title: Retrospective observational study of diagnostic accuracy of the Xpert® MTB/RIF assay on fiberoptic bronchoscopy sampling for early diagnosis of smear-negative or sputum-scarce patients with suspected tuberculosis.
abstract: BACKGROUND
  Fiberoptic bronchoscopy (FOB) is a useful diagnosis tool in low-burden countries for patients with suspected pulmonary tuberculosis (TB) who are smear-negative or sputum-scarce. This study sought to determine the accuracy of the Xpert® MTB/RIF (XP) assay using FOB samples.
  
  
  METHODS
  We retrospectively reviewed clinical, radiological, and microbiological characteristics of 175 TB-suspected patients requiring diagnostic FOB (bronchial aspirate or bronchoalveolar lavage) with XP assay. Polymerase chain reaction (PCR) and smear microscopy (SM) performances were first compared to culture, then to the final diagnosis, established based on clinical or radiological evolution when cultures were negative.
  
  
  RESULTS
  Of the total 162 included patients, 30 (18.5%) had a final diagnosis of pulmonary TB, with positive cultures reported in 23. As compared to culture, sensitivity and specificity values were 80.0% and 98.6% for the XP assay, and 25.0% and 95.8% for SM, respectively. As compared to final diagnosis, the corresponding performance values were 60.0% and 100.0% for the XP assay, and 16.7% and 95.5% for SM, respectively. The sensitivity of the XP assay was significantly higher than that of SM in both cases (p=0.003 and p=0.001). Concerning the final diagnosis, both XP assay and culture sensitivities were similar (60% vs. 66.7%). PCR assay enabled pulmonary TB to be diagnosed earlier in 13 more cases, compared to SM.
  
  
  CONCLUSIONS
  Our study has confirmed the clinical benefits provided by XP assay compared to SM for the early diagnosis of suspected pulmonary TB cases requiring FOB, on per procedure samples, especially in a low TB-burden country.
authors.forename: Pierre
authors.initials: P
authors.lastname: Le Palud
authors.forename: Vincent
authors.initials: V
authors.lastname: Cattoir
authors.forename: Brigitte
authors.initials: B
authors.lastname: Malbruny
authors.forename: Romain
authors.initials: R
authors.lastname: Magnier
authors.forename: Karine
authors.initials: K
authors.lastname: Campbell
authors.forename: Youssef
authors.initials: Y
authors.lastname: Oulkhouir
authors.forename: Gérard
authors.initials: G
authors.lastname: Zalcman
authors.affiliation: CHU de Caen, Service de Pneumologie et Oncologie thoracique, Caen, F-14000, France. bergot-e@chu-caen.fr.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bergot
mesh_terms: D000328:Adult; D000368:Aged; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology*; D001999:Bronchoscopy; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008853:Microscopy; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques; D011237:Predictive Value of Tests; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology