The Public Health Service Commissioned Corps, the federal government's elite 7,000-member medical unit, is being threatened by a scalpel -- the one wielded by David A. Stockman, director of the Office of Management and Budget.

A proposal outlined by Stockman in a March 19 letter to Health and Human Services Secretary Richard S. Schweiker suggested that the corps might be abolished and its personnel transferred to the regular civil service, where pay and fringe benefits are less attractive, especially for doctors.

Stockman spokesman Ed Dale said yesterday that there has been no final decision yet on whether to go ahead with the proposal and that Stockman's letter merely raised the possibility. "We have no intention now of abolishing the corps," Dale said.

But top HHS officials have widely interpreted the March 19 letter as indicating Stockman's desire to abolish the corps.

The corps was established in 1889 as a mobile force of health specialists. About half its members are physicians, the rest nurses and other health professionals.

It is modeled on the Army and its personnel have uniforms, get paid on the same scale as the armed forces and have the same generous retirement scheme.

Its members can be ordered anywhere on the double -- to the deep reaches of Africa of Asia if some nation needs help in stamping out an epidemic, to Three Mile Island in the wake of a nuclear radiation scare, to poorly served areas of the country to care for the sick, to Indian reservations to carry out the nation's Indian health commitment, to Florida for health screening of Cuban and Haitian refugees, to Alaska to care for the state's native population.

President Reagan proposed in his budget the phasing out of eight Public Health Service hospitals manned in part by uniformed commission corps personnel.

Unmentioned in the budget was an added proposal sent to Schweiker in the March 19 letter, a copy of which has been obtained by The Washington Post. It read: "As we agreed during the development of the 1982 budget, your department should develop options, by June 1, 1981, for integrating the PHS Commissioned Corps with the general schedule personnel system. We understand that these options will include detailed implementation plans for integrating the two personnel systems beginning in FY 1982."

Within HHS, there was considerable opposition to the Stockman idea. An internal memo from one high official to three assistant secretaries declared there was a 95 percent probability that crops personnel would lose salary under a merger, and some strong indications that, for a variety of reasons, the switchover wouldn't save any money.

Another memo, signed by some of the top health officials in HHS, urged Schweiker to insist that HHS be allowed to study the matter, come up with its own recommendations and "not be governed by a foregone conclusion that the crops be abolished." Schweiker has the matter under consideration, but said yesterday he has not made a decision yet.

Stockman spokesman Dale said that one reason some believe the corps should be integrated into the regular civil service under the general schedule is that it would make for a better organizational structure. He said many parts of the government have specialized groups doing the same work as people in the general civil service and "in the longer run we might take a look at all these specialized groups." But he said repeatedly that no final decision on the commissioned corps had been made.

William Lucca, executive director of a private organization called the Commissioned Officer Association of the United States Public Health Service, said the great advantage of having a seperate corps is its espirit de corps -- a result of its unique identity, traditions of service and favorable pay and allowances. But even more important, he said, is the fact that it is a highly mobile force that can be rushed to emergencies and sent to difficult areas, sometimes to perform less-than-desirable tasks, with far more ease than can civilian doctors.

Lucca said he is seeking congressional support to block any move along the lines outlined by Stockman's letter.