Performance Assessment of the GenoType®MTBDRplus Assay for Rapid Detection of Multidrug-Resistant Tuberculosis among Clinical Isolates in Low Tuberculosis Burden Setting

Introduction: New molecular assays for rapid Multidrug-Resistant Tuberculosis (MDR-TB) detection continue to be developed. Rwanda has recently introduced the line probe assay for early TB and MDR-TB diagnosis. We aimed to assess the performance of GenoType® MTBDRplus test before its implementation in the routine testing. Methods: Sputum samples from suspected MDR-TB patients received and processed at Rwanda National Reference Laboratory from 2010-2012 were included in this study. The performance of Genotype® MTBDRplus assay was evaluated versus the standard phenotypic conventional Drug Susceptibility Testing (DST) on Lowenstein Jensen. Sensitivity, specificity and predictive values (positive and negative) were calculated. Statistical analyses were performed using Epi Info version 3.5.3. P-values were derived from χ2 tests applying Fisher Exact where appropriate. Results: A total of 1548 participants were enrolled in this study, 463 (29.9%) were from new patients and 1085 (70.1%) patients were from retreated patients. The GenoType® MTBDRplus assay correctly identified 37 of 39 Isoniazid resistant strains; 33 of 36 Rifampicin resistant; and 30 of 32 MDR-TB strains for both tests. Compared to the reference standard, the sensitivity of the GenoType® MTBDRplus assay was 94.8% (95% CI: 79.2-99.2%) to detect Isoniazid resistance, 91.7% (95% CI: 77.5-98.2%) for Rifampicin and 93.8% (95% CI: 79.2-99.2%) for the combination of both, MDR-TB. The specificity was 99.3% for Isoniazid, 98.6% for Rifampicin and 99% for MDR-TB. Positive Predictive Value of GenoType® MTBDRplus assay was 96.8% for MDR-TB and its Negative Predictive value 98.6%. The GenoType® MTBDRplus performed well in identifying MDR-TB. Conclusion: GenoType® MTBDRplus assay is a rapid and reliable test in detecting MDR-TB cases in Rwanda. Therefore, GenoType®MTBDRplus assay can be recommended for detecting MDR-TB in our setting to speed out MDR-TB detection in order to institute early treatment.