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.