Identification of Rh Alloimmunization after Rh Antigen Incompatible Red Blood Cell Transfusion

The rhesus (Rh) blood group system is one of the most important systems in transfusion medicine.Rh alloantibodies can cause hemolytic transfusion reactions and difficulties in finding compatible blood.On the other hand, the phenotypic test and pre-transfusion compatibilization for RhCE antigens have not been routinely performed in most clinical laboratories.This study examined the occurrence of Rh alloimmunization, including C, c, E, and e antigens, after Rh incompatible red cell transfusion during a specific period.From November 2016 to December 2017, clinical and laboratory information of transfused patients was collected; this included the transfusion history and Rh phenotypes of the patients and transfused red blood cell (RBC) products.Of 3,623 patients who received red cell transfusion, 99 (2.8%) revealed unexpected antibodies.Among them, 48 patients (48.5%) had alloantibodies to the Rh-system antigen, including the anti-D antibody.Based on the transfusion history and Rh phenotypes of patients and transfused packed RBCs, 11 patients (11.1%) were assumed to develop Rh alloantibodies after discrepant Rh phenotype red cell transfusion.A considerable proportion of unexpected antibodies was caused by the exposure of Rh mismatched red cells.Therefore, extended Rh antigen matching, including the C, c, E, and e, is needed to prevent alloimmunization.(