ABO is the most important group system. The Rh antigens are of pivotal importance both to transfusion medicine and to obstetrics and neonatology; the D antigen is the most immunogenic of all the common blood group antigens, and anti-D is still the most common cause of hemolytic disease of the new-born. See ABO & Rh Phenotyping and Genotyping by PCR
Abnormal plasma proteins, potent cold autoagglutinins, positive direct antiglobulin test, and (in some cases) bacteraemia may interfere with test interpretation. Do not freeze.