Abstract: Objective To study the serological changes, laboratory detection methods, and transfusion strategies for patients with positive anti-E unexpected antibodies after umbilical cord blood hematopoietic stem cell transplantation with E-positive antigens. Methods ABO and Rh blood typing and unexpected antibody screening tests were performed using conventional serological methods. Unexpected antibody identification was conducted using PEG enhancement technology and acid elution test. Cell population detection was carried out using flow cytometry to analyze the patterns of blood group antigen conversion and antibody resolution. Results The patient had pretransplant blood type AB, Rh type CCDee, with anti-E unexpected antibodies. Unrelated cord blood HSC donor was type B, Rh classification was ccDEE, related hemicompatible peripheral blood HSC donor was type AB, and Rh classification was CcDEe. The patient was in blood group transition and the unexpected antibody screening result was negative, but IgG anti-E antibody was detected by PEG enhancement test and erythrocyte acid release test. Conclusion For patients with similar antibodies before transplantation, PEG enhanced anti-human globulin test is recommended as a supplement to routine serological tests, monitor the changes of alloantibody levels, prevent hemolytic reaction and avoid red cell transfusion refractoriness.

Key words: Anti-E antibody, Unrelated Umbilical Cord Blood Hematopoietic Stem Cell Transplantation, Rh blood group transformation, Flow cytometry