Evaluation of the GCdiaMTB/NTM real-time PCR kit according to the Korean in vitro diagnostic medical device approval standards.

BACKGROUND: Mycobacterium tuberculosis complex (MTBC) and non-tuberculous mycobacterial (NTM) infections present with similar clinical symptoms but require different treatments, so accurate, rapid differential diagnosis is essential. While traditional methods, such as acid-fast bacilli (AFB) microscopy and culture, are time-consuming, molecular diagnostics offer a faster alternative. METHODS AND RESULTS: This study evaluated the clinical performance of the GCdiaMTB/NTM Real-Time PCR Kit (GCdia) for diagnosing MTBC and NTM infections. The kit was compared to a licensed product, the AdvansureTB/NTM real-time PCR kit (Advansure), using 660 residual sputum and culture specimens from patients suspected of having pulmonary tuberculosis (TB) and NTM infections, classified using a composite reference standard (AFB culture, with the MPT64 antigen test used to differentiate MTBC from NTM in positive cultures). The kit's performance was evaluated in accordance with the Korean Ministry of Food and Drug Safety (MFDS) in vitro diagnostic medical device (IVD) approval standards. For sputum specimens, GCdia showed 100% sensitivity and 99.32% specificity for MTBC, and 100% sensitivity and 100% specificity for NTM (95% CI reported for all estimates in Table 3). In a paired comparison using the exact McNemar test, GCdia showed a statistically significant advantage over Advansure for NTM sensitivity in sputum (10.77 percentage points; 95% CI 3.23-18.31; p = 0.016); differences in MTBC sensitivity in sputum and in both targets in culture specimens were not statistically significant. Agreement between GCdia and Advansure was excellent across all specimen and target categories (Cohen's kappa 0.921-1.000). CONCLUSIONS: GCdia showed clinical performance comparable to, or in one comparison significantly higher than, Advansure, and met all predefined Korean MFDS regulatory thresholds. Because the reference standard used for NTM classification does not include species-level confirmation, interpret these findings as applying to broad detection of NTM growth rather than species-specific diagnostic accuracy. Our findings provide a practical guide for researchers and companies preparing for Korean IVD approval.