Molecular drug susceptibility testing in the Netherlands: performance of the MTBDRplus and MTBDRsl assays

BACKGROUND: The performance of molecular drug susceptibility testing in countries with a low prevalence of drug resistance, such as the Netherlands, has not been adequately studied. OBJECTIVE: To evaluate the diagnostic accuracy of the GenoType (R) MTBDRplus and MTBDRsl assays to detect resistance to first- and second-line anti-tuberculosis drugs in the context of a nationwide screening programme in the Netherlands. RESULTS: The MTBDRplus assay had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 99%, 80% and 100% for detecting rifampicin resistance. The sensitivity, specificity, PPV and NPV of either a katG or inhA mutation for detecting isoniazid resistance were 88%, SUMMARY 100%, 100% and 99%. The MTBDRsl assay had a sensitivity, specificity, PPV and NPV of 100%, 99%, 83%, and 100% for detecting moxifloxacin resistance; 62%, 71%, 58% and 74%, respectively, for detecting ethambutol resistance; 86%, 99%, 86% and 99% for detecting amikacin resistance; and 50%, 96%, 71% and 91% for detecting capreomycin resistance. CONCLUSION: The MTBDRp/us and MTBDRs/ assays may aid in decision making in tuberculosis treatment in low-level drug resistance settings and should preferably be used to exclude resistance.