While freestanding emergency departments (EDs) are becoming more popular, regulations and requirements on these facilities vary widely between states, which may lead to facilities being built where they’re not needed.

The study, published in the October issue of Health Affairs and led by Catherine Gutierrez, a Harvard University medical student, identified 400 freestanding EDs in 32 states as of December 2015, with the highest concentration in Texas and Ohio. Based on 2013 figures, there were 4,147 hospital EDs in the U.S.

Researchers found little consistency between states when it came to regulating freestanding EDs. Overall, 21 states had regulations specifically dealing with these facilities. Twenty-nine states didn’t, though New York and Washington dealt with freestanding EDs on a case-by-case basis. California was unique in indirectly banning the facilities within its hospital regulations.

A lack of regulation seemed to correlate to more freestanding EDs, which could mean they’re being built in areas where acute care is already readily available. Overall, 24 states required a certificate of need for building one. The study found that in the 32 states with freestanding EDs, those with certificate-of-need requirements had “significantly fewer” freestanding EDs per capita.

“Certificate-of-need requirements have the potential to be beneficial by limiting growth of freestanding EDs in locations with adequate emergency services and by holding down healthcare costs,” Gutierrez and her coauthors wrote. “However, they also have the potential to inhibit the growth of freestanding EDs in areas with inadequate emergency care, where the EDs could improve health care quality.”

Who these facilities have to serve can also vary from state to state. Independent freestanding EDs aren’t subject to the Emergency Medical Treatment and Labor Act (EMTALA). While 18 states do hold these facilities to the same standard in banning them from turning away patients, the 10 freestanding EDs in Arizona, Delaware and Minnesota don’t.

“Without state-specific regulations addressing this obligation or requiring EMTALA-like protections, the growth of independent freestanding EDs has the potential to create a parallel system of emergency care in which people can be turned away based on their insurance status, age, immigration status or other factors,” Gutierrez and her coauthors wrote.

Uneven and outdated regulations also appeared to be a problem, according to the study. For example, though fewer than 2 percent of freestanding ED patients needed transport, two states required the facilities to have a helipad. In Mississippi, freestanding EDs are required to have supplies for peritoneal lavage and pneumatic antishock garments, both of which have been abandoned years ago.

Gutierrez and her coauthors conclude by saying current policies encourage these facilities to be built based on how loose regulations are, rather than where they can improve care.

“Based on current state laws and regulations, we expect growth in freestanding EDs to be limited to 35 states and to be highly concentrated in the 26 states without certificate-of-need requirements,” Gutierrez and her coauthors wrote. “We also anticipate that the current patchwork of state regulations regarding opening and operating freestanding EDs will lead to an oversupply of them in states with few or no regulations and fewer of them in states with restrictions or regulations.”