A University of Pennsylvania study in which callers posed as mothers seeking pediatric specialty care found that two-thirds of publicly insured children were refused a doctor's appointment, compared with only 11 percent of privately insured children.

Even the low-income children who were not rejected had to wait an average of 42 days for appointments for urgent conditions such as diabetes, seizures, asthma, or a bone fracture - 22 days longer on average than children with private insurance.

"I was disturbed to find this level of disparity," said senior author Karin V. Rhodes, a Penn emergency-medicine physician and health-policy researcher.

The study was commissioned by state officials in Illinois and conducted in the Chicago area. But the authors and other experts say it adds to evidence that the 37 million children covered by Medicaid and the Children's Health Insurance Program (CHIP) too often face discrimination from providers.

The study also has implications for the Affordable Care Act, the federal law that aims to expand coverage to 32 million uninsured people by 2014. Half are expected to be covered by Medicaid.

Policies and incentives "that encourage providers to accept patients with public insurance are needed to improve access to care," Rhodes and Joanna Bisgaier wrote in Thursday's New England Journal of Medicine.

Some barriers to access, such as reimbursement rates, are well-known. In Illinois, the authors noted, an office visit for a moderately severe problem is reimbursed $99.86 by Medicaid-CHIP, compared with $160 by a commercial health plan.

Low-income patients also have more problems with transportation, communication, and day care.

"They may be seen as noncompliant, or more likely to cancel or not show for an appointment," said Ann Bacharach, special projects director at the Pennsylvania Health Law Project, an advocacy organization. "But they lead more chaotic lives. It's hard to take four kids on two buses to get one child to a doctor. And it's a matter of priorities: Do I keep my child's well-child visit, or pay the electric bill?"

The new study involved methods traditionally used to expose discrimination in housing and labor markets. Posing as mothers and using standardized scripts, graduate students called pediatric specialty clinics for appointments, saying they had referrals from primary-care doctors or emergency rooms. A month later, the same graduate students called the same clinics with the same requests. The only difference was the insurance status - private vs. Medicaid or CHIP. (The state even created fake Medicaid-CHIP identification numbers for the pretend members.)

Callers who obtained appointments canceled at the end of the call.

In total, the students made 546 paired calls to 273 clinics in eight specialties - including dermatology, neurology, and orthopedics - all in Cook County.

A populous urban county with 5.2 million residents, Cook has lots of specialists - 218 per 100,000 people, compared with the national median of 32 per 100,000.

The deceptive design, approved by two ethics boards, enabled the researchers to be sure that appointment denials were not because of patient-related issues such as transportation.

"I don't think this is any surprise," said Villanova University Law School professor Michael Campbell, who cofounded the Pennsylvania Health Law Project. "I don't think anybody doubts that the poor have reduced access to health care generally. It's been that way from day one of Medicaid in the 1960s."

There are, however, differences between state programs that may affect access.

In Pennsylvania, for example, CHIP and Medicaid are managed-care plans, meaning patients see primary-care doctors who serve as gatekeepers to a designated network of specialists.

Illinois in 2006 adopted a "medical home" care model. Medical clinics that provide basic care for Medicaid patients are working to improve coordination and communication with hospitals, specialists, and even dental practices.

Mike Claffey, a spokesman for the Illinois Department of Healthcare and Family Services, said in an e-mail that the new study provided data that would help ongoing efforts to bolster Medicaid care.

"We are studying new service delivery models, as well as new payment systems that provide an incentive for better quality outcomes," he e-mailed.

Staff writer Marie McCullough can be reached at 215 854-2720 or mmcullough@phillynews.com.