Phenotyping autologous red cells within 1 day after allogeneic blood transfusion by using immunomagnetic isolation of reticulocytes

Background: When a transfused patient develops multiple or weak blood group antibodies, posttransfusion phenotyping is useful in antibody identification. To perform a correct phenotyping after transfusion, isolation of autologous red cells is necessary. However, mature autologous red cells are impossible to separate from their donor counterparts. Since the proportion of autologous reticulocytes compared to donor reticulocytes increases rapidly after transfusion, selective isolation of reticulocytes provides autologous cells for antigen typing.Study Design and Methods: Extensive phenotyping was performed on red cells from 10 surgical patients before transfusion and on red cells and reticulocytes after the transfusion of 5 or more red cell units. Reticulocytes were isolated by using an antibody against the human transferrin receptor coupled to magnetic beads.Results: The data showed nearly full agreement between pretransfusion phenotyping of red cells and posttransfusion typing of reticulocytes. Correct phenotyping of transferred patients could be obtained 8 to 10 hours after transfusion using isolated reticulocytes.Conclusion: This method is helpful in selecting compatible blood when patients have developed antibodies and have an urgent need for further transfusions.