GOLDEN, CO – Hospitals rated in the top 5 percent in the nation have a 29 percent lower risk-adjusted mortality rate and are improving their clinical quality at a faster pace than other hospitals, according to a study issued Tuesday.

U.S. hospitals in the top 5 percent – designated as Distinguished Hospitals for Clinical Excellence by the healthcare ratings organization HealthGrades – also had risk-adjusted complication rates that were 9 percent lower than other hospitals.

The HealthGrades "Annual Hospital Quality and Clinical Excellence" study examines patient outcomes at all 5,000 nonfederal hospitals in the country based on 40 million hospitalization records from 2006, 2007 and 2008 obtained from the Centers for Medicare and Medicaid Services.

"This independent study of mortality and complication rates identifies an elite group of hospitals that are setting the benchmark for outstanding patient outcomes," said Rick May, MD, HealthGrades' vice president of clinical excellence research and consulting and an author of the study.

Participation is not voluntary, May said, and no hospital can opt out of being rated. For each hospital, risk-adjusted mortality and complication rates are evaluated across 26 procedures and diagnoses, from heart attack treatment to valve-replacement surgery to total knee replacement.

"What's extraordinary is that these hospitals are not standing still," May said. "In fact, the data show that they are continuing to improve their patient outcomes at a faster rate."

To qualify for the HealthGrades list, hospitals are required to meet minimum thresholds in terms of patient volumes, quality ratings and the range of services provided, May said.

Prior to comparing the in-hospital mortality and complication rates of the nation's hospitals, HealthGrades risk-adjusted the data to compare on equal footing hospitals that treat sicker patients. Hospitals with risk-adjusted mortality and complication rates that scored in the top 5 percent or better nationally – which demonstrates superior overall clinical performance – were then recognized as Distinguished Hospitals for Clinical Excellence.

The 2010 study of Medicare patients also discovered that 36 states have one or more hospitals in the top 5 percent. Delaware has the highest percentage of Distinguished Hospitals for Clinical Excellence at 50 percent of eligible hospitals, followed by Maryland, Minnesota, Florida and Connecticut.

According to May, the study revealed that 150,132 deaths among Medicare patients may have been prevented and 13,104 in-hospital complications among Medicare patients may have been avoided if all hospitals performed at the level of the top 5 percent of hospitals.

Those hospitals also showed greater overall improvement in risk-adjusted mortality from 2006 through 2008, with an average of 13.91 percent improvement versus 10.41 percent improvement for other hospitals.

HealthGrades is an independent healthcare ratings organization providing quality ratings, profiles and cost information on U.S. hospitals, physicians, nursing homes and prescription drugs.