Physicians often grumble about insurers, but it's rare for doctors to launch a campaign against a particular carrier. Nonetheless, one practice, Physician Associates, has sent letters to its 30,000 patients warning that the group had experienced "serious problems" with CareFirst BlueCross BlueShield and would "with great regret" withdraw from the insurer's network in November. The letter encouraged their 2,500 CareFirst patients to switch their coverage to UnitedHealthcare, Cigna or Alliance, which "have been more responsive to the needs of our patients."

CareFirst -- the largest health insurer in the region -- does not always allow patients to use the highest-quality specialists and has inappropriately applied deductibles to some patients, said Elliot R. Goldstein, a physician at the 13-doctor practice, which has offices in Rockville and Chevy Chase. The doctors also said CareFirst routinely denied some claims by improperly asserting that a patient needed a referral to be treated by a doctor covering for another physician within the practice.

The physicians also said CareFirst inappropriately required deductibles from patients who should not have to pay them -- including those in the BlueChoice health maintenance organization and some federal workers.

However, at least some of the physicians' concerns appear to be unfounded, according to government officials.

"There is no evidence that deductibles were inappropriately applied" to federal workers, said Mike Orenstein, a spokesman for the Office of Personnel Management (OPM). "We reviewed the allegations, and the bottom line is that there is no basis for them."

CareFirst spokesman Jeff Valentine called Goldstein "a disgruntled physician who is making all kinds of allegations that he hasn't backed up." Valentine said the insurer is investigating whether the physicians' concerns are the result of billing errors, but added that "we can't validate the majority of their complaints."

After the physicians issued their Sept. 14 letter to patients, CareFirst officials tried to woo the practice back into its network of 26,000 doctors, according to Valentine. The insurer offered higher payments, but Goldstein said those rates were still lower than his group receives from any other carrier.

Despite the OPM findings, Goldstein said he remained convinced that CareFirst had acted improperly. "If I'm wrong, then I wish someone would tell me how I got it wrong," he said. "I've double-checked and triple-checked this, and the more we study this, the more we believe we're right."

Bruce Edwards, the CareFirst senior vice president of networks management, said, "We dispute the allegations in the Physician Associates letter as reckless, misleading and totally unfounded."

-- Rebecca Adams

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