An evaluation of Innowave MTB/RIF/INH assay versus Xpert MTB/RIF for rapid identification of <i>Mycobacterium tuberculosis</i> and drug resistance in bone and joint specimens from people with suspected osteoarticular tuberculosis

ABSTRACT Osteoarticular tuberculosis (TB) is hard to diagnose. We prospectively evaluated a novel molecular test, Innowave MTB/RIF/INH (InnowaveDX), against culture and Xpert MTB/RIF (Xpert)/MeltPro TB for detecting Mycobacterium tuberculosis (MTB) and rifampicin and isoniazid resistance in osteoarticular TB. Pus/tissue samples from suspected osteoarticular TB patients were tested by smear, culture, Xpert, and InnowaveDX; drug-susceptibility testing was conducted on MTB isolates. A comprehensive reference standard (CRS), which included clinical, laboratory, histopathological, and radiological data, was used as the gold standard. From June 2024 to January 2025, 150 suspected osteoarticular TB patients were enrolled. Eighty patients met CRS-TB criteria. The sensitivity of InnowaveDX for MTB detection was 95% (76/80), surpassing Xpert (87.5%), culture (35%), and smear (16.25%). Both InnowaveDX and Xpert correctly identified 4 rifampicin-resistant and 22 sensitive cases. For isoniazid, InnowaveDX detected 6/8 resistant and 20/20 sensitive cases, versus 2/3 and 12/14 for MeltPro TB. The concordance of InnowaveDX with phenotypic DST was 94.7% both for the resistance diagnosis of rifampicin and isoniazid. InnowaveDX detects significantly more osteoarticular TB cases than Xpert or culture and simultaneously identifies rifampicin and isoniazid resistance, enabling rapid diagnosis and tailored therapy. IMPORTANCE This study shows that Innowave MTB/RIF/INH is a faster and more sensitive test for diagnosing osteoarticular tuberculosis (TB) than current methods. Compared with culture and Xpert MTB/RIF, Innowave detects more TB cases from bone and joint samples, which usually contain very few bacteria. Importantly, it can simultaneously identify resistance to rifampicin and isoniazid within a few hours, instead of waiting weeks for culture-based results. This allows doctors to start the right anti-TB treatment earlier, reduce unnecessary empirical therapy, and lower the risk of joint destruction and disability. Overall, Innowave offers a practical solution to improve early diagnosis and drug-resistance detection in difficult-to-diagnose extrapulmonary TB.