Evaluating the performance of the InnowaveDx MTB/RIF/INH for simultaneous detection of Mycobacterium tuberculosis and resistance to rifampicin and isoniazid

OBJECTIVE: To evaluate the diagnostic performance of the InnowaveDx MTB/RIF/INH assay for the simultaneous detection of Mycobacterium tuberculosis and resistance to rifampicin and isoniazid. METHODS: We evaluated the performance of the InnowaveDx MTB/RIF/INH (InnowaveDx) assay in diagnosing pulmonary tuberculosis and detecting rifampicin and isoniazid resistance at the Zhejiang Hospital of Integrated Traditional Chinese and Western Medicine. RESULTS: Using the clinical final diagnosis as the standard, the sensitivity of InnowaveDx was 68.0%, which was higher than that of acid-fast bacilli smear, MGIT culture, and Xpert (P < .001). The specificity was 97.1%, which was higher than acid-fast bacilli smear (P < .001). The agreement between InnowaveDx and MGIT phenotypic drug sensitivity, as well as Xpert, for detecting rifampicin resistance, had kappa values of 0.783 and 0.940, respectively. The agreement between InnowaveDx and MGIT phenotypic drug sensitivity, as well as multicolor melting curve analysis, for detecting isoniazid resistance, had kappa values of 0.915 and 1. The discrepancies in rifampicin- and isoniazid-resistance detection were observed in 11 and 4 cases, respectively. CONCLUSIONS: The InnowaveDx MTB/RIF/INH assay demonstrates good performance in detecting M. tuberculosis as well as rifampicin and isoniazid resistance. The discrepancies in rifampicin-resistance results and phenotypic resistance are mainly the result of borderline resistance mutations.