Getting bariatric surgery at a “center of excellence” doesn’t mean that patients can be assured that they will avoid serious complications from the weight-loss procedure at the facility, according to a recent study.

Even though facilities that have been accredited as centers of excellence must all meet minimum standards, including performing at least 125 bariatric surgeries annually, the risk of serious problems varied widely among centers, the study found.

“To become accredited, there’s no measure of outcomes, it’s just a process list,” said Dr. Andrew Ibrahim, a research fellow at the University of Michigan Institute for Healthcare Policy and Innovation and the study’s lead author. In addition to minimum case volumes, accredited centers have to have special surgical equipment to handle overweight patients, such as bariatric operating tables and longer laparoscopic instruments.

Insurers typically restrict coverage of bariatric surgery to procedures performed at accredited facilities, however, and nearly 90 percent of bariatric surgeries are performed at a center of excellence.

Bariatric surgery is used to treat people who are severely obese and have not had success with other weight-loss programs. Surgeons use a variety of methods to make the stomach smaller so that less food can be consumed easily.

For this study, researchers analyzed claims data of more than 145,000 patients at 165 bariatric surgery centers of excellence in 12 states from 2010 to 2013. Nationally, the rate of serious complications following surgery — heart attack, kidney failure or blood transfusion, for example — varied widely among the centers, from 0.6 percent at the low end to 10.3 percent at the high end. The rate varied widely within states as well. Nearly 1 in 3 lower-performing hospitals had a higher-performing hospital in the same service area, the study found.

Bariatric surgery has come a long way from the early days when some low-volume centers experienced 30-day mortality rates approaching 10 percent, according to Ibrahim. In this study, 72 patients died in the hospital following surgery — a rate of less than 1 percent among study participants.

However, while accreditation has had an effect on quality and safety, “at the moment, just going to a center that is accredited does not ensure uniform high-quality care for a patient,” Ibrahim said.

The degree of technical skill of the surgeon performing the procedure may affect post-operative outcomes, the study found, as may the degree to which centers follow accepted best practices for bariatric patient care. Neither of those variables is captured in this study.

The organization that accredits bariatric surgery hospitals collects data from hospitals about serious complications, but the data aren’t publicly available, according to the study. So there’s no way for patients to use the data to learn which bariatric center of excellence in their area has the lowest serious complication rates. “Not yet,” Ibrahim said.

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