Trial to Reduce Alloimmunization to Platelets (TRAP)

Objectives

To conduct a multi-institutional, randomized, blinded trial to determine whether the use of platelets from which leukocytes had been removed by a filter or that had been treated with ultraviolet B irradiation would prevent the formation of antiplatelet alloantibodies and refractoriness to platelet transfusions.

Background

A 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.

Subjects

1047 male and female thrombocytopenic patients, ages 15 and over, newly diagnosed with acute myelogenous leukemia (AML) and undergoing chemotherapy were screened with 603 of them being enrolled between January 14, 1991, and February 28, 1995. Patients were excluded because of no or low-dose chemotherapy, a prior hematopoietic disorder treated with transfusions, prior chemotherapy, logistic reasons, prior treatment for leukemia, refusal to enter the study, or administration of corticosteroids.

Design

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 (F-PC), ultraviolet irradiated pooled random donor platelets (UVB-PC), or leukocyte-poor filtered single donor apheresis platelets (F-AP). Patients in the control group received routinely pooled, random-donor platelets. All patients received transfusions of filtered, leukocyte-reduced red cells. 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.

Conclusions

Reduction of leukocytes by filtration and ultraviolet B irradiation of platelets are equally effective in preventing alloantibody-mediated refractoriness to platelets during chemotherapy for acute myeloid leukemia. Platelets obtained by apheresis from single random donors provided no additional benefit as compared with pooled platelet concentrates from random donors (NEJM 1997;337:1861-1870)

Publications

Slichter SJ, Davis K, Enright H, Braine H, Gernsheimer T, Kao KJ, Kickler T, Lee E, McFarland J, McCullough J, Rodey G, Schiffer CA, Woodson R. Factors affecting posttransfusion platelet increments, platelet refractoriness, and platelet transfusion intervals in thrombocytopenic patients. Blood. 2005; 105(10):4106-14.

Enright H, Davis K, Gernsheimer T, McCullough JJ, Woodson R, Slichter SJ. Factors influencing moderate to severe reactions to PLT transfusions: experience of the TRAP multicenter clinical trial. Transfusion. 2003; 43(11):1545-52.

Davis KB, Slichter SJ, Corash L. Corrected count increment and percent platelet recovery as measures of posttransfusion platelet response: problems and a solution. Transfusion. 1999; 39(6):586-92.

Leukocyte reduction and ultraviolet B irradiation of platelets to prevent alloimmunization and refractoriness to platelet transfusions. The Trial to Reduce Alloimmunization to Platelets Study Group. N Engl J Med. 1997; 337(26):1861-9.

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