Clinical Significance

The ABO system is the most clinically significant blood group system for transfusion practice. It is the only blood group system in which antibodies are consistently and predictably present in the serum of normal individuals whose red cells lack the antigen. ABO compatability between donor and recipient is the foundation upon which all other pretransfusion testing rests.

The D (Rh_o) antigen is, after A and B, the most important red cell antigen in transfusion practice due to its potent antigenicity. Unlike the ABO system, however, individuals who lack the D antigen do NOT consistently and predictably have anti-D in their serum.

The ABO and Rh is determined for all patients who are candidates for transfusion, for all blood donors, for all prenatal patients, and for all potential organ recipients and donors.

_{Source: Fung, Mark K, editor. Technical Manual, 18^th edition. Bethesda, Maryland. American Association of Blood Banks, 2014}