Ultraviolet light-based pathogen inactivation and alloimmunization after platelet transfusion: results from a randomized trial.

Background: The current study explored whether pathogen-reduction treatment of platelet components before transfusion would decrease the risk of alloimmunization.

Study Design And Methods: Study participants were patients with hematologic cancer who were included in two parallel, randomized clinical trials testing pathogen-reduction treatment versus conventional platelets using the Mirasol or Intercept pathogen-reduction systems. Patients who had a baseline, pretransfusion sample and a follow-up, posttransfusion sample were included in the study (n = 179 patients in each study arm). Human leukocyte antigen antibody levels were determined using a commercial multianalyte, bead-based assay.

Results: The rate of human leukocyte antigen Class I alloimmunization at the clinical sites in recipients of conventional platelets was low at the highest assay cutoff (range, 1.2%-5.9%). Consistent with prior studies, human leukocyte antigen antibodies were first detected from 3 to 35 days after transfusion. There were no statistically significant differences between alloimmunization rates in patients who received pathogen-reduction treatment versus conventional platelet transfusions. Although he difference was not statistically significant, the effect size for protection from alloimmunization was greatest for high-level human leukocyte antigen Class I antibodies (approximately threefold) in the Intercept-treated patients compared with those who received conventional platelets. In the Mirasol study, only two patients and one patient in the control group developed medium-level or high-level antibodies, respectively, so it was impossible to determine an effect size for potential protection.

Conclusions: The current study was not sufficiently powered to determine whether pathogen-reduction treatment provides protection from human leukocyte antigen alloimmunization in platelet transfusion recipients. The data presented will be useful in the design of future trials and endpoints powered to detect a protective effect.