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Utility of Rapid Molecular Assays for Detecting Multidrug-Resistant Mycobacterium tuberculosis in Extrapulmonary
Katarzyna Kania1,2, Katarzyna Wójcik3, Kamil Drożdż4
1Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Jagiellonian University Medical College, ul. Medyczna 9, 30-688 Krakow, Poland.
Diagnostics (Basel, Switzerland)
|May 14, 2025
Summary
Rapid molecular assays are effective for diagnosing extrapulmonary tuberculosis (TB) and detecting multidrug-resistant TB (MDR-TB). These WHO-recommended tests offer high accuracy and speed, aiding in critical early detection for targeted treatment.
Area of Science:
- Clinical microbiology
- Infectious diseases
- Molecular diagnostics
Background:
- Extrapulmonary tuberculosis (TB) diagnosis is challenging, especially with multidrug-resistant (MDR) strains.
- Rapid molecular assays, validated for pulmonary TB, require assessment for extrapulmonary TB utility.
- Early detection of drug resistance in TB is crucial for effective treatment.
Purpose of the Study:
- To evaluate the performance of WHO-recommended rapid molecular assays for diagnosing extrapulmonary TB.
- To assess the ability of these assays to detect multidrug-resistant Mycobacterium tuberculosis complex (MTBC).
- To compare molecular assay results with phenotypic drug susceptibility testing (DST).
Main Methods:
- Analysis of 6274 clinical samples (4891 pulmonary, 1383 extrapulmonary) from 2019-2022.
- Utilized BD MAX™ MDR-TB, Xpert® MTB/RIF, Xpert® MTB/XDR, and FluoroType MTB assays.
- Compared molecular results with phenotypic DST using Löwenstein-Jensen and BACTEC™ MGIT™ liquid cultures.
Main Results:
- MTBC detected in 426 samples by BD MAX; 50 from extrapulmonary sites.
- BD MAX demonstrated high sensitivity (93.1%) and specificity (98.4%) for extrapulmonary TB.
- 11% of MTBC-positive cases showed resistance to isoniazid/rifampicin; 3.69% were MDR-TB.
- Molecular assays accurately detected resistance mutations with high concordance to DST (κ = 0.69-0.89).
Conclusions:
- Molecular assays validated for pulmonary TB are reliable for extrapulmonary TB diagnosis and drug resistance profiling.
- Rapid turnaround and accuracy support broader implementation in routine diagnostics.
- These assays are particularly valuable for challenging extrapulmonary specimens, enabling timely, targeted therapy.
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