St. Elizabeths Hospital, the trouble-plagued federal mental institution which serves the poor of the District of Columbia, has regained the accreditation it lost four years ago.

The decision of the Joint Commission on Accreditation of Hospitals -- relayed earlier this week to St. Elizabeths officials -- accomplishes a major goal announced two years ago by then-Secretary of Health, Education and Welfare Joseph Califano.

James Buford, named by Califano to direct the upgrading of the hospital, said it was one step in Califano's plan to transfer a revitalized St. Elizabeths from HEW jurisdiction to operation by the District government.

Hospitals need not be accredited by the JCAH, but recognition by that body -- composed of representatives of the nation's major medical specialty organizations -- lends prestige to an institution and its residency programs.

In 1975, when the Joint Commission survey team visited the sprawling complex of St. Elizabeths' buildings in Southeast Washington, it found 111 deficiencies in the physical plant, hospital management and the care of patients.

The latest JCAH report cites 44 areas still in need of upgrading, Buford said yesterday, but "all . . . are related to construction and renovation." None of the recommendations, he said, are related directly to patient care.

One of the areas which came in for the greatest criticism four years ago was the quality of non-psychiatric medical and surgical care provided to the hospital's patients.

But last September the hospital apparently solved that problem by entering into a $3 million-a-year contract with Georgetown University Medical School to provide medical and surgical services for the patients.

That contract, said Buford, was cited by the latest JCAH survey team as representing a marked improvement in conditions at the hospital.

About the same time last year, Congress granted St. Elizabeths $52 million for general upgrading of its aging physical plant.

Most of that money is going to renovation of buildings and improvement of various safety systems -- such as sprinkler systems -- at the hospital, and those improvements, said Buford, should satisfy the Joint Commission's remaining objections.

The joint commission grants hospitals accreditation for either one or two years, the latter being more difficult to obtain. St. Elizabeths was granted one-year accreditation, but many of the nation's prestigious hospitals and medical schools are in the same category as the Joint Commission attempts to tighten its physical safety and record-keeping requirements.

St. Elizabeths has long been the focus of periodic public outrage, as have many other large public mental hospitals.

The hospital is the subject of an ongoing federal court suit -- filed during the Nixon administration -- aimed not only at forcing the release of patients who can function in the community but also at improving the care of the patients who remain in the facility.

It now has only 1,800 in-patients, down from 2,300 two years ago and 7,000 a decade ago.

The transfer of patients into the community has not been without difficulties, however. Last April 10 women were killed and six others injured when fire swept a group home for St. Elizabeths out-patients on Lamon street NW.

Following that fire, investigators found more than two dozen group homes and boarding homes improperly licensed, or not licensed at all, many of them housing the patients St. Elizabeths had been moving outside its walls as the court had ordered.

There also have been a number of news stories in the last several years about violence by patients at St. Elizabeths and other safety problems at the hospital.