Molecular Techniques for MTBC and NTM Differentiation: Diagnostic Accuracy of STANDARD™ M10 MTB/NTM and Potential Applications

TL;DR

This study evaluates a new molecular test for quickly distinguishing tuberculosis-causing bacteria from non-tuberculous mycobacteria in clinical samples.

Contribution

The study introduces and evaluates the diagnostic accuracy of the STANDARD™ M10 MTB/NTM assay for differentiating MTBC and NTM.

Findings

STANDARD™ M10 showed 85.1% sensitivity and 100% specificity for MTBC detection.

NTM detection sensitivity was 50%, with moderate agreement with culture results.

The test is rapid and automated but does not replace culture for species identification or drug resistance testing.

Abstract

Background. Over the past decade, the World Health Organization has highlighted the need for rapid molecular diagnostics as first-line tools for detecting Mycobacterium tuberculosis complex (MTBC) to strengthen global tuberculosis control. At the same time, infections caused by non-tuberculous mycobacteria (NTM) have become increasingly prevalent, particularly in low TB-burden countries such as Italy. This changing epidemiological scenario underscores the necessity for fast and reliable methods capable of distinguishing NTM from MTBC, a critical step for guiding appropriate treatment. This study evaluated the diagnostic accuracy and potential applications of the STANDARD™ M10 MTB/NTM assay, which simultaneously detects and differentiates MTBC and NTM. Methods. A total of 155 clinical specimens (78.1% respiratory) from patients with suspected mycobacterial infection were tested by fluorescence microscopy, GeneXpert MTB/RIF Ultra (respiratory samples only), STANDARD™ M10 MTB/NTM and culture, used as the reference method. Results. Culture detected MTBC in 54% and NTM (predominantly slow-growing species) in 46% of samples. STANDARD™ M10 showed overall sensitivity and specificity of 70% and 100%, respectively. For MTBC, sensitivity was 85.1% with almost perfect agreement with culture (κ = 0.866), while for NTM, sensitivity was 50% with moderate agreement (κ = 0.566). Sensitivity decreased in microscopy-negative/culture-positive specimens, particularly for NTM. Compared with GeneXpert MTB/RIF Ultra, STANDARD™ M10 exhibited slightly lower sensitivity for MTBC but retained excellent specificity. Conclusions. STANDARD™ M10 MTB/NTM represents a rapid, fully automated tool to support early etiological diagnosis and MTB/NTM differentiation, mainly in selected samples or high-risk patients, but it does not replace culture or molecular tests providing species identification and MTBC drug-resistance profiling.

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