Such challenges may include an educational level that makes it difficult to understand medical issues and treatments, and lack of a strong support system during illness.

Dr. Lee says the study clearly suggests that Medicaid status should be taken into account along with medical and surgical factors when considering whether a surgery is appropriate for a particular patient.

But, he adds, the implications extend to health policy in general.  

"We first wanted to understand complication risk to enhance patient safety and improve quality of care overall. But as we enter a new health care era in which the Medicaid population will expand, we also have to be mindful that medical centers that see a disproportionate number of resource-challenged patients may be financially penalized because of the higher complication rate," he says.  

Dr. Hacquebord adds, "Hospitals are increasingly going to be judged on quality metrics, and it's important to highlight how these ratings may negatively impact care and access for patients."

Gorav Ailawadi, MD, an associate professor of surgery at the University of Virginia in Charlottesville, is familiar with the subject: He co-authored a 2010 study comparing postsurgical complications in nearly 900,000 uninsured, publicly and privately insured patients.

Of the University of Washington study, he says, "I think these findings continue to support our original paper, which identified that Medicaid and uninsured patients had higher complication rates. Another strength of this study was that they used a completely different database than we did and found similar results. Thus it is likely that these are real findings that Medicaid patients do worse. Again this may not be a cause of Medicaid funding but rather the type of patients that need Medicaid."

Patience White, MD, vice president of public health for the Arthritis Foundation and a professor of medicine and pediatrics at The George Washington University School of Medicine and Health Sciences in Washington, DC, says the study raises a number of important issues.

"They do a very good job of discussing potential reasons why Medicaid patients fare so badly," she says. "Certainly, lack of access to services is crucial because a lot of physicians don't accept Medicaid patients. Medicaid reimburses at a lower rate and a lot of doctors are opting out of that. [What's more], when doctors are put on a quality-of-care rating – and this is what is happening now – an unintended consequence is that they won't take on people with the potential for bad outcomes."

Dr. White says the study is also notable for tackling the serious matter of underinsurance. "This is another place to say, 'Wait a minute; there are lots of reasons why people don't do well.”