A consumer guide designed to help the elderly locate Washington area physicians who accept Medicare assignment rates and billing practices was released yesterday by the Gray Panthers, the activist senior citizens organization, and a coalition of other groups and individuals.

The guide lists an estimated 6,000 doctors according to their specialty, the jurisdiction in which they practice and the percentage of Medicare cases they accepted on assignment in calendar 1980.

"We want people to use the directory to find a physician who will take Medicare assignment," said Frances Klafter, a Gray Panther official who helped compile the guide.

In accepting Medicare assignment on a patient, the physician agrees to accept the payment rate that has been determined by the government to be the "reasonable charge" for services performed for that patient. Medicare then reimburses the physician for 80 percent of the established "reasonable" payment, and the patient is responsible for the rest after satisfying the annual $75 deductible.

When a physician doesn't accept Medicare assignment, the patient becomes responsible for all charges imposed by the physician. He still may be eligible to recover Medicare benefits up to the 80 percent cap. But that cap is for 80 percent of the established "reasonable" fee established by Medicare rather than 80 percent of the physician's actual fee.

At a press conference yesterday, coalition leaders said that the guidebook is an important part of their national campaign to contain health care costs and to defeat administration proposals to reduce Medicare benefits.

". . . we believe that doctors' fees are higher than many Medicare beneficiaries can pay and that access to health care for this group is thus limited," the coalition said in the directory's introductory notes.

Klafter said price shouldn't be the only consideration, however, when consumers seek medical help. "They should inquire if this is the doctor who will best suit their purposes and their needs," she said.

Information in the book is based on actual Medicare claims processed for Washington area physicians and obtained by the Coalition for Reducing Medicare Doctors' Charges from Medicare records under the Freedom of Information Act.

The coalition, which is made up of the Gray Panthers of Metropolitan Washington, 21 other area organizations and more than 50 individuals, has published 2,000 guidebooks for distribution to individuals and groups. Each copy sells for $2--the amount the coalition said it needs to recover the cost of printing, postage and other expenses--and may be ordered from the Gray Panther offices, 755 Eighth St. NW, Washington, D.C. 20001.

The District of Columbia Medical Society declined to comment on the guidebook since officials there hadn't seen it. But Dr. Edward E. Fitzgerald, the society's president, questioned the need for such a guidebook.

"There is a better way to arrive at that information," Fitzgerald said, and that is to ask the doctor's office directly.

Fitzgerald said the doctor's decision typically depends on the patient's financial standing. "If I think there is a question of financial hardship, I take assignment. If I don't feel there is financial hardship, I do not accept assignment. That is the official policy in my office and I have reason to think many others follow the same policy."

According to the coalition's guidebook, 161 Medicare claims from Dr. Fitzgerald's office were processed during 1980. Of that total, 13 percent were cases on assignment. Dr. Fitzgerald said that those numbers appeared to be accurate.

Percentage of cases taken on assignment varied enormously from one physician to another, however. Some took 100 percent assignments; others took none on assignment. Many fell in between those two extremes.