title: Xpert(®) MTB/RIF for detection of Mycobacterium tuberculosis from frozen string and induced sputum sediments.
abstract: Although it is now widely used for tuberculosis (TB) diagnosis, Xpert(®) MTB/RIF availability remains inadequate in low-resource settings. Moreover, its accuracy in testing stored samples from non-expectorating patients has not been evaluated.
  
  
  
  To assess the performance of Xpert in frozen samples of induced sputum (IS) and sputum from string test (ST) from non-expectorating individuals with presumed TB.
  
  
  
  This was a laboratory-based study of 377 ST and IS samples collected between March 2010 and March 2013 at a referral hospital in Uganda. Samples were decontaminated, centrifuged and cultured, and the resultant samples were frozen at -20°C before Xpert evaluation.
  
  
  
  TB was detected in ST and IS samples from 19/163 (11.7%) children and 63/201 (29.4%) adults using culture. Xpert sensitivity in frozen sediments from children was 37.5% (95%CI 8.5-75.5) in ST and 41.7% (95%CI 15.2-72.3) in IS samples, with specificities of respectively 100% (95%CI 94.9-100) and 98.6% (95%CI 92.7-100). In adults, sensitivity was respectively 50% (95%CI 31.3-68.7) and 48.5% (95%CI 30.8-66.4) in ST and IS samples, with specificities of respectively 100% (95%CI 95.5-100) and 98.6% (95%CI 92.4-100).
  
  
  
  Given these results, and particularly the high specificity, the use of Xpert on frozen ST and IS sediment samples from both children and adults is promising.
authors.affiliation: Microbiology Department, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: J
authors.initials: J
authors.lastname: Atwebembeire
authors.affiliation: Microbiology Department, Mbarara University of Science and Technology, Mbarara, Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: P
authors.initials: P
authors.lastname: Orikiriza
authors.affiliation: Epicentre, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Bonnet
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: D
authors.initials: D
authors.lastname: Atwine
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: V
authors.initials: V
authors.lastname: Katawera
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: M
authors.initials: M
authors.lastname: Nansumba
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: D
authors.initials: D
authors.lastname: Nyehangane
authors.affiliation: Microbiology Department, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: J
authors.initials: J
authors.lastname: Bazira
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: J
authors.initials: J
authors.lastname: Mwanga-Amumpaire
authors.affiliation: Microbiology Department, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: F
authors.initials: F
authors.lastname: Byarugaba
authors.affiliation: Microbiology Department, Mbarara University of Science and Technology, Mbarara, Uganda; Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: Y
authors.initials: Y
authors.lastname: Boum
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005615:Freezing; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods*; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology; D014454:Uganda