Antibody Identification

ABO antibodies are naturally occurring antibodies that are expected to be present in all individuals older than 4-6 months of age, who do not have the corresponding A and/or B antigens on their RBCs. All other antibodies to red blood cell antigens are called unexpected antibodies. Unexpected RBC antibodies may be alloantibodies or autoantibodies. Depending on the patient population, 1%-35% of patients may have unexpected alloantibodies. Once an alloantibody is detected in pretransfusion testing on the antibody screen, the antibody specificity must be determined. Some unexpected RBC alloantibodies may be clinically significant with the potential to cause shortened survival of transfused RBCs, acute or delayed hemolytic transfusion reactions, and hemolytic disease of the fetus or newborn. Patients with clinically significant alloantibodies should receive RBCs that are negative for the corresponding antigen.