, staining method, Xpert method and PCR method were 46.465% (138/297), 30.640% (91/297), 55.556% (165/297) and 36.0364% (108/297), respectively, and the difference was statistically significant (χ2=44.336, P＜0.001). The positive detection rate of MTB by Xpert method was significantly higher than that by the other three methods, and the difference was statistically significant (χ2=4.911, 37.592,  P＜0.05). The positive detection rate of MTB by culture method was significantly higher than that by staining and PCR, and the difference was statistically significant (χ2=15.698, 6.245, P＜0.05). However, staining and PCR showed no difference in positive rates of MTB (P＞0.05). The results of rifampicin resistance detection by culture method, Xpert method and PCR method were 10.145% (14/138), 9.091% (15/165) and 10.185% (11/108), respectively, and the difference was not statistically significant (P＞0.05). 
Conclusion The four detection methods showed great differences in the detection rate of MTB positive in the BALF samples of pulmonary tuberculosis patients. The BACTEC MGIT960 rapid culture system and the Gene Xpert MTB/RIF system can be better applied to the detection of MTB and rifampicin resistance in the BALF of pulmonary tuberculosis patients. In addition, the positive detection rate of MTB by Xpert method is higher and faster, whereas there is no significant difference in the detection rate of rifampicin resistance.

Key words: tuberculosis, pulmonary, bronchoalveolar lavage fluid, staining and labeling