Patient safety incidents at America's hospitals increased slightly between 2001-2003, but the nation's safest hospitals grew even safer, widening the gap in patient safety incident rates among the nation's best and worst hospitals, according to a new study.

HealthGrades (, an organization that evaluates the quality of hospitals, physicians and nursing homes, based its findings on 37 million patient records.

The second annual "Patient Safety in American Hospitals Study" finds 1.18 million patient safety incidents occurred among Medicare hospitalizations in the years 2001, 2002 and 2003, with the cost to Medicare approaching $3 billion annually. That compares with 1.14 million incidents in the three years beginning with 2000.

The study also finds that hospital-acquired infections grew by 20 percent and accounted for 30 percent of the costs of patient safety incidents.

Hospital-acquired infections correlated most highly with overall performance and performance on the other 12 Patient Safety Indicators identified by the Agency for Healthcare Research and Quality, suggesting that hospital-acquired infection rates could be possibly used as a proxy of overall hospital patient safety.

Patients in the top 10 percent hospitals had, on average, 50 percent lower occurrence of experiencing one or more PSIs compared to patients at the bottom 10 percent hospitals.

Overall, from 2001 through 2003, the best-performing hospitals as a group (hospitals that had the lowest overall PSI incident rates of all hospitals studied, defined as the top 10 percent of all hospitals studied) had 267,151 fewer patient safety incidents and 48,417 fewer deaths resulting in a lower cost of $2.3 billion associated with Medicare beneficiaries as compared to the bottom 10 percent of all hospitals studied.

"The reason we see the hospitals with the lowest incident rates improving the fastest is that they have what I call a 'culture of safety'," said HealthGrades Vice President of Medical Affairs Samantha Collier, M.D., who authored the study. "A 'culture of safety' requires rapid identification of errors and root causes and the successful implementation of improvement strategies, which can only be achieved with strong leadership, critical thinking, and commitment to excellence."

Among the patient safety indicators are: failure to rescue, foreign body left during procedure, post-operative hemorrhage or hematoma, post-operative respiratory failure, and post-operative pulmonary embolism or deep vein thrombosis.