JUDGING HOSPITALS BY SEVERITY-ADJUSTED MORTALITY-RATES - THE INFLUENCE OF THE SEVERITY-ADJUSTMENT METHOD

Objective. This research examined whether judgments about a hospital's risk-adjusted mortality performance are affected by the severity- adj ustment method. Methods. Data came from 100 acute care hospitals natio nwide and 11 880 adults admitted in 1991 for acute myocardial infarcti on. Ten severity measures were used in separate multivariable logistic models predicting in-hospital death. Observed-to-expected death rates and z scores were calculated with each severity measure for each hosp ital. Results. Unadjusted mortality rates for the 100 hospitals ranged from 4.8% to 26.4%. For 32 hospitals, observed mortality rates differ ed significantly-from expected rates for 1 or more, but not for all 10 , severity measures. Agreement between pairs of severity measures on w hether hospitals were flagged as statistical mortality outliers ranged from fair to good. Severity measures based on medical records frequen tly disagreed with measures base on discharge abstracts. Conclusions. Although the 10 severity measures agreed about relative hospital perfo rmance more often than would be expected by chance, assessments of ind ividual hospital mortality rates varied by different severity-adjustme nt methods.