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:
- When blood bankers use the term “crossmatch” in pretransfusion testing, they really mean “major crossmatch” in virtually all situations
- 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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