Hospital Quality for AMI: Process Measures and Their Relationship with Short-term Mortality
Bradley EH, Herrin J, Elbel B, et al. Hospital quality for acute myocardial infarction: correlation among process measures and relationship with short-term mortality. JAMA. 2006 Jul 5;296(1):72-78.
The Centers for Medicare and Medicaid Services (CMS) and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) monitor and publicly report hospital performance in the treatment of acute myocardial infarction (AMI). Core process measures are considered an indicator of quality of care, but little is known about how these measures affect outcomes (mortality). Five of the seven core measures for AMI assess medication prescription practices; the other two measures are counseling on smoking cessation and timely reperfusion therapy.
Inferences about a hospital’s quality of care for AMI are created by measuring the hospital’s success at performing these measures. No previous study had evaluated a possible correlation between performance on these measures and short-term mortality. The authors of this study used National Registry of Myocardial Infarction (NRMI) and CMS databases to determine the association between hospital performance on AMI process measures and hospital-specific, risk-standardized, 30-day mortality rates.
A cross-sectional study was performed using hospitals that reported AMI discharges to the NRMI from January 2002 through March 2003. Hospitals had to report a minimum of 10 eligible patients. Hospital performance on core measures was recorded: beta-blocker on admission, beta-blocker on dismissal, aspirin on admission, aspirin on dismissal, angiotensin-converting enzyme inhibitor (ACE) prescription on dismissal, smoking cessation counseling for smokers during admission, and time to reperfusion therapy. Risk-standardized, 30-day, all-cause mortality rates were calculated for each hospital using CMS Medicare claims for patients ages 66 and older with AMI. The primary analysis determined the association of hospital-specific, risk-standardized, 30-day mortality rates with hospital performance on the core process measures.
The most successfully completed core process measure for AMI was aspirin on admission. A mean of 86.4% of participating hospitals completed this measure. The core process measure for AMI that was the least frequently documented was smoking cessation counseling; a mean of 13.9% of participating hospitals completed this measure. Notably, timely reperfusion therapy for AMI—fibrinolytic therapy within 30 minutes of arrival or percutaneous intervention within 120 minutes of arrival—was completed by only 54.5% (mean) of participating hospitals.
Each core process measure had a statistically significant but small correlation with the risk-standardized, 30-day mortality rate (explaining between 0.1% and 3.3% of variance in mortality). Of the 180 hospitals in the top quintile of risk-standardized, 30-day mortality rates, only 31% were in the top quintile of the core process measures. A composite model of all seven core process measures determined that these measures could only explain 6% of the hospital-level variation in risk-standardized, 30-day mortality rates. Secondary analyses did not differ substantially.
In this study, each core process measure for AMI showed a modest correlation with 30-day mortality, but accounted for only 6% of 30-day mortality. This finding highlights the fact that continued measurement of these processes is valuable, but a hospital’s short-term mortality rates for AMI cannot be reliably inferred from performance on publicly reported process measures. These measures are weighted more toward long-term outcome measures. There is a need for new research to define and study new AMI process measures that can explain more of the variance in both short- and long-term outcomes.