Blood compatibility testing is performed before
blood transfusion, including matching of the
ABO blood group system and the
Rh blood group system, as well as screening for recipient antibodies against other human blood group systems. Blood compatibility testing is also routinely performed on pregnant women and on the
cord blood from newborn babies, because incompatibility puts the baby at risk for developing
hemolytic disease of the newborn. It is also used before
hematopoietic stem cell transplantation, as it may be responsible for some cases of acute
graft-versus-host disease. Other human blood group systems than ABO and Rh have a relatively small risk of complications when blood is mixed. Therefore, in emergencies such as major
hemorrhage, the urgency of transfusion can exceed the need for compatibility testing against other blood group systems (and potentially Rh as well). When needing to give red blood cell transfusion to a patient, the presence of clinically significant antibodies produced by the patient can be detected by mixing patient serum with 2 to 4 "screening" or "control" red blood cells that together display essentially all relevant antigens. If any of these mixes display a reaction (evidence of patient antibodies binding to the screening red blood cells), a more extensive antibody panel is warranted (as imaged at right). == See also ==