Hospital quality for acute myocardial infarction: correlation among process measures and relationship with short-term mortality

Abstract

Context: The Centers for Medicare & Medicaid Services (CMS) and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) measure and report quality process measures for acute myocardial infarction (AMI), but little is known about how these measures are correlated with each other and the degree to which inferences about a hospital's outcomes can be made from its performance on publicly reported processes.

Objective: To determine correlations among AMI core process measures and the degree to which they explain the variation in hospital-specific, risk-standardized, 30-day mortality rates.

Design, setting, and participants: We assessed hospital performance in the CMS/JCAHO AMI core process measures using 2002-2003 data from 962 hospitals participating in the National Registry of Myocardial Infarction (NRMI) and correlated these measures with each other and with hospital-level, risk-standardized, 30-day mortality rates derived from Medicare claims data.

Main outcome measures: Hospital performance on AMI core measures; hospital-specific, risk-standardized, 30-day mortality rates for AMI patients aged 66 years or older.

Results: We found moderately strong correlations (correlation coefficients > or =0.40; P values <.001) for all pairwise comparisons between beta-blocker use at admission and discharge, aspirin use at admission and discharge, and angiotensin-converting enzyme inhibitor use, and weaker, but statistically significant, correlations between these medication measures and smoking cessation counseling and time to reperfusion therapy measures (correlation coefficients <0.40; P values <.001). Some process measures were significantly correlated with risk-standardized, 30-day mortality rates (P values <.001) but together explained only 6.0% of hospital-level variation in risk-standardized, 30-day mortality rates for patients with AMI.

Conclusions: The publicly reported AMI process measures capture a small proportion of the variation in hospitals' risk-standardized short-term mortality rates. Multiple measures that reflect a variety of processes and also outcomes, such as risk-standardized mortality rates, are needed to more fully characterize hospital performance.