The busiest hospitals are not necessarily better at saving lives than hospitals with fewer patients, two studies on mortality rates among premature infants and heart surgery patients said on Tuesday.
The studies cast doubt on previous research recommending that people seek out hospitals with the highest volume of patients for some treatments because they are likely to be well equipped and have experienced staff.
Rating a hospital on its success in treating premature infants rather than on the volume of babies treated was found to be more effective in a RAND Corp. study of 332 U.S. hospitals covering 1995 to 2000.
"The number of cases treated by an individual hospital was not a very good predictor of which hospitals would have the best results," said study author Jeanette Rogowski of the Santa Monica, California, based research group.
A second study of 267,000 coronary heart bypass surgeries performed at 439 U.S. hospitals in 2000 and 2001 found patient volume to be a downright poor predictor of mortality rates, especially among patients younger than 65.
"There were many low-volume hospitals with low mortality rates and some high-volume centers with rates higher than expected," wrote study author Eric Peterson of the Duke Clinical Research Institute in Durham, North Carolina.
In the study, more than four out of five hospitals surveyed performed fewer than 500 such surgeries a year, with an average of 253 and an overall mortality rate of 2.7 percent. For every 100 additional surgeries performed, the mortality rate fell just 0.07 percent.
"While the association between volume and outcome was statistically significant overall, this association was not observed in patients younger than 65 years or in those at low operative risk," the report said.
Both studies appeared in this week's issue of the Journal of the American Medical Association.