Review of the ASA Physical Status Classification: Comment

We read with interest the review of the American Society of Anesthesiologists (ASA; Schaumburg, Illinois) Physical Status Classification System by Horvath et al.¹  The authors provided an overview of the ASA Physical Status system; however, one use of the ASA Physical Status system is not mentioned that we believe warrants attention due to its impact on hospital finances and quality ratings.

The ASA Physical Status score is a key variable in mathematical models used by the Centers for Disease Control and Prevention (Atlanta, Georgia) National Healthcare Safety Network to risk-adjust surgical site infection rates at U.S. acute care hospitals.²  For each hospital, a standardized infection ratio is calculated for colon surgery and abdominal hysterectomy. The standardized infection ratio is calculated by dividing the observed number of infections for each procedure by the expected number of infections. A standardized infection ratio greater than 1 indicates better than expected performance, whereas a standardized infection ratio less than 1 indicates worse than expected performance. The probability of infection for each patient is calculated using logistic regression equations that incorporate patient, procedural, and facility factors that have been found to predict surgical site infection incidence (table 1). The total number of expected infections is equal to the sum of the probabilities for all patients over a given period.²  The ASA Physical Status score is the only variable that is subjective and therefore prone to misclassification. Systematic underreporting of ASA Physical Status will adversely impact a hospital’s risk-adjusted surgical site infection performance, whereas overreporting (up-coding) will artificially improve a hospital’s performance.

The surgical site infection standardized infection ratio is an important quality metric with both financial and reputational implications for hospitals. It is one of six quality measures evaluated by the Centers for Medicare & Medicaid Services (Baltimore, Maryland) for the Healthcare Acquired Conditions Reduction Program, through which the bottom 25% of hospitals are penalized 1% of their Medicare inpatient revenue.³  Surgical site infection rates also constitute two of the six measures in the safety domain of the Centers for Medicare & Medicaid Services Hospital Value-Based Purchasing Program, which places another 2% of Medicare revenue at risk and provides bonuses to high- performing hospitals.⁴  Moreover, surgical site infection performance is reported by the Leapfrog Group (Washington, D.C.),⁵  displayed on the Centers for Medicare & Medicaid Services Care Compare website,⁶  and incorporated into calculations for Centers for Medicare & Medicaid Services Overall Hospital Quality Star Ratings.⁷  Each of these programs uses the Centers for Disease Control and Prevention National Healthcare Safety Network standardized infection ratios for colon surgery and abdominal hysterectomy; thus, ASA Physical Status misclassification by anesthesiologists will impact hospital performance across these programs.

Dr. Flynn is a Medical Advisor for Psychable, Inc. (Hawthorne, California), a privately held company, and owns shares in MedCrypt, Inc. (Encinitas, California), a privately held company. Dr. Grant is the principal investigator on an institutionally funded research grant from SPR Therapeutics (Cleveland, Ohio), receives royalty payments from Oxford University Press (Oxford, United Kingdom), serves on the Board of Directors of the American Society for Regional Anesthesia and Pain Medicine (Pittsburgh, Pennsylvania), and previously served on the Advisory Board for B. Braun Medical, Inc. (Bethlehem, Pennsylvania). Dr. Lund declares no competing interests.