title: Classification of comorbidity in trauma: the reliability of pre-injury ASA physical status classification.
abstract: BACKGROUND
  Pre-injury comorbidities can influence the outcomes of severely injured patients. Pre-injury comorbidity status, graded according to the American Society of Anesthesiologists Physical Status (ASA-PS) classification system, is an independent predictor of survival in trauma patients and is recommended as a comorbidity score in the Utstein Trauma Template for Uniform Reporting of Data. Little is known about the reliability of pre-injury ASA-PS scores. The objective of this study was to examine whether the pre-injury ASA-PS system was a reliable scale for grading comorbidity in trauma patients.
  
  
  METHODS
  Nineteen Norwegian trauma registry coders were invited to participate in a reliability study in which 50 real but anonymised patient medical records were distributed. Reliability was analysed using quadratic weighted kappa (κ(w)) analysis with 95% CI as the primary outcome measure and unweighted kappa (κ) analysis, which included unknown values, as a secondary outcome measure.
  
  
  RESULTS
  Fifteen of the invitees responded to the invitation, and ten participated. We found moderate (κ(w)=0.77 [95% CI: 0.64-0.87]) to substantial (κ(w)=0.95 [95% CI: 0.89-0.99]) rater-against-reference standard reliability using κ(w) and fair (κ=0.46 [95% CI: 0.29-0.64]) to substantial (κ=0.83 [95% CI: 0.68-0.94]) reliability using κ. The inter-rater reliability ranged from moderate (κ(w)=0.66 [95% CI: 0.45-0.81]) to substantial (κ(w)=0.96 [95% CI: 0.88-1.00]) for κ(w) and from slight (κ=0.36 [95% CI: 0.21-0.54]) to moderate (κ=0.75 [95% CI: 0.62-0.89]) for κ.
  
  
  CONCLUSIONS
  The rater-against-reference standard reliability varied from moderate to substantial for the primary outcome measure and from fair to substantial for the secondary outcome measure. The study findings indicate that the pre-injury ASA-PS scale is a reliable score for classifying comorbidity in trauma patients.
authors.affiliation: Department of Research, Norwegian Air Ambulance Foundation, Drøbak, Norway. kjetil.ringdal@norskluftambulanse.no
authors.forename: Kjetil G
authors.initials: KG
authors.lastname: Ringdal
authors.forename: Nils Oddvar
authors.initials: NO
authors.lastname: Skaga
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Steen
authors.forename: Morten
authors.initials: M
authors.lastname: Hestnes
authors.forename: Petter
authors.initials: P
authors.lastname: Laake
authors.forename: J Mary
authors.initials: JM
authors.lastname: Jones
authors.forename: Hans Morten
authors.initials: HM
authors.lastname: Lossius
mesh_terms: D000328:Adult; D015897:Comorbidity; D005260:Female; D006304:Health Status; D006801:Humans; D015601:Injury Severity Score; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D016017:Odds Ratio; D012015:Reference Standards; D012042:Registries / Q000592:standards / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D014947:Wounds and Injuries / Q000175:diagnosis* / Q000453:epidemiology*