The number of U.S. hospitals investigated or cited for breaking federal emergency treatment rules has declined over the past decade, a study suggests.

The Emergency Medical Treatment and Labor Act (EMTALA) requires that all patients who come to hospital emergency departments receive a medical screening and any care needed to stabilize their condition, regardless of their ability to pay. Nationwide, 7.2 percent of hospitals were investigated in 2014 for violating the law, down from 10.8 percent in 2005.

Those investigations resulted in citations for 3.2 percent of hospitals in 2014, down from 5.3 percent a decade earlier, the study found.

"We are not completely sure as to why there is a general trend toward fewer investigations and citations," said lead author Dr. Sophie Terp, of the Keck School of Medicine at the University of Southern California in Los Angeles.

"The optimistic view is that emergency departments are increasingly fulfilling their EMTALA obligations and, therefore, fewer complaints are being generated," Terp added by email.

Congress passed EMTALA in 1986 in response to a public outcry over incidents of inadequate, delayed or denied treatment of uninsured patients, researchers note in the Annals of Emergency Medicine.

The intent of the law was ensure all patients access to emergency services and to prevent "patient dumping," the practice of refusing or transferring disadvantaged patients without screening to see what care they might need or stabilizing them before a transfer to another facility.

During the entire study period, there were 4,772 investigations, of which 2,118 resulted in citations for EMTALA deficiencies at 1,498 of the 2,417 hospitals investigated, the study found.

On average, 9 percent of hospitals were investigated and 4.3 percent were cited for violations annually during the study period.

One remaining question is whether the decrease in citations over time represents improved compliance with administrative components of the statute or truly reflects improvement in access to quality of emergency care, Terp said.

That's because citations for administrative lapses like failing to maintain a central log or an on-call list decreased as a proportion of all citations, while the proportion of citations for clinical deficiencies like improper screening and transfer practices increased, Terp noted.

"This raises questions about whether EMTALA actually accomplished its original goals of reducing patient dumping or improving access to quality emergency care," Terp said.

Another limitation of the study is that it may not reflect any patients who are turned away by hospitals that follow the letter of the law, said Dr. David Kao of the University of Colorado School of Medicine, who wasn't involved in the study.

"An example from my past experience would be air-transporting uninsured patients with bleeding from the stomach hundreds of miles (while still bleeding) from one hospital to another where the transferring hospital had more gastroenterologists on staff and performed more endoscopies annually than the accepting hospital, but did not have any of those gastroenterologists assigned as 'on-call'," Kao said by email.

"This does not violate the letter of EMTALA but clearly violates the spirit," Kao added. "This sort of behavior is extremely difficult to report for a number of reasons, including the reluctance on the part of the accepting hospital to damage the relationship with a referral source."

But the declining trend in violations is still encouraging, said Dr. Mark Langdorf, an emergency medicine researcher at the University of California, Irvine, who wasn't involved in the study.

"I think that hospitals and emergency departments are more aware (read afraid) of their EMTALA obligations and comply with the spirit and letter of the law to avoid violations," Langdorf said by email.