title: Xpert MTB/Rif for the diagnosis of extrapulmonary tuberculosis--an experience from a tertiary care centre in South India.
abstract: OBJECTIVE
  The Xpert MTB/Rif, with a detection limit of 131 CFU/ml, plays a valuable role in the diagnosis of extrapulmonary tuberculosis, both susceptible and resistant. This study aims at evaluating the Xpert MTB/Rif for the same, at a tertiary care centre in south India, assessing it against both culture and a composite gold standard (CGS).
  
  
  METHODS
  We tested consecutive samples from patients suspected of extrapulmonary tuberculosis with Xpert MTB/Rif, evaluated its sensitivity and specificity against solid and/or liquid culture and CGS. An individual analysis of different sample types (tissue biopsies, fluids, pus, lymph node biopsies and CSF) given an adequate sample size, against both culture and CGS, was also performed.
  
  
  RESULTS
  In total, 494 samples were analysed against culture. Compared to culture, the sensitivity of Xpert MTB/Rif was 89% (95% CI 0.81-0.94) and its specificity was 74% (95% CI 0.70-0.78). When Xpert MTB/Rif was compared to the CGS, pooled sensitivity was 62% (95% CI 0.56-0.67) and specificity was 100% (95% CI 0.91-1.00).
  
  
  CONCLUSIONS
  This assay performs better than the currently available conventional laboratory methods. The rapidity with which results are obtained is an added advantage, and its integration into a routine diagnostic protocol must be considered.
authors.affiliation: Department of Microbiology, Christian Medical College, Vellore, India.
authors.forename: Shirly
authors.initials: S
authors.lastname: Suzana
authors.affiliation: Department of Microbiology, Christian Medical College, Vellore, India.
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Ninan
authors.affiliation: Department of Biostatistics, Christian Medical College, Vellore, India.
authors.forename: Mahasampath
authors.initials: M
authors.lastname: Gowri
authors.affiliation: Department of Spinal Disorders, Christian Medical College, Vellore, India.
authors.forename: Krishnan
authors.initials: K
authors.lastname: Venkatesh
authors.affiliation: Department of Infectious Diseases, Christian Medical College, Vellore, India.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Rupali
authors.affiliation: Department of Microbiology, Christian Medical College, Vellore, India.
authors.forename: Joy S
authors.initials: JS
authors.lastname: Michael
mesh_terms: D057205:Automation, Laboratory; D024881:Drug Resistance, Bacterial / Q000235:genetics; D006801:Humans; D007194:India; D008826:Microbial Sensitivity Tests / Q000379:methods; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D015203:Reproducibility of Results; D012293:Rifampin / Q000627:therapeutic use; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D062606:Tertiary Care Centers; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: D012293:Rifampin
keywords: Xpert MTB/RIF; Xpert MTB/Rif; extrapulmonaire; extrapulmonar; extrapulmonary; tuberculose; tuberculosis