ABO Incompatibility

Transfusion Safety
ABO-Rh Compatibility
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ABO-Rh Compatibility

The presence or absence of A and/or B antigens and antibodies, as outlined in the graph below, is the basis for determining ABO type compatibility between patient and donor. ABO antibodies develop naturally starting at approximately 3 months of age, whereas antibodies against Rh occur in Rh negative individuals only after exposure to Rh positive blood. When assessing the compatibility of blood and components, both patient and donor antigens and antibodies must be considered.
ABO Antigens/Antibodies

Blood Type Antigens on
Red Cells
Antibodies in
O Neither A nor B Anti A and Anti B
A A Anti B
B B Anti A
AB A and B Neither Anti A nor Anti B