Trial to Reduce Alloimmunization to Platelets (TRAP)
Condition: Blood Platelets; Hematologic Diseases; Immunization; Leukemia, Myelocytic, Acute; Blood Transfusion
MeSH terms: Leukemia, Myeloid; Leukemia, Myeloid, Acute; Hematologic Diseases
Study type: Interventional
Phase: Phase 3

Summary: 
      To determine the best, clinically useful procedure to prevent or minimize platelet
      alloimmunization as a cause of refractoriness to platelet transfusion in patients undergoing
      marrow ablative chemotherapy for acute myelogenous leukemia.
    

Detailed description: 
      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:

      Randomized, double-blind. There were three treatment arms and one control arm. Patients in
      the treatment arms received either leukocyte-poor filtered pooled random donor platelets, or
      ultraviolet irradiated pooled random donor platelets, or leukocyte-poor filtered single donor
      apheresis platelets. Patients in the control group received routinely pooled, random-donor
      platelets. Patients remained on their assigned treatments for all transfusions through eight
      weeks. Assigned transfusions were discontinued only in the event of severe adverse reaction
      to the platelet transfusions, granulocyte transfusions, bone marrow transplant, withdrawal of
      informed consent, or death. Pre- and post transfusion counts were obtained for all platelet
      transfusions. Each patient was followed for one year. Recruitment continued through March
      1995. Data analysis ended in July 1997.

      The study completion date listed in this record was obtained from the "Completed Date"
      entered in the Protocol Registration and Results System.
    

Intervention name(s): platelet transfusion
Intervention type(s): Procedure
Allocation: Randomized
Masking: Double
Primary purpose: Prevention