PREDICTING IN-HOSPITAL DEATHS FROM CORONARY-ARTERY BYPASS GRAFT-SURGERY - DO DIFFERENT SEVERITY MEASURES GIVE DIFFERENT PREDICTIONS

OBJECTIVES. Severity-adjusted death rates for coronary artery bypass g raft (CABG) surgery by provider are published throughout the country. Whether five severity measures rated severity differently for identica l patients was examined in this study. METHODS. Two severity measures rate patients using clinical data taken from the first two hospital da ys (MedisGroups, physiology scores); three use diagnoses and other inf ormation coded on standard, computerized hospital discharge abstracts (Disease Staging, Patient Management Categories, all patient refined d iagnosis related groups). The database contained 7,764 coronary artery bypass graft patients from 38 hospitals with 3.2% in-hospital deaths. Logistic regression was performed to predict deaths from age, age squ ared, sex, and severity scores, and c statistics from these regression s were used to indicate model discrimination. Odds ratios of death pre dicted by different severity measures were compared. RESULTS. Code-bas ed measures had better c statistics than clinical measures: all patien t refined diagnosis related groups, c = 0.83 (95% C.I. 0.81, 0.86) ver sus MedisGroups, c = 0.73 (95% C.I. 0.70, 0.76). Code-based measures p redicted very different odds of dying than clinical measures for more than 30% of patients. Diagnosis codes indicting postoperative, life-th reatening conditions may contribute to the superior predictive power o f code-basedmeasures. CONCLUSIONS. Clinical and code-based severity me asures predicted different odds of dying for many coronary artery bypa ss graft patients. Although code-based measures had better statistical performance, this may reflect their reliance on diagnosis codes for l ife-threatening conditions occurring rate in the hospitalization, poss ibly as complications of care. This compromises their utility for draw ing inferences about quality of care based on severity-adjusted corona ry artery bypass graft death rates.