Cross-matchinging is performed to determine if donor blood cells will be compatible with an intended recipient. It usually takes about 1 hour to perform. This is not the same as a type and screen which is a process used to determine a patients ABO-RH blood type AND screen for the common antibodies in the patients serum. Cross-matching will identify incompatibilities that will not be evident on Type and Screen alone; however, cross-matching will not pick up on low titer antibodies and therefore will not prevent delayed-type hemolytic transfusion reactions.
There are two types:
Major Cross-match (donor cells/recipient serum): donor packed cells are combined with recipient serum to determine if the RECIPIENT has pre-formed antibodies against any of the donor cells. This is the mandatory cross match that has to be done before a blood bank will release blood to a patient.
Minor Cross-match (donor serum/recipient cells): recipient red cells are combined with donor serum to detect donor antibodies against recipient cell antigens. This is not a required crossmatch.