Thousands of persons with severe blood disease may have their lives extended by a new kind of blood transfusion, that gives them only young, long-lasting red cells.

Thirteen patients at Boston Children's Hospital and one at the National Institutes of Health in Bethesda are already getting the transfusions.

All have thalassemia, also known as Cooley's anemia, a blood disorder of people of Greek and Italian descent.

Within a year NIH doctors hope to be treating eight more thalassemia patients. Next month Boston doctor expect to start treating five patients -- mainly children -- with severe sickle cell anemia, a disease that affects one black in 400.

Hospitals in Chicago, Pittsburgh and Oakland are about to begin treatment programs, and "soon there will be many others," Dr. Richard Propper of Boston Children's predicted yesterday.

Among other patients who could benefit are those who need regular transfusions for leukemia, for some lymphomas -- lymph system cancers -- of for other forms of anemia, especially deadly aplastic anemia.

In all these, the new method could cut in half the number of transfusions a patient needs.

"The big problem in repeated transfusions is building of iron in the body," NIH's Dr. Harvey Klein said yesterday. "We can remove some by a chemical, a chelating agent. But over time the iron buildup can lead to serious heart disease or other disorders.

"Most thalassemia patients, without treatment, die very young. By cutting their transfusions in half, we should be able to diminish the hazards very greatly, and extend the good the transfusions can do."

The new treatment was demonstrated yesterday by doctors in the blood bank and hematology (blood disease) unit of NIH's Clinic Center.

The human body constantly makes new blood cells, they explained. Each red cell lives about 120 days then is replaced.

Thus an ordinary blood transfusion is a mix of old blood cells and new. If the patient has a chronic blood disease he or she may need a transfusion every two to three weeks to have enough fresh new red cells.

What the NIH and Boston doctors have learned to do is separate new red cells, or neocytes, from old ones. They do it be centrifuging or whirling, the blood to separate the new cells, which are lighter and larger than old ones.

The slow, meticulous separation is done while the blood donor lies in a bed at the blood bank. The donor's blood leaves one arm, passes through the separation machinery then returns through the other arm -- until after four hours -- enough young red cells have been collected to make one unit or pint.

The current NIH patient is 25-year-old, Greek-descended Judy Lambis of Washington. Two months ago her brother, Nicholas, 27, died of Thalassemia. w

For one year now, she has been getting a red cell transfusion every four to six weeks.

"Right now I'm doing fine," she said at the NIH hospital. "I got a transfusion last night, and it perked me up. Next month I expect to be going home."

Thalassemia -- a disease in which there is a chronic shortage of hemoglobin, or red blood matter -- destroys many of its victims in childhood, or even in the womb. There are some 1,500 Americans who have it so seriously they could benefit from the new transfusions, NIH doctor said.

Altogether, said Propper, "10,000 to 15,000 persons in this country" could be given a better chance for life.