Blood typing

Blood typing is laboratory testing that identifies blood-group antigens on red blood cells and antibodies in plasma to assess compatibility for transfusion.

ABO blood group system: A blood-group system defined by A and B antigens on red blood cells and corresponding antibodies in plasma. ABO typing identifies the system whose mismatches can cause rapid, severe transfusion reactions.
Blood transfusion: The transfer of blood or blood components into a person's circulation. Blood typing helps select compatible red-cell units for transfusion.
Antigen: A molecular structure that can be specifically recognized by an antibody or immune receptor. Blood-group antigens are the red-cell features identified during typing.
Universal donor: An informal designation for a donor whose red cells are compatible with many recipients under specified conditions. The label does not replace full typing, antibody screening, or compatibility testing.
Rh blood group system: A blood-group system whose most clinically significant antigen is the D antigen. RhD typing identifies another major source of transfusion incompatibility.
Hemolytic transfusion reaction: The destruction of transfused red blood cells by an immune response in the recipient. Incompatible antigens can trigger this potentially severe complication.
Antibody: A protein made by B cells that binds a specific molecular target. Typing and antibody screening assess antibodies that may react with donor red cells.
Universal recipient: An informal designation for a recipient whose ABO and RhD type permits receiving many red-cell types. This shorthand does not account for other blood-group antigens or unexpected antibodies.
Forward typing: A test that detects A and B antigens on a person's red blood cells using known antibodies. It establishes the red-cell antigen pattern in ABO typing.
Hemolytic disease of the fetus and newborn: Fetal or newborn red-cell destruction caused by maternal antibodies crossing the placenta. Maternal blood-group antibody testing helps assess this pregnancy risk.

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