High Volume Hospitals Not Always the Best
Number of procedures performed doesn't guarantee good results
TUESDAY, Jan. 13, 2004 (HealthDayNews) -- Two new studies of very different medical problems carry the same message: You can't judge the quality of care that a hospital provides simply by counting the number of cases it handles.
One study looks at the association between hospital volume and results for patients having coronary artery bypass surgery. The other measures hospital volume and survival of very low birth weight babies.
Both studies appear in the Jan. 14 issue of the Journal of the American Medical Association. And both come to the same conclusion -- hospital volume is a rough guide to quality of care, but much better indicators are available.
"There is a general relationship [between high volume and quality care] but it is slight," says Dr. Eric D. Peterson, an associate professor of medicine at the Duke Clinical Research Institute and leader of the study on bypass surgery. "If you look at individual centers, many small-volume hospitals had good results and some large centers had poor results."
The heart patient data came from the Society of Thoracic Surgeons' National Cardiac Database, which includes information on 267,089 bypass procedures done at 439 U.S. hospitals in 2000 and 2001. The average number of operations per hospital per year was 253, with 82 percent of the hospitals performing fewer than 500 procedures.
The rate of patient deaths was lower in high-volume hospitals, but not strikingly so -- a reduction of 0.07 percent for every 100 additional procedures performed. And the variation in death rates among hospitals with similar volumes was very large. Closing the 100 lowest-volume centers -- those doing 150 or less procedures -- would prevent only 50 of the 7,110 surgery-related deaths that occurred, the researchers estimate.
"The message for the general public is that you need to look at more than just volume if you want to select a center," Peterson says.
The best quality indicator is a hospital's mortality rate, rather than the number of procedures done, the report says, and "more lives could potentially be saved if patient referrals were based on the former rather than the latter."
However, "there is no one single indicator of a successful outcome," adds Dr. David M. Shahian, chief of cardiac surgery at the Lahey Clinic in Burlington, Mass., who wrote an accompanying editorial in the journal. A key factor should be the recommendations of the patient's primary doctor, he says.
"I would discourage the public from looking at things like hospital rankings," Shahian says. "These are very problematical from a statistical standpoint."
The second study looked at the survival rate of 94,110 infants weighing no more than 53 ounces at birth who were treated in Vermont neonatal intensive care units.
"Historical volume was not significantly related to mortality rates in 1999-2000, implying that volume cannot prospectively identify high-quality providers," says the study by researchers at RAND Corp.
"The message of our paper is that while volume is related a bit to outcome, it is only weakly related," says Doug Staiger, a professor of economics at Dartmouth University and a member of the research team. "Using past survival rates, you can do a lot better at identifying good units. Even among low-volume providers, there is a confusing amount of variation."
Health experts are trying to determine the best guidelines for identifying the better neonatal intensive care units, Staiger says.