Diagnostic usefulness of the GenoType MTBDRplus assay for detecting drug-resistant tuberculosis using AFB smear-negative specimens with positive TB-PCR result

AbstractBackground The aim of this study was to evaluate the diagnostic accuracy of the GenoType MTBDRplus assay in detecting drug-resistant tuberculosis (DR-TB) by using acid-fast bacilli (AFB) smear-negative specimens with positive TB-PCR results. Methods The MTBDRplus assay was performed with 2 different categories of 117 samples, including AFB smear-positive specimens (n = 53) and AFB smear-negative specimens (n = 64), which exhibited positive TB-PCR results, at a single institution. The results were retrospectively compared with the results of the phenotypic drug susceptibility test (DST), for reference. Results A total of 105 tests were finally analyzed. Of these, 54 tests were conducted using AFB smear-negative specimens with positive TB-PCR results. The MTBDRplus assay for these 54 samples demonstrated a sensitivity of 100%, specificity of 98%, positive predictive value (PPV) of 75%, and negative predictive value (NPV) of 100% in detecting rifampicin resistance. With these same species, the sensit...