Comparing AMI mortality among hospitals in patients 65 years of age and older - Evaluating methods of risk adjustment

Background-Interest in the reporting of risk-adjusted outcomes for patients with acute myocardial infarction is growing. A useful risk-adjustment mode l must balance parsimony and ease of data collection with predictive abilit y. Methods and Results-From our analysis of 82 359 patients greater than or eq ual to 65 years of age admitted with acute myocardial infarction to 2401 ho spitals, we derived a parsimonious model that predicts 30-day mortality. Th e model was validated on a similar group of 78 699 patients from 2386 hospi tals. Of the 73 candidate predictor variables examined, 7 variables describ ing patient characteristics on arrival were selected for inclusion in the f inal model: age, cardiac arrest, anterior or lateral location of myocardial infarction, systolic blood pressure, white blood cell count, serum creatin ine, and congestive heart failure. The area under the receiver-operating ch aracteristic curve for the final model was 0.77 in the derivation cohort an d 0.77 in the validation cohort. The rankings of hospitals by performance ( in deciles) with this model were most similar to a comprehensive 27-variabl e model based on medical chart review and least similar to models based on administrative billing codes. Conclusions-A simple 7-variable risk model performs as well as more complex models in comparing hospital outcomes for acute myocardial infarction. Alt hough there is a continuing need to improve methods of risk adjustment, our results provide a basis for hospitals to develop a simple approach to comp are outcomes.