Those most likely to benefit from participation in accountable care organizations may face the biggest barriers to enrollment, a new report suggests.

“ACOs are a promising new model for improving care,” lead author Valerie Lewis, Ph.D, said in a release. “But we have to make sure that ACO programs include all Americans, especially vulnerable populations.”

The extent to which clinically at risk or socially disadvantaged individuals — including dually eligible Medicare and Medicaid beneficiaries — benefit from ACOs hinges on where they live, according to the report’s authors.

Participation in an ACO is determined by whether a person’s insurer is affiliated ACO contract and whether healthcare providers in their area have been enrolled in an ACO. The quality of the care delivered by providers also is an indicator of their effectiveness, according to the report

What’s more, medically complex patients, such as the dual eligibles that make up a large segment of nursing home residents, are vulnerable to the practice known as “patient dumping,” which could exclude them from participation.

The report was published in the August issue of Health Affairs.