SETTING: A central hospital laboratory in South Korea. OBJECTIVE: To evaluate the usefulness of the Xpert® MTB/RIF assay in a country with an intermediate tuberculosis burden. DESIGN: A total of 71 real-time polymerase chain reaction-positive sputum sediments were tested within 24 h by the Xpert MTB/RIF assay. Mycobacterium tuberculosis detection was compared with smear microscopy and culture. Rifampicin (RMP) resistance was compared with a culture-based method and rpoB gene sequencing. We also assessed the limit of detection for mutant proportions and time savings in diagnosis. RESULTS: The Xpert MTB/RIF assay detected M. tuberculosis in 71 (100%) specimens (32 smear-positive, 39 smear-negative). This assay showed 100% (62/62) concordance with drug resistance confirmed by culture and 98.4% (61/62) concordance with sequencing. A specimen containing approximately 50% of mutant p.His526Tyr was falsely interpreted as wild-type bacilli by this assay. The minimal detection ratio was 5:1 of mutant vs. wild-type cells. The median time saved was 18.5 days (range 9-30) for the diagnosis of M. tuberculosis and 81.5 days (65-136) for RMP susceptibility in smear-negative, culture-positive patients. CONCLUSIONS: The Xpert MTB/RIF assay showed high sensitivity in detecting M. tuberculosis with information on RMP resistance, and had a more rapid time to diagnosis compared to conventional tests; however, the location and amount of mutation may affect test sensitivity.
SETTING: A central hospital laboratory in South Korea. OBJECTIVE: To evaluate the usefulness of the Xpert® MTB/RIF assay in a country with an intermediate tuberculosis burden. DESIGN: A total of 71 real-time polymerase chain reaction-positive sputum sediments were tested within 24 h by the Xpert MTB/RIF assay. Mycobacterium tuberculosis detection was compared with smear microscopy and culture. Rifampicin (RMP) resistance was compared with a culture-based method and rpoB gene sequencing. We also assessed the limit of detection for mutant proportions and time savings in diagnosis. RESULTS: The Xpert MTB/RIF assay detected M. tuberculosis in 71 (100%) specimens (32 smear-positive, 39 smear-negative). This assay showed 100% (62/62) concordance with drug resistance confirmed by culture and 98.4% (61/62) concordance with sequencing. A specimen containing approximately 50% of mutant p.His526Tyr was falsely interpreted as wild-type bacilli by this assay. The minimal detection ratio was 5:1 of mutant vs. wild-type cells. The median time saved was 18.5 days (range 9-30) for the diagnosis of M. tuberculosis and 81.5 days (65-136) for RMP susceptibility in smear-negative, culture-positive patients. CONCLUSIONS: The Xpert MTB/RIF assay showed high sensitivity in detecting M. tuberculosis with information on RMP resistance, and had a more rapid time to diagnosis compared to conventional tests; however, the location and amount of mutation may affect test sensitivity.
Authors: Karen R Steingart; Ian Schiller; David J Horne; Madhukar Pai; Catharina C Boehme; Nandini Dendukuri Journal: Cochrane Database Syst Rev Date: 2014-01-21
Authors: Hanna Nebenzahl-Guimaraes; Karen R Jacobson; Maha R Farhat; Megan B Murray Journal: J Antimicrob Chemother Date: 2013-09-20 Impact factor: 5.790
Authors: David J Horne; Mikashmi Kohli; Jerry S Zifodya; Ian Schiller; Nandini Dendukuri; Deanna Tollefson; Samuel G Schumacher; Eleanor A Ochodo; Madhukar Pai; Karen R Steingart Journal: Cochrane Database Syst Rev Date: 2019-06-07