Diagnosis: Blood group systems vs collection
• A blood group system consists of one or more antigens controlled at a single gene locus, or by two or more very closely linked homologous genes with little or no observable recombination between them.
• There are currently 31 blood group antigen systems.
• Some antigens are low-prevalence antigens with a very low frequency in the population. Although these antigens may not be detected on antibody panels (because they are so rare that they are not present on most antibody panels), potential transfusion reactions can be avoided by perfoming a full crossmatch before release of the blood product.
• Band 3 is a red cell anion exchanger and is important for attachment of the red cell membrane to the cytoskeleton.
• Because acetylcholinesterase is a GPI-linked protein, expression of the Cartwright antigens is absent or decreased on red cells from patients with paroxysmal cold hemoglobinuria (PCH).
