Evaluating alternative risk-adjustment strategies for surgery.

ABSTRACT

BACKGROUND: Comparison of institutional health care outcomes requires risk adjustment. Risk-adjustment methodology may influence the results of such comparisons. METHODS: We compared 3 risk-adjustment methodologies used to assess the quality of surgical care. Nurse reviewers abstracted data from a continuous sample of 2,167 surgical patients at 3 academic institutions. One risk adjustor was based on medical record data (National Surgical Quality Improvement Program [NSQIP]) whereas the other 2, the DxCG and Charlson Comorbidity Index (CCI), primarily used International Classification of Disease-9 (ICD-9) codes. Risk-assessment scores from the 3 systems were compared with each other and with mortality. RESULTS: Substantial disagreement was found in the risk assessment calculated by the 3 methodologies. Although there was a weak association between the CCI and DxCG, neither correlated well with the NSQIP. The NSQIP was best able to predict mortality, followed by the DxCG and CCI. CONCLUSION: In surgical patients, different risk-adjustment methodologies afford divergent estimates of mortality risk.