title: Reliability of the American Society of Anesthesiologists physical status scale in clinical practice.
abstract: BACKGROUND
  Previous studies, which relied on hypothetical cases and chart reviews, have questioned the inter-rater reliability of the ASA physical status (ASA-PS) scale. We therefore conducted a retrospective cohort study to evaluate its inter-rater reliability and validity in clinical practice.
  
  
  METHODS
  The cohort included all adult patients (≥18 yr) who underwent elective non-cardiac surgery at a quaternary-care teaching institution in Toronto, Ontario, Canada, from March 2010 to December 2011. We assessed inter-rater reliability by comparing ASA-PS scores assigned at the preoperative assessment clinic vs the operating theatre. We also assessed the validity of the ASA-PS scale by measuring its association with patients' preoperative characteristics and postoperative outcomes.
  
  
  RESULTS
  The cohort included 10 864 patients, of whom 5.5% were classified as ASA I, 42.0% as ASA II, 46.7% as ASA III, and 5.8% as ASA IV. The ASA-PS score had moderate inter-rater reliability (κ 0.61), with 67.0% of patients (n=7279) being assigned to the same ASA-PS class in the clinic and operating theatre, and 98.6% (n=10 712) of paired assessments being within one class of each other. The ASA-PS scale was correlated with patients' age (Spearman's ρ, 0.23), Charlson comorbidity index (ρ=0.24), revised cardiac risk index (ρ=0.40), and hospital length of stay (ρ=0.16). It had moderate ability to predict in-hospital mortality (receiver-operating characteristic curve area 0.69) and cardiac complications (receiver-operating characteristic curve area 0.70).
  
  
  CONCLUSIONS
  Consistent with its inherent subjectivity, the ASA-PS scale has moderate inter-rater reliability in clinical practice. It also demonstrates validity as a marker of patients' preoperative health status.
authors.affiliation: Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Sankar
authors.affiliation: Institute of Health Policy Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Division of Rheumatology, Department of Medicine, Toronto Western Hospital, Mount Sinai Hospital, and University of Toronto, Toronto, Ontario, Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: Johnson
authors.affiliation: Department of Anesthesia, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada.
authors.forename: W S
authors.initials: WS
authors.lastname: Beattie
authors.affiliation: Department of Anesthesia, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Tait
authors.affiliation: Institute of Health Policy Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Department of Anesthesia, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada d.wijeysundera@utoronto.ca.
authors.forename: D N
authors.initials: DN
authors.lastname: Wijeysundera
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000776:Anesthesiology; D015331:Cohort Studies; D005260:Female; D006304:Health Status; D006305:Health Status Indicators; D017052:Hospital Mortality; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009864:Ontario; D011594:Psychometrics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012955:Societies, Medical / Q000592:standards*; D011795:Surveys and Questionnaires; D014481:United States; D055815:Young Adult
keywords: anaesthesiology; health status; reliability and validity
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