Classification of comorbidity in trauma: the reliability of pre-injury ASA physical status classification

Injury. 2013 Jan;44(1):29-35. doi: 10.1016/j.injury.2011.12.024. Epub 2012 Jan 25.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Comorbidity*
  • Female
  • Health Status*
  • Humans
  • Injury Severity Score
  • Male
  • Middle Aged
  • Norway / epidemiology
  • Odds Ratio
  • Reference Standards
  • Registries / standards
  • Registries / statistics & numerical data
  • Reproducibility of Results
  • Surveys and Questionnaires
  • Wounds and Injuries / diagnosis*
  • Wounds and Injuries / epidemiology*