Much of the shortage of primary care physicians expected over the next decade could be eliminated if the nation increases use of new models of medical care that expand the role of nurse practitioners and physician assistants, according to a new RAND Corporation study.

Expansion of patient-centered medical homes and nurse-managed health centers could help eliminate 50 percent or more of the primary care physician shortage expected to face the U.S. by 2025, according to findings published in the November edition of the journal Health Affairs.

"Growing use of new models of care that depend more on nonphysicians as primary care providers could do much to reduce the nation's looming physician shortage," said David Auerbach, the study's lead author and a policy analyst at RAND, a nonprofit research organization. "But achieving this goal may require changes in policy, such as laws to expand the scope of practice for nurse practitioners and physician assistants, and changes in acceptance, on the part of providers and patients, of new models of care."

Forecasts suggest that as more Americans seek health services once they become newly insured under the Affordable Care Act, physician shortages could worsen. Prominent groups have projected shortages of primary care physicians as high as 45,000 physicians by 2025. Those forecasts do not account for changes in how primary care is delivered, however.

Both patient-centered medical homes and nurse-managed health centers are models of primary care that use a mix of medical providers that is richer in nurse practitioners and physician assistants than today's predominant models of delivering medical care.

Medical homes typically use a team-based approach that incorporates physicians, advance practice nurses, physician assistants, pharmacists, nutritionists and other health professionals. They now account for about 15 percent of primary care nationally.

Nurse-managed health centers provide a full range of primary care and some specialty services. They are managed and operated by nurses, with nurse practitioners functioning as the primary care providers. The clinics now account for only 0.5 percent of primary care and typically are affiliated with an academic health center.

If medical homes expand to deliver nearly half of primary care, the nation's expected physician shortage would fall by 25 percent, according to the RAND study. If nurse-managed health centers expand to account for 5 percent of primary care, the doctor shortage would fall by another 25 percent.

Researchers say those growth rates are plausible under the Affordable Care Act. The use of medical homes has been growing rapidly and the Affordable Care Act provides up to $50 million to support nurse-managed health centers.

But there also are obstacles to wider adoption of the approaches, according to the study. State laws may need to be changed to widen the scope-of-practice for both nurse practitioners and physician assistants so they can fill a wider role in primary care.

In addition, there is a need for medical assistants, licensed practical nurses and aides to perform key functions in the new care models, as well as new payment approaches that reward providers for moving to efficient and effective modes of care.