Doctors who own their own outpatient surgery centers perform nearly twice as many surgeries as those who don't, according to a study published this week in Health Affairs.

Using data from a Florida health database listing all outpatient surgeries performed in the state between 2003 and 2005, the researchers found that physician-owners of surgery centers, called surgicenters, performed, typically, hundreds more of one of several common procedures than their non-owning counterparts.

This could be a concern because of the possibility that doctors self-refer more of their patients for surgery if they stand to gain more financially, warns the study's author.

"There is a potential conflict of interest with ownership since physician-owners of a surgery center collect not only their professional fee for the surgical service provided, but also share in the facility's profits," says Dr. John Hollingsworth, a urologist, Robert Wood Johnson Foundation Clinical Scholar at the University of Michigan in Ann Arbor and lead author of the paper.

How the study worked

For the study, the scientists looked at five common outpatient procedures: carpal tunnel surgery, cataract removal, colonoscopy, knee arthroscopy and a chronic ear infection treatment, usually performed on kids, called myringotomy with tympanostomy tube placement.

The researchers chose these procedures because indications "can be a little gray at times," observes Hollingsworth.

"By nature, outpatient surgery is somewhat discretionary. It's different from emergent procedures," he tells DOTmed News.

And to make sure they were comparing similar groups, the researchers had to control for different population features, as patients who saw physician-owners were on average somewhat healthier. But even controlling for that, it seems physician-owners performed 366 more colonoscopies, 204 cataract excisions and 53 knee arthroscopies than non-owning doctors.

In an interesting twist, the researchers also checked to see if physicians who owned surgical centers performed more procedures than in the years before they bought into one. To do this, they tracked physicians who before 1999 didn't own a center, and compared their rate of surgery after they bought into one in 2000. What they found was intriguing: a 50 percent increase in procedures.

Self-referral questions

Under federal provisions passed in the 1990s to limit the exploitation of self-referral, collectively known as the Stark law, physicians are restricted in what types of centers they can own. But there are carve-outs for the surgicenters, also called ambulatory surgical centers.

And physicians have been buying them up. According to the study, between 2000 and 2007, there was a 50 percent increase in the number of Medicare-certified surgicenters, with doctors having a stake in 83 percent of them, and owning outright nearly half.

Hollingsworth says this rise in ownership tracks nicely with the declining real dollar income of doctors.

"If you're trying to maintain your level of income, you have a couple of options," he says. "See more patients, but another source of revenue would be nontraditional: investing in other technologies or other financial arrangements."

Caveats

Still, it's important to note that the current study doesn't say that any of the surgeons were performing unnecessary procedures. Because of the study limitations, the researchers weren't able to look at the actual appropriateness of the procedures ordered, all of which could have been medically required.

Plus, the researchers had to rely on physician identification numbers scrubbed clean of any real identifying data. The researchers therefore couldn't tell if a physician was actually performing on self-referred patients, although Hollingsworth says that aside from some of the GI procedures, most surgeries would have been done by the physician who ordered it.

More seriously, the researchers had to use a proxy for actual ownership. As the physician data they had was anonymous, they couldn't match doctors up with their practices. And even if they could, it might be hard to know if the physician was the owner without serious sleuthing, as current law doesn't require doctors to disclose interests in their outpatient centers, says Hollingsworth.

Instead, Hollingsworth and his colleagues dubbed as "owner" any physician who performed more than 30 percent of the surgeries at the surgicenter.

"We know from federal Safe Harbor [laws] that in order to not be in violation of the federal statute, they need to perform a minimum of one-third [of their surgeries at the center]," he says. "So we empirically defined an owner and who wasn't based on who concentrated their cases at a given surgical center."

Hollingsworth admits there's a possibility for error, which is why they also tested the data using more stringent cut-offs: doctors who performed at least 60 percent of their surgeries at one center were "owners," and those who performed less than 20 percent were "non-owners." And even with this, they were able to find good agreement with the data, Hollingsworth says.

Future studies

But Hollingsworth hopes to clear up these questions with future studies. He says he would like to look at a procedure -- such as surgery for breast cancer -- where there is less wiggle room for ordering, and compare its use by a physician-owner against an elective procedure.

He would also like to answer whether doctor-owners' procedures really differed at all in appropriateness, thereby burdening the health care market with unnecessary costs. For now, though, it's not clear.

"Again, the next phase for us is to look at effectiveness and efficiency," he says. "It's entirely possible that people could be receiving better care at surgery centers."