Comparison of Composite Measure Methodologies for Rewarding Quality of Care

Abstract

Composite indices of health care performance are an aggregation of underlying individual performance measures and are increasingly being used to rank hospitals. We sought to conduct an observational analysis to determine the influence of the opportunity-based and all-or-none composite performance measures on hospital rankings. We examined 194 245 patients hospitalized with acute myocardial infarction between July 2006 and June 2009 from 334 hospitals participating in the Get With The Guidelines--Coronary Artery Disease (GWTG-CAD) quality improvement program. We analyzed hospital opportunity-based and all-or-none composite scores and 30-day risk-standardized all-cause mortality and readmission rates. We found that the median calculated opportunity-based score for these hospitals was 95.5 (interquartile range, 90.4, 98.0). The median all-or-none score was 88.9 (interquartile range, 79.7, 94.4). The 2 scoring methods were significantly correlated with one another (r=0.98, P<0.001). Rankings generated by the two methods were significantly correlated (r=0.93, P<0.001). The two methods had a modest correlation with the 30-day risk-standardized mortality rate (opportunity-based score: r=-0.25, P<0.001; all-or-none score: r=-0.24, P<0.001). Neither composite measure correlated with the 30-day risk-standardized readmission rate. Over time, the number of hospitals new to the top and bottom quintiles of hospital rankings diminished similarly for both composite measures. When including additional performance measures into the composite score, the two methods produced similar changes in hospital rankings. The opportunity-based and all-or-none coronary artery disease composite indices are highly correlated and yield similar ranking of the top and bottom quintiles of hospitals. The two methods provide similarly modest correlations with 30-day mortality, but not readmission.