Evaluating a Dual-Gene qPCR Melting Curve Assay for Rapid Detection of Tuberculosis in Suspected Pulmonary Cases

Purpose New economic, rapid, and efficient diagnostic methods are desirable for the control of tuberculosis. This study aimed to evaluate the performance of a dual-gene qPCR melting curve assay (DGPMC) in detecting tuberculosis among patients with suspected pulmonary tuberculosis. Patients and methods The DGPMC assay based on rpoB and IS6110 gene sequences has been established for detection of Mycobacterium tuberculosis . A prospective study was conducted among adult patients with suspected pulmonary tuberculosis from June 2021 to September 2023 at Shanghai Pulmonary Hospital, China. All patients received symptom assessment, high-resolution chest CT scan, and bronchoscopy. Bronchoalveolar lavage fluid was collected for mycobacterial culture and acid-fast staining, GeneXpert MTB/RIF, and DGPMC assay. The diagnostic performance of DGPMC assay was evaluated against the composite reference standard. Results Overall, 240 patients were included in this trial, including 80 (33.3%) asymptomatic patients. Clinical diagnosis of tuberculosis was confirmed in 191 (79.6%) patients and 49 (20.4%) patients were confirmed without tuberculosis. The overall sensitivity of the DGPMC assay was 55.0% (95% CI: 47.6-62.1%), and the corresponding specificity was 85.7% (95% CI: 72.1-93.6%) in the diagnosis of tuberculosis. The sensitivity of DGPMC assay was higher than that of GeneXpert test (55.0% vs 47.1%, P = 0.038). The Youden index and weighted Youden index of the DGPMC assay were 40.7% and 28.4%, respectively. Subgroup analyses demonstrated that the sensitivity was 32.4% (95% CI: 22.3-44.4%) in the individuals with negative results for both culture and GeneXpert test. The DGPMC assay performed significantly better than the melting curves based on rpoB gene or IS6110 gene alone (P = 0.0000; P = 0.0020). Conclusion The DGPMC assay is an alternative tool favorable for the detection of tuberculosis in patients with suspected pulmonary tuberculosis, especially in the patients with low bacterial load.