Accuracy of cobas MTB and MTB-RIF/INH for Detection of Mycobacterium tuberculosis and Drug Resistance

Abstract

This study evaluated the performance of cobas MTB and cobas MTB-RIF/INH for the diagnosis of tuberculosis and detection of rifampicin (RIF) and isoniazid (INH) resistance. Adults presenting with pulmonary tuberculosis symptoms were recruited in South Africa, Moldova, and India. Performance of cobas MTB was assessed against culture, whereas cobas MTB-RIF/INH was assessed using phenotypic drug susceptibility testing and whole-genome sequencing as composite reference standards. Xpert MTB/RIF (Xpert) or Xpert MTB/RIF Ultra (Ultra) was used as a comparator. The overall sensitivity and specificity of cobas MTB were 95% (95% CI, 93%–96%) and 96% (95% CI, 95%–97%). Among smear-negatives, the sensitivity of cobas MTB was 75% (95% CI, 66%–83%). Among participants tested with both cobas MTB and Xpert, sensitivity was 96% (95% CI, 94%–97%) for cobas MTB and 95% (95% CI, 93%–97%) for Xpert. Among participants tested with both cobas MTB and Ultra, sensitivity was 88% (95% CI, 81%–92%) for cobas MTB and 89% (95% CI, 83%–93%) for Ultra. Sensitivity and specificity of cobas MTB-RIF/INH for RIF and INH detection were 90% (95% CI, 84%–94%) and 100% (95% CI, 99%–100%), and 89% (95% CI, 84%–93%) and 99.5% (95% CI, 98%–100%), respectively. The cobas MTB and cobas MTB-RIF/INH assays exhibited high performance in a diverse population and present a suitable option for molecular detection of tuberculosis and RIF and INH resistance.