A High Sensitive Detection of Droplet Digital PCR for the Diagnosis of Pulmonary Tuberculosis

Purpose: Rapid and accurate diagnosis of Mycobacterium tuberculosis (MTB) in the patients with pulmonary tuberculosis (PTB) is essential for the patients management and infection control, particularly in cases with negative results from conventional bacteriological tests, as early detection enables timely initiation of treatment and interruption of disease transmission. Patients and Methods: We evaluated the diagnostic performance of a dual-target droplet digital PCR (ddPCR) assay, targeting IS6110 and IS1081 , using bronchoalveolar lavage fluid (BALF) samples collected from 506 hospitalized patients including 397 PTB and 109 non-PTB from August 2024 to December 2024. The performance of ddPCR was compared with that of MGIT960 culture, real-time quantitative PCR (qPCR), multi-color melting curve analysis (MMCA), and GeneXpert MTB/RIF (Xpert). Results: The ddPCR assay demonstrated a sensitivity of 89.7% (95% CI: 86.3– 92.3%), specificity of 89.0% (95% CI: 81.5– 94.0%), positive predictive value (PPV) of 96.7% (95% CI: 94.5– 98.1%), and negative predictive value (NPV) of 70.3% (95% CI: 61.8– 77.6%). The overall concordance rate was 89.5% (95% CI: 86.5– 91.9%), with a Kappa value of 0.768 (95% CI: 0.712– 0.824). The superior diagnostic performance of ddPCR was further supported by an area under the receiver operating characteristic (ROC) curve (AUC) of 0.893 (95% CI: 0.855– 0.931). In a subgroup analysis of 216 bacteriologically negative PTB cases, ddPCR exhibited a sensitivity of 81.9%, which was significantly higher than that of Xpert (34.3%), MMCA (17.6%), and qPCR (31.0%) (all P < 0.001). Conclusion: The dual-target ddPCR assay targeting IS6110 and IS1081 offers a rapid, sensitive, and accurate method for the diagnosis of pulmonary tuberculosis. Its cost-competitiveness and manageable workflow make it a promising tool for clinical practice.