The MTP64 antigen in bronchoalveolar lavage fluid is crucial for diagnosing pulmonary tuberculosis

Background: Recent research on the use of the MPT64 antigen of Mycobacterium tuberculosis (MTB) in tuberculosis diagnosis has intensified. However, its detection in bronchoalveolar lavage fluid (BALF) has not been previously documented. This study aims to fill that gap. Methods: From May 2021 and July 2023, we enrolled 104 pulmonary tuberculosis (PTB) patients:59 with bacteriologically confirmed PTB (BC-PTB) and 45 with clinically diagnosed PTB with negative pathogens (CD-PTB). A control group included 72 non-tuberculous patients (Non-TB). We used enzyme-linked immunosorbent assay (ELISA) to detect the MPT64 in BALF. Its diagnostic value for pulmonary tuberculosis was preliminarily explored and compared with that of acid-fast bacteria (AFB) staining and Xpert MTB/RIF. Results: MPT64 showed a sensitivity of 59.62% (95% CI: 50.01%–68.54%) in 104 cases, significantly higher than AFB (26.92%,P < 0.001) and slightly higher than Xpert MTB/RIF (56.73%,P = 0.673,not statistically significant).Its specificity was 88.89%(95% CI: 79.58%–94.26%),lower than both AFB and Xpert MTB/RIF (100%,P = 0.006).Sensitivities for BC-PTB and CD-PTB were 64.41%(95% CI: 51.66%–75.40%) and 53.33% (95% CI: 39.08%–67.06%), respectively, with no significant difference (P = 0.314). Conclusion : The use of ELISA to detect the MPT64 in BALF may serve as an important supplementary diagnostic method for pulmonary tuberculosis, particularly for bacterial-negative pulmonary tuberculosis.