The agreement means Anthem customers will continue to receive discounted rates at Internal Medicine Associates, a group of 55 primary care physicians and five nurse practitioners.
An existing contract between Anthem and Internal Medicine, or IMA, was set to expire Feb. 25.
The agreement will base reimbursement increases on quality measures, according to a statement posted on the doctor group's Web site on Saturday. Anthem has been pushing participation in its pay-for-performance programs in all its contract negotiations with providers.
"We are pleased that Anthem has recognized our ability to deliver quality outcomes-focused health care to their subscribers," said Dr. Lawrence D. Rink, chairman of board of Internal Medicine Associates. "We look forward to continuing to care for our many patients in south-central Indiana."
The agreement affects Anthem's Blue Traditional, Blue Access PPO and Blue Preferred HMO health insurance plans.
Dr. David Lee, vice president of health care management for Anthem Indiana, said, "The goal of the contract is to provide our customers with access to quality medical care at rates they can afford, while also providing IMA with adequate reimbursement that is tied to positive clinical outcomes."
The doctors had said Anthem's payments have increased 2 percent to 3 percent over the seven years of their existing contract, after adjusting for a larger number of Anthem-insured patients and higher utilization of services.
By contrast, the doctors' costs had gone up 27 percent over the seven years. That's much less than the national rate of medical inflation, they said, which has totaled 47 percent in the last seven years.
A spokesman for Anthem said it was trying to keep costs down for its customers.