Allied Physicians Group, a Melville-based network of 37 physician locations, has named Dr. Kerry Frommer Fierstein its new chief executive.

She had been the network’s chief medical officer.

Frommer Fierstein, 54, replaces Dr. Gary Mirkin, who stepped down after 11 years as chief executive. Mirkin, 59, was named president of Allied’s board.

Alliedlaunched 11 years ago when 13 practices teamed up to share resources and costs. Frommer Fierstein’s practice, Plainview-based Pediatric Health Associates, joined in late 2011.

Allied has 22 pediatric offices and four on Long Island for specialties, including allergy, behavioral medicine and breast-feeding practices. The rest of its offices are elsewhere in New York State.

Frommer Fierstein said merging into the Allied network helps medical offices save money on human resources and electronic medical records.

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“We also negotiate contracts with insurers,” she said. “Before our practice merged, we didn’t have access to the insurers that we have now as part of Allied.”

The group is owned by the 70 doctors who operate the member practices.

The costs of being independent have pushed medical practices to join groups like Allied, although many also choose to fold into giant hospital groups.

About 38 percent of physicians nationwide were employed by hospitals in 2015, up from 26 percent in 2012, according to a Physicians Advocacy Institute survey compiled by Avalere Health, a Washington-based health care consultant.

Hospitals acquire physicians’ practices to lock in a patient base, said Kelly Kenney, chief executive at the Raleigh, North Carolina-based institute, which promotes physician causes nationwide.

“Once you get the patient in the family, they generally stay,” Kenney said.

However, some doctors prefer smaller groups like Allied because there is more independence, Kenney said.

Allied has 142 doctors, nurse practitioners and physician assistants. It has about 640 employees.

Frommer Fierstein said she plans to continue to see patients at her Plainview practice three days a week, “and I’ll do my share of weekends as well.”

She also said the group would continue to focus on its charitable foundation, which promotes a literacy program and runs a diaper bank.

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“I can’t imagine having to think twice about changing a diaper because you can’t afford them,” Frommer Fierstein said.

Allied also awards an annual scholarship to one medical student at the Hofstra Northwell School of Medicine. The scholarship is named after Frommer Fierstein’s son, Andrew Fierstein, who died of cancer at age 20 in 2015.

Andrew had been accepted to a Hofstra program that would have led him through an undergraduate and medical degree in eight years.