Why Knowledge of A Subgroups Is Important For Laboratory Professionals

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The page below is a sample from the LabCE course Introduction to the ABO Blood Group System. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Why Knowledge of A Subgroups Is Important For Laboratory Professionals

For the most part, subgroups are merely of academic interest, but occasionally they present clinical problems. The antigen may be so weak that it is not detected, and the red cells are mistyped as group O. This is especially dangerous if the cells are those of a donor. Problems may arise because the serum of an A2, A2B, A3, or Ax individual might contain anti-A1. This antibody may be detected in serum typing and cause confusion. You would not expect to find a person with A antigen on his/her red cells and anti-A in the serum. Anti-A1 is produced by about 4% of group A2 individuals and about 25% of group A2B individuals. Subgroups may be determined by reactions with antisera, as seen in the table on the next page.