Evaluation of EZplex MTBC/NTM Real-Time PCR kit: diagnostic accuracy and efficacy in vaccination

Tuberculosis (TB) is mainly caused by Mycobacterium tuberculosis, which is a pathogenic mycobacterial species grouped under Mycobacterium tuberculosis complex (MTBC) with four other pathogenic mycobacterial species. The mycobacteria not included in MTBC are known as nontuberculous mycobacteria (NTM), and cause several pulmonary diseases including pneumonia. Currently, NTM occurrences in TB-suspected respiratory specimens have increased, due to which, precise detection of MTBC and NTM is considered critical for the diagnosis and vaccination of TB. Among the various methods available, real-time PCR is frequently adopted for MTBC/NTM detection due to its rapidness, accuracy, and ease of handling. In this study, we evaluated a new real-time PCR kit for analytical and clinical performance on sputum, bronchial washing, and culture specimens.

For assessing its analytical performance, limit of detection (LOD), reactivity, and repeatability test were performed using DNA samples. To evaluate clinical performance, 612 samples were collected and clinically tested at a tertiary hospital.

LOD was confirmed as 0.584 copies/µL for MTBC and 47.836 copies/µL for NTM by probit analysis (95% positive). For the reactivity test, all intended strains were detected and, in the repeatability test, stable and steady results were confirmed with coefficient of variation ranging from 0.36 to 1.59. For the clinical test, sensitivity and specificity were 98.6%-100% and 98.8%-100% for MTBC and NTM, respectively.

The results proved the usefulness of the kit in TB diagnosis. Furthermore, it could be adopted for the assessment of vaccine efficacy.