Cross-matching will identify incompatibilities between the donor and receiver that blood type would not reveal (as blood typing is not available against every blood group, just the major ones). Also, the cross-match process will not detect low titer antibodies, preventing delayed-type hemolytic transfusion complications. The main cross-match, which compares donor erythrocytes to recipient serum antibodies against donor erythrocytes, is the most critical cross-match. The minor cross-match compares donor serum to recipient erythrocytes and looks for preexisting antibodies in donor serum that might hemolyze receiver red blood cells.
When there is a severe incompatible reaction on the main cross-match, the donor blood should never be transfused. The transfusion can proceed if there is an incompatible response on the minor cross-match. If the donated serum is anticipated to contribute significantly to the recipient's plasma volume, the serum should be separated from the donor whole blood. Before infusion, the packed cells (washed or unwashed) should be reconstituted in sterile isotonic saline. It should be noted that if adult horses get cross-match-incompatible blood on the first transfusion, the transfused red blood cells will have significantly reduced survival and minor non-hemolytic responses may occur.
Cross-matching. (n.d.). EClinpath. Retrieved February 24, 2023, from https://eclinpath.com/hemostasis/transfusion-medicine/blood-type-incompatibility-testing/#:~:text=When%20there%20is%20an%20incompatible