Trial Information

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.