Trial to Reduce Alloimmunization to Platelets (TRAP)

BACKGROUND:

Between 1971 and 1980, there was a 598 percent increase in the use of platelet concentrates from 0.41 million to more than 2.86 million annually. In contrast, red cell transfusions in the United States rose concurrently from 6.3 million annually to 9.9 million, an increase of 58 percent. Although red cell transfusions have leveled or even decreased slightly in the past several years, the use of platelets has continued to increase at a rate of at least 5 to 10 percent each year. This dramatic and continued increase in the use of platelet concentrates is largely the result of treating thrombocytopenic cancer patients. In addition, open heart surgery patients and others given massive transfusions also receive substantial platelet support. Nevertheless, it is the chronically transfused thrombocytopenic patient who frequently develops platelet alloimmunization and accounts for a large percentage of the increased demand for platelets. A recent survey in a large transfusion service indicated that 8 percent of the patients had received 35 percent of the random-donor pooled platelet concentrates. Although some alloimmunized patients can be supported by HLA-matched, apheresis-donor platelets, suitably matched donors are not available in sufficient numbers for every patient. Thus, platelet transfusion programs that could prevent, or at least delay platelet alloimmunization would be of substantial benefit.

Limited studies have suggested several approaches that may reduce or prevent platelet alloimmunization: reducing the number of foreign antigens to which a recipient is exposed by providing single donor platelet apheresis products; providing leukocyte-poor blood products; inactivating donor antigen presenting cells (APC's), a type of lymphocyte contained within the transfused platelet products, by ultraviolet (UV) irradiation of platelet concentrates.

The initiative was recommended by the Blood Diseases and Resources Advisory Committee in May 1987 and approved by the National Heart, Lung, and Blood Advisory Council in September 1987. The Requests for Applications were released in June 1988.

DESIGN NARRATIVE: