Researchers posing as nonelderly adult patients made nearly 13,000 calls to primary care practices across Pennsylvania, New Jersey and eight other states between fall 2012 and spring of last year.

What they found may provide some comfort amid growing concerns of doctor shortages, especially as more people gain coverage through the Affordable Care Act, potentially straining the health system.

Dr. Karin Rhodes, from the University of Pennsylvania and a lead author on the study published this week in JAMA Internal Medicine, says when researchers said they had insurance, they were able to make an appointment about 85 percent of the time — on the first try, no less.

“Capacity exists. I think this is a very optimistic message,” Rhodes says, adding that researchers were usually able to get scheduled within a week. The median wait in Massachusetts was about two weeks.

Rhodes acknowledges the study did not examine the quality of care received, the accessibility for returning patients or the role of cost in determining patients’ real access to services.

Low-income uninsured face biggest barriers

Rhodes says the overall accessibility documented through the study is encouraging, but it varied based on what type of insurance the researchers claimed they had. Those calling as Medicaid patients were successful getting appointments about 60 percent of the time on the first try, compared to that 85 percent of the “privately insured.” When calling with Medicaid coverage, they only contacted providers listed as accepting Medicaid.

When Rhodes examined other national patient surveys and studies that honed in on community health centers, Rhodes found that Medicaid variation did not significantly impede access to primary care, although people had fewer choices of providers.

Dr. Andrew Bindman and Janet Coffman of the University of California, San Francisco, worry about how this will play out as more people gain Medicaid coverage. In an accompanying editorial, they emphasized that fewer doctors accept Medicaid and those that do only take a limited number of patients.

“Safety-net clinics provide a disproportionate amount of care to patients covered by Medicaid, which helps fill some of the void, but this approach is insufficient on its own, particularly for meeting the needs for specialty care,” they wrote.

Beyond those with Medicaid and the privately insured, availability dropped for those who said they were uninsured and couldn’t pay much out of pocket. Researchers were four times less likely to get in compared with those calling with Medicaid.

New primary care models helping alleviate demand

Rhodes says the study provides “a baseline” for tracking primary care access better, and that it will be important to monitor changes as more people gain coverage under the Affordable Care Act. The law includes an expansion of Medicaid in about half of the states.

Massachusetts providers reported being overwhelmed when the state expanded coverage in 2006, but Rhodes points out that nationwide, it has the highest percentage of its population — more than 90 percent — reporting to have a regular source of care.

As for doctor shortages in years to come, national surveys point to the problems growing but perhaps not as dire as the doomsday predictions. Christiane Mitchell, federal policy director with the Association of American Medical Colleges, says physician shortages are of real concern, with projections in primary care falling short by about 45,000 doctors by 2020. At the same time, she says changing approaches are helping to alleviate the growing demands.

“There are new models that use different types of providers that are not physicians,” Mitchell said, including more reliance re on nurse practitioners and team approaches to care. “And there are new payment systems that make sure primary care physicians feel that they’re being paid appropriately.”

Mitchell says Massachusetts is a prime example of making such changes and handling an influx of patients better. The Affordable Care Act also incorporates some of these policies.

Researcher Rhodes  says given the available capacity, helping patients navigate the current system and find accessible practices based on their insurance situation will be especially important in the coming months and years, as will monitoring the availability, affordability and quality of care as more people gain coverage.

“The is just one piece of the elephant,” Rhodes said. “But I think this is an important piece, to get the patient experience when they call up.”