title: Evaluation of Xpert(®) MTB/RIF assay: diagnosis and treatment outcomes in rifampicin-resistant tuberculosis.
abstract: METHODS
  The Xpert(®) MTB/RIF assay is endorsed by the World Health Organization for the detection of rifampicin (RMP) resistant tuberculosis (TB).
  
  
  OBJECTIVE
  To evaluate Xpert for its diagnostic accuracy in detecting RMP-resistant TB and its impact on treatment outcomes.
  
  
  METHODS
  Patients with available phenotypic drug susceptibility testing (DST) results and those in whom RMP-resistant pulmonary TB was diagnosed using Xpert were evaluated. The accuracy and turnaround time (TAT) of Xpert for determining RMP-resistant TB was calculated. The TATs for treatment between patients diagnosed with RMP-resistant TB using Xpert and those diagnosed without the assay (phenotypic DST group) were compared.
  
  
  RESULTS
  In 321 patients, when phenotypic DST was used as the gold standard, Xpert sensitivity and specificity for RMP resistance diagnosis was respectively 100% and 98.7%; the positive and negative predictive values were respectively 86.2% and 100%. The Xpert group had a much shorter interval from initial evaluation to commencing second-line anti-tuberculosis treatment (64 vs. 2 days, P < 0.001), and negative conversion of mycobacterial cultures (197 vs. 62.5 days, P < 0.001) than the phenotypic DST group.
  
  
  CONCLUSIONS
  Xpert was accurate at diagnosing RMP resistance in this setting with an intermediate TB burden and a low level of RMP resistance. Xpert might reduce disease transmission by reducing the sputum culture conversion times for patients with RMP-resistant TB.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Y W
authors.initials: YW
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: M-W
authors.initials: MW
authors.lastname: Seong
authors.affiliation: Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: T S
authors.initials: TS
authors.lastname: Kim
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: C-G
authors.initials: CG
authors.lastname: Yoo
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Y W
authors.initials: YW
authors.lastname: Kim
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: S K
authors.initials: SK
authors.lastname: Han
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: J-J
authors.initials: JJ
authors.lastname: Yim
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D016896:Treatment Outcome; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000188:drug therapy
chemical_list: D000995:Antitubercular Agents; D012293:Rifampin