Transfusion-Related Alloimmunization to Red Blood Cell Antigens in Japanese Pediatric Recipients.

Red blood cell (RBC) transfusion to neonates is thought to rarely provoke an immune response. Neonatal testing guidelines suggest that antibody screening is not necessary when the mother has no antibodies. Alternatively, maternal blood samples can be used for antibody screening and cross-matching. However, the guidelines are based on small-scale studies of white-dominant populations. Furthermore, transfusion-related alloimmunization is less well established among children and adolescents as a whole among Japanese and East Asians. To elucidate the incidence of transfusion-related alloimmunization among neonates, children, and adolescents, and whether current guidelines are applicable to Japanese populations, a nationwide retrospective multicenter cohort survey was conducted in 50 tertiary-care hospitals in Japan. Between 2001 and 2015 inclusive, recipients of at least 1 allogeneic RBC transfusion were categorized into groups A-F according to their age at the time of transfusion: (A) neonates <1 month; (B) infants 1 to <12 months; (C) children 1 to <5 years; (D) prepubescents 5 to <10 years; (E) young pubescents 10 to <15 years; and (F) adolescents/young adults 15 to <20 years. Excluding maternally derived antibodies and naturally occurring, cold-reactive, and/or nonspecific antibodies, 69 (0.61%) of 11350 RBC recipients <20 years old formed at least 1 clinically significant alloantibody. The alloimmunization rate differed significantly (P < .0001) by age: none (0%) of 3407 in group A; 11 (0.46%) of 2410 in group B; 18 (0.76%) of 2361 in group C; 9 (0.80%) of 1119 in group D; 12 (1.15%) of 1043 in group E; and 19 (1.88%) of 1010 in group F. Clearly different incidences of alloimmunization emerged in group A compared to B, C, D, E, or F, as confirmed by logistic regression analysis adjusted by numbers of donor exposure. Alloimmunization did not occur from RBC transfusions within the first month of life and rarely occurred (0.46%-0.80%) after transfusion within the first decade of life. Alloimmunization occurred in 1.15%-1.88% of young pubescents and adolescents/young adults. These findings support the use of guidelines developed in Europe and the United States for East Asian pediatric recipients.