Readmission, mortality rates not statistically linked

In a study that included data on nearly 3 million hospital admissions for Medicare beneficiaries with myocardial infarction, pneumonia or heart failure, researchers failed to find evidence of either a direct or inverse statistical association between a hospital’s performance on the measure for 30-day mortality rates and performance on 30-day readmission rates.

The findings may lessen concerns that hospitals with lower mortality rates will have higher readmission rates, researchers noted in the Feb. 13 issue of the Journal of the American Medical Association.

In background information for the study, the researchers noted that the Centers for Medicare & Medicaid Services began publicly reporting hospital 30-day, all-cause, risk-standardized mortality rates for patients with acute MI and heart failure in 2007, and for pneumonia the following year. In 2009, CMS expanded public reporting to include readmission rates for patients with the three conditions. “The mortality and readmission measures have been proposed for use in federal programs to modify hospital payments based on performance.”

Some researchers have raised concerns that these rates might have an inverse relationship, meaning hospitals with lower mortality rates are more likely to have higher readmission rates. “Interventions that improve mortality might also increase readmission rates by resulting in a higher-risk group being discharged from the hospital,” the researchers wrote in the JAMA article. “Conversely, the measures could provide redundant information. … Limited information exists about this relationship, an understanding of which is critical to measurement of quality, and yet questions surrounding an inverse relationship have led to public concerns about the measures.”

To investigate the issue, Harlan M. Krumholz, MD, SM, of the Yale University School of Medicine in New Haven, Conn., and colleagues examined the relationship between hospital risk-standardized mortality rates and risk-standardized readmission rates overall and within subgroups defined by hospital characteristics.

The study included Medicare fee-for-service beneficiaries discharged between July 2005 and June 2008. For AMI, the sample for final analysis consisted of 4,506 hospitals with 590,809 admissions for mortality and 586,027 readmissions; for HF, 4,767 hospitals with 1,161,179 admissions for mortality and 1,430,030 readmissions; and for pneumonia, 4,811 hospitals with 1,225,366 admissions for mortality and 1,297,031 readmissions.

The researchers found that average risk-standardized mortality rates and risk-standardized readmission rates, respectively, were 16.6% and 19.94% for MI, 11.17% and 24.56% for heart failure and 11.64% and 18.22% for pneumonia.

“For AMI and pneumonia, there was no discernible relationship” between mortality rates and readmission rates, using weighted correlations, the researchers wrote. “For HF, the relationship was only modest and not throughout the entire range of performance.” A high negative correlation would have indicated that doing well on the mortality or readmission measure was linked to doing poorly on the other.

The findings “indicate that many institutions do well on mortality and readmission and that performance on one does not dictate performance on the other,” the researchers concluded.

The study abstract is available at

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