Validation of the GenoType MTBDR Ver 2.0 assay for detection of rifampicin and isoniazid resistance in complex isolates at UZCHS-CTRC TB research laboratory.

Background: Multidrug-resistant tuberculosis (MDR-TB) is a public health concern globally. MDR-TB is defined as resistance to rifampicin (RIF) and isoniazid (INH), the two-major anti-TB first-line TB treatment drugs. Rapid identification of MDR-TB can contribute significantly to the control of TB. The GenoType MTBDRplus Ver 2.0 assay is a molecular assay used to detect genetic mutations that result in RIF and INH resistance. The aim of this study was to validate the performance of the GenoType MTBDRplus Ver 2.0 assay for the detection of INH and RIF resistance.

Methods: Fifty-five stored Mycobacterium tuberculosis isolates were tested using both the mycobacterial growth indicator tube (MGIT), antimicrobial susceptibility testing (AST), and the GenoType® MTBDRplus Ver 2.0 assay. The MGIT AST was done according to the BBL MGIT AST SIRE system with RIF and INH final critical concentrations of 1.0 μg/ml and 0.1 μg/ml, respectively. The GenoType MTBDRplus assay (Hain Lifescience, Germany) was performed following the manufacturer's instructions.

Results: The GenoType MTBDRplus Ver 2.0 assay had a sensitivity, specificity, positive predictive value, and negative predictive value of 100% for INH and RIF resistance. The intra-assay precision for the assay was 100%.

Conclusion: The GenoType MTBDRplus Ver 2.0 assay's sensitivity and specificity show that the assay is highly accurate for the detection of RIF and INH resistance and thus can be used as an alternate platform due to its shorter results turnaround time.