[Molecular diagnosis of tuberculosis]

Metagenomic next-generation sequencing of bronchoalveolar lavage fluid samples offers diagnostic utility in bacteriologically negative pulmonary tuberculosis

Rapid diagnosing Mycobacterium tuberculosis (M. tb) in patients with pulmonary tuberculosis (PTB) cases is critical, particularly in cases without bacteriologically confirmed disease, as it enables timely treatment initiation and can thus interrupt further disease transmission. In this study, the utility of metagenomic next-generation sequencing (mNGS) as a diagnostic tool was evaluated using samples of bronchoalveolar lavage fluid (BALF) samples from 300 bacteriologically negative PTB (BN-PTB) patients hospitalized from January 2020 through December 2023. The diagnostic performance of mNGS was compared to that of acid-fast staining (AFS), conventional Roche culture, and the Xpert method among these BN-PTB patients, using clinical diagnosis as the gold standard. The final analyses enrolled 112 PTB patients and 188 non-PTB cases. These analyses revealed that mNGS-based M. tb detection yields a sensitivity of 94.64 % (106/112), a specificity of 98.94 % (186/188), a positive predictive value (PPV) of 98.15 % (106/108), and a negative predictive value (NPV) of 96.88 % (186/192). This mNGS approach outperformed the AFS, Roche culture, and Xpert methods in terms of sensitivity, specificity, PPV, and NPV (p < 0.05). The superior diagnostic performance of this approach was further supported by its area under the curve and corresponding confidence intervals. Together, these data demonstrate that mNGS can improve the detection of M. tb in BALF samples from BN-PTB patients with high levels of speed, sensitivity, and specificity. This mNGS approach may thus be a valuable diagnostic tool for the rapid detection of M. tb in BN-PTB, providing a foundation for the precision diagnosis and treatment of PTB in the future.

Comparison of the Accuracy of Two Different Molecular Tests for the Diagnosis of Tuberculous Lymphadenitis Using Core Needle Biopsy Specimens: A Diagnostic Accuracy Study

Purpose

To evaluate the diagnostic accuracy of the CapitalBio Mycobacterium real-time polymerase chain reaction assay (CapitalBio test) testing of core needle biopsy (CNB) specimens for tuberculous lymphadenitis (TBL) and to compare it with Xpert MTB/RIF.

Methods

We retrospectively analyzed the medical data on patients with suspected peripheral TBL. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of the CapitalBio test, Xpert MTB/RIF, and parallel test (positive result for either of these two tests) were calculated to evaluate their diagnostic efficacy compared with the final clinical diagnosis.

Results

The study included 114 patients. For diagnosing TBL using CNB samples, the sensitivity, specificity, PPV, NPV, and AUC were 65.0%, 100.0%, 100.0%, 28.6%, and 0.83, respectively, for the CapitalBio test; 72.0%, 100.0%, 100.0%, 33.3%, and 0.86, respectively, for Xpert MTB/RIF; and 82.0%, 100.0%, 100.0%, 43.8%, and 0.91, respectively, for the parallel test.

Conclusion

The accuracy of the CapitalBio test and Xpert MTB/RIF for diagnosing TBL using CNB specimens was moderate, while the sensitivity and NPV of these two tests were relatively low. The diagnostic accuracy of the CapitalBio test was slightly lower than that of Xpert MTB/RIF, but the difference between the two was not statistically significant. Parallel test might improve the diagnostic accuracy but not substantially over a single test.