title: Impact of GeneXpert MTB/RIF assay on triage of respiratory isolation rooms for inpatients with presumed tuberculosis: a hypothetical trial.
abstract: BACKGROUND
  Placing inpatients with presumed active pulmonary tuberculosis in respiratory isolation pending results of serial sputum acid-fast bacilli (AFB) smear microscopy is standard practice in high-income countries. However, this diagnostic strategy is slow and yields few tuberculosis diagnoses. We sought to determine if replacing microscopy with the GeneXpert MTB/RIF (Xpert) nucleic acid amplification assay could reduce testing time and usage of isolation rooms.
  
  
  METHODS
  We prospectively followed inpatients at San Francisco General Hospital undergoing tuberculosis evaluation. We performed smear microscopy and Xpert testing on concentrated sputum, and calculated diagnostic accuracy for both strategies in reference to serial sputum mycobacterial culture. We measured turnaround time for microscopy and estimated hypothetical turnaround times for Xpert on concentrated and unconcentrated sputum. We compared median and total isolation times for microscopy to those estimated for the 2 Xpert strategies.
  
  
  RESULTS
  Among 139 patients with 142 admissions, median age was 54 years (interquartile range [IQR], 43-60 years); 32 (23%) patients were female, and 42 (30%) were HIV seropositive. Serial sputum smear microscopy and a single concentrated sputum Xpert had identical sensitivity (89%; 95% confidence interval [CI], 52%-100%) and similar specificity (99% [95% CI, 96%-100%] vs 100% [95% CI, 97%-100%]). A single concentrated sputum Xpert could have saved a median of 35 hours (IQR, 24-36 hours) in unnecessary isolation compared with microscopy, and a single unconcentrated sputum Xpert, 45 hours (IQR, 35-46 hours).
  
  
  CONCLUSIONS
  Replacing serial sputum smear microscopy with a single sputum Xpert could eliminate most unnecessary isolation for inpatients with presumed tuberculosis, greatly benefiting patients and hospitals.
authors.affiliation: Division of Pulmonary and Critical Care Medicine.
authors.forename: Lelia H
authors.initials: LH
authors.lastname: Chaisson
authors.affiliation: Department of Laboratory Medicine.
authors.forename: Marguerite
authors.initials: M
authors.lastname: Roemer
authors.affiliation: Department of Laboratory Medicine.
authors.forename: David
authors.initials: D
authors.lastname: Cantu
authors.affiliation: Department of Laboratory Medicine.
authors.forename: Barbara
authors.initials: B
authors.lastname: Haller
authors.affiliation: Department of Medicine.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Millman
authors.affiliation: Division of Pulmonary and Critical Care Medicine Department of Medicine Curry International Tuberculosis Center, San Francisco General Hospital, University of California.
authors.forename: Adithya
authors.initials: A
authors.lastname: Cattamanchi
authors.affiliation: Division of Pulmonary and Critical Care Medicine Department of Medicine Curry International Tuberculosis Center, San Francisco General Hospital, University of California.
authors.forename: J Lucian
authors.initials: JL
authors.lastname: Davis
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010356:Patient Isolation; D011933:Reagent Kits, Diagnostic / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014218:Triage; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: D011933:Reagent Kits, Diagnostic
keywords: GeneXpert; infection control; molecular diagnostic techniques; tuberculosis
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