title: Rapid molecular testing for TB to guide respiratory isolation in the U.S.: a cost-benefit analysis.
abstract: BACKGROUND
  Respiratory isolation of inpatients during evaluation for TB is a slow and costly process in low-burden settings. Xpert MTB/RIF (Xpert) is a novel molecular test for tuberculosis (TB) that is faster and more sensitive but substantially more expensive than smear microscopy. No previous studies have examined the costs of molecular testing as a replacement for smear microscopy in this setting.
  
  
  METHODS
  We conducted an incremental cost-benefit analysis comparing the use of a single negative Xpert versus two negative sputum smears to release consecutive adult inpatients with presumed TB from respiratory isolation at an urban public hospital in the United States. We estimated all health-system costs and patient outcomes related to Xpert implementation, diagnostic evaluation, isolation, hospitalization, and treatment. We performed sensitivity and probabilistic uncertainty analyses to determine at what threshold the Xpert strategy would become cost-saving.
  
  
  RESULTS
  Among a hypothetical cohort of 234 individuals undergoing evaluation for presumed active TB annually, 6.4% had culture-positive TB. Compared to smear microscopy, Xpert reduced isolation bed utilization from an average of 2.7 to 1.4 days per patient, leading to a 48% reduction in total annual isolation bed usage from 632 to 328 bed-days. Xpert saved an average of $2,278 (95% uncertainty range $1582-4570) per admission, or $533,520 per year, compared with smear microscopy.
  
  
  CONCLUSIONS
  Molecular testing for TB could provide substantial savings to hospitals in high-income countries by reducing respiratory isolation usage and overall length of stay.
authors.affiliation: Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, California, United States of America ; PRIME Residency Program, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Millman
authors.forename: David W
authors.initials: DW
authors.lastname: Dowdy
authors.forename: Cecily R
authors.initials: CR
authors.lastname: Miller
authors.forename: Robert
authors.initials: R
authors.lastname: Brownell
authors.forename: John Z
authors.initials: JZ
authors.lastname: Metcalfe
authors.forename: Adithya
authors.initials: A
authors.lastname: Cattamanchi
authors.forename: J Lucian
authors.initials: JL
authors.lastname: Davis
mesh_terms: D003362:Cost-Benefit Analysis; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics / Q000472:pathogenicity; D010802:Phylogeny; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*; D014481:United States