The presence of antibodies can limit the number of compatible units available. When an antibody is identified, it is necessary to confirm that the patient's cells and the donor unit cells lack the corresponding antigens. Full crossmatch is performed following identification of clinically significant antibodies.
Limitations: Antibody may be too weak to be detected and/or identified. Antibodies to low incidence antigens may not be detected. Presence of auto-antibodies significantly complicates identification of alloantibodies and may in some cases mask their presence.