Major Crossmatch

A “major” crossmatch is used to assess the compatibility of a donor’s red blood cells with the recipient’s plasma. For example, if a donor is blood group A and a recipient is blood group B, blood bank personnel performing a major crossmatch prior to transfusion would mix the recipient’s plasma/serum (containing anti-A antibodies) with the donor’s group B red blood cells. Obviously, in this example, you would expect the result to be incompatible, and the blood would not be given (OK, don’t send me e-mails about that scenario. That is obviously a make-believe case, and you wouldn’t deliberately select group B red cells for a group A recipient!).

TWO IMPORTANT NOTES:

1. When blood bankers use the term “crossmatch” in pretransfusion testing, they really mean “major crossmatch” in virtually all situations
2. The main function of the major crossmatch is to serve as the final check of ABO compatibility between donor and recipient before transfusion

Obviously, if there is a “major” crossmatch, there must also be a “minor” crossmatch, and there is (though we really don’t use it). Multiple types of major crossmatches exist, including immediate spin, computer (electronic), and AHG (“full”) versions.

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