“The secondary analyses, which were based on hospital ownership, should only be hypothesis-generating in nature as they are both underpowered and prone to selection bias because of limited data availability,” the researchers note.

Dr. Eric K. Wei from NYC Health and Hospitals, in New York, who co-authored a linked commentary, told Reuters Health by email, “Despite our best intentions and without consciously trying to have two standards of care, the data shows that these disparities in care exist. We cannot continue the status quo and expect different results.”

He offered three suggestions that might reduce or eliminate these disparities: “provide EMTALA-like protections to preventative and outpatient care; level the financial playing field for hospitals that provide care to a larger proportion of uninsured and Medicaid patients; [and] create programs that provide universal access to preventative and outpatient care.”

“Public health systems play an important role in providing health care to patients who would otherwise be marginalized in the U.S. health care system,” Dr. Wei concluded.

Dr. Scott M. Dresden from Northwestern University’s Department of Emergency Medicine, in Chicago, who has studied ED use for the uninsured before and after Affordable Care Act Insurance expansion, told Reuters Health by email, “Despite EMTALA, it appears that preferential transfer of ‘lower paying’ patients still happens.”

“I was surprised that after eliminating hospitals without critical care capacities, uninsured and Medicaid patients were still more likely to be transferred,” said Dr. Dresden, who was not involved in the new work. “It could be that these were the more complex patients rather than evidence that hospitals are doing a wallet biopsy prior to admission or transfer decisions; however, these were only hospitals with critical care capacities included in the study.”

“The first step (to addressing these disparities) would be to continue to reduce the number of patients who are uninsured and to increase the Medicaid reimbursement to be equivalent to private insurance,” Dr. Dresden said. “This would take away any financial incentive to diverting patients to different hospitals. Short of that, transfer rates at hospitals should be compared against peer institutions, and those with higher transfer rates for patients who are uninsured or on Medicaid should be investigated.”

Dr. Venkatesh did not respond to a request for comments.