Effect of definition of mortality on hospital profiles

BACKGROUND: Hospitals are ranked based on risk-adjusted measures of postoperative mortality, but definitions differ about which deaths following surgery should be included. OBJECTIVE: To determine whether varying the case definition of deaths following surgery that are included in coronary artery bypass surgery quality assessment affects the identification of outlier hospitals. RESEARCH DESIGN: The study used a prospective cohort design. SUBJECTS: A total of 15,288 patients undergoing coronary artery bypass surgery without other cardiac procedures from October 1993 to March 1996 at all (N = 43) Veterans Affairs hospitals that conduct cardiac surgery. MEASURES: The first measure included any death occurring within 30 days after surgery, regardless of cause, in or out of the hospital (30-day mortality). The second measure included 30-day mortality plus any death occurring 30 days to 6 months after surgery that was judged to be a direct result of a perioperative complication of the surgery (all procedure-related mortality). RESULTS: Hospital performance as assessed by the two different definitions of death varied substantially. The rankings of hospitals differed for 86% (37/43) of hospitals. Twenty-one percent (9/43) changed their quartile of rank and five hospitals changed their outlier status. The correlation of observed-to-expected ratios was high (r = 0.96), but there was disagreement of outlier status (kappa = 0.71). CONCLUSIONS: judgments regarding the quality of a hospital's performance of coronary artery bypass surgery vary depending on the definition of postoperative mortality that is used. Further research is needed to assess what definition is most appropriate to identify quality of care problems.