ABO Rh Typing

The ABO system is the most clinically significant blood group system in transfusion medicine.

• Carbohydrate antigens
• Non-RBC stimulated: individuals possess ABO antibodies to the antigens that they lack
• IgM
• Cause severe transfusion reactions
  • Cell lysis and hemolysis

ABO Genes

• A and B genes present on chromosome 9
• A and B co-dominant, O is recessive
• One allele received from each parent

ABO Typing

• Babies: perform forward testing ONLY
• Babies: if baby appears Rh Negative and the mother is Rh Negative, perform weak D testing
• AB Rh Positive patients require Rh Control to be performed
  • RHC should be a reaction of 0. This checks that the agglutination seen is not a result of autoagglutination in the patient.
• Rh Control is also used for discrepancies (Rh testing results don't match, e.g. Anti-D1 is 2+ and Anti-D2 is 0)
• Rh Control is also used for IAT Testing (e.g., Weak D testing)