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Br J Anaesth. 2014 Sep;113(3):424-32. doi: 10.1093/bja/aeu100. Epub 2014 Apr 11.

Reliability of the American Society of Anesthesiologists physical status scale in clinical practice.

Author information

1
Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
2
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.
3
Department of Anesthesia, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada.
4
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.

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.

KEYWORDS:

anaesthesiology; health status; reliability and validity

PMID:
24727705
PMCID:
PMC4136425
DOI:
10.1093/bja/aeu100
[Indexed for MEDLINE]
Free PMC Article

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