How does a direct match test check whether donor blood is compatible with a recipient?

The direct match test, also known as a crossmatch, is a critical safety procedure used to ensure that donor blood is compatible with a recipient before a transfusion occurs. Its primary purpose is to detect the presence of antibodies in the recipient’s serum that would react against the antigens carried on the donor’s red blood cells.1

The test is performed by mixing the recipient’s serum with the donor’s red blood cells. To ensure comprehensive screening, this process often incorporates the Coombs test (or antiglobulin test), which is specifically designed to detect antibodies that could trigger life-threatening immune destruction during a transfusion.12

If the test indicates that the recipient’s serum contains antibodies targeting the donor’s cells, the blood is deemed unsuitable for transfusion, as it could cause a hemolytic transfusion reaction. By identifying these incompatibilities beforehand, medical professionals uphold the ethical imperative to protect patient safety and prevent potentially fatal complications.1