Risk adjustment of the postoperative morbidity rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study

J Am Coll Surg. 1997 Oct;185(4):328-40.


Background: The National Veterans Affairs Surgical Risk Study was designed to collect reliable, valid data on patient risk and outcomes for major surgery in the Veterans Health Administration and to report comparative risk-adjusted postoperative mortality and morbidity rates for surgical services in the Veterans Health Administration.

Study design: This was a cohort study conducted at 44 Veterans Affairs Medical Centers closely affiliated with university medical centers. Included were 87,078 major noncardiac operations performed under general, spinal, or epidural anesthesia between October 1, 1991, and December 31, 1993. The main outcomes measures in this report are 21 postoperative adverse events (morbidities) occurring within 30 days after the index procedure. Multivariable logistic regression risk-adjustment models for all operations and for eight surgical subspecialties were developed.

Results: Patient risk factors predictive of postoperative morbidity included serum albumin level, American Society of Anesthesia class, the complexity of the operation, and 17 other preoperative risk variables. Wide variation in the unadjusted rates of one or more postoperative morbidities for all operations was observed across the 44 hospitals (7.4-28.4%). Risk-adjusted observed-to-expected ratios ranged from 0.49 to 1.46. The Spearman rank order correlation between the ranking of the hospitals based on unadjusted morbidity rates and risk-adjusted observed-to-expected ratios for all operations was 0.87. There was little or no correlation between the rank order of the hospitals by risk-adjusted morbidity and risk-adjusted mortality.

Conclusions: The Department of Veterans Affairs has successfully implemented a system for the prospective collection and comparative reporting of postoperative mortality and morbidity rates after major noncardiac operations. Risk adjustment had only a modest effect on the rank order of the hospitals.

Publication types

  • Multicenter Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Female
  • Hospital Mortality*
  • Hospitals, Veterans / standards*
  • Hospitals, Veterans / statistics & numerical data
  • Humans
  • Male
  • Middle Aged
  • Models, Statistical
  • Outcome Assessment, Health Care / methods*
  • Quality Indicators, Health Care*
  • Risk Assessment
  • Surgical Procedures, Operative / mortality*
  • Surgical Procedures, Operative / standards
  • United States / epidemiology
  • United States Department of Veterans Affairs