Quality varies widely at U.S. centers of excellence for bariatric surgery, with serious complication rates of less than 1% at some places and more than 10% at others, a new study suggests.

Researchers examined rates of serious complications within 30 days of weight loss operations for 145,527 patients at 165 bariatric centers of excellence in 12 U.S. states.

Wisconsin had the least amount of variation among facilities in complication rates, which ranged from 1.5% to 3.3%, researchers report in JAMA Surgery, online April 26. Nebraska had the most variety, with complication rates ranging from 1% to 10.3%.

Often, surgery centers with higher complication rates were close to other centers with lower complication rates, the study also found.

“Patients are likely unaware of the variation,” said lead study author Dr. Andrew Ibrahim of the University of Michigan in Ann Arbor.

“In fact, many surgeons may be surprised by the findings,” Ibrahim said by email.

Before there were any centers of excellence, or even basic accreditation programs for bariatric surgery, death rates were as high as 9% in some centers that didn’t do a huge number of these operations each year, researchers note.

In a push to improve quality and curb death and complication rates, the American College of Surgeons and the American Society for Metabolic and Bariatric Surgery combined their two separate accreditation programs into a single nationwide program in 2012.

This set out uniform criteria for centers of excellence for bariatric surgery. Among other things, qualifying hospitals have to do a certain number of these operations each year and use special operating tables and equipment for bariatric patients.

For the current study, researchers analyzed complication rates from 2010 to 2013 at bariatric centers of excellence in Arizona, Florida, Iowa, Massachusetts, Maryland, North Carolina, Nebraska, New Jersey, New York, Washington and Wisconsin.

They focused on serious complications like bleeding, heart and lung problems, organ injury, wound infections and repeat operations.

Patients in the study were around 47 years old on average and most of them were white and female. In addition to obesity, many of them had other health problems like hypertension, diabetes, depression and lung disease. More than half of them had laparoscopic Roux–en–Y gastric bypass.

Nearly all of the bariatric centers of excellence in the study were in urban areas, and about 71% were based at teaching hospitals.

When researchers grouped hospitals with similar complication rates, they found 28% of the centers had at least one nearby facility with lower complication rates.

Volume, or the number of surgeries done at each center, didn’t appear to influence complication rates at the low end of the spectrum. The lowest complications rates seen were about 0.6% at high–, medium– and low–volume facilities.

But the highest complication rates seen, 10.3%, were at medium–volume centers, compared to 6.4% at low–volume centers and under 5% at high–volume centers.

One limitation of the study is that researchers lacked data on individual surgeons, Ibrahim said.

“We think a large part of the variation may be explained by the skill of the surgeon and care they receive after surgery,” Ibrahim said.

The findings suggest that while bariatric surgery is much safer now than it was a decade ago, just accrediting centers of excellence may not be enough on its own to guarantee high quality care, said Dr. Rajesh Aggarwal, author of an accompanying editorial and researcher at McGill University in Canada.

“There is still more improvement work to be done, and we cannot sit on our laurels,” Aggarwal said by email.

—Lisa Rapaport