What is an antibody screening test?

Updated: Jun 24, 2019
  • Author: Ashok Tholpady, MD, MSc; Chief Editor: Jun Teruya, MD, DSc, FCAP  more...
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Answer

Answer

Red blood cells (RBCs) carry numerous protein and carbohydrate antigens on their surface. There are over 600 antigens, which are separated into 30 blood group systems. The presence or absence of these antigens in an individual is important, because they determine the type of blood that should be given in case a blood transfusion is necessary. If a person is exposed to blood with different antigens than his or her own, he or she may form antibodies that can result in extravascular and/or intravascular hemolysis when the recipient is reintroduced to the same antigens in a future transfusion.

Naturally occurring anti-A and anti-B are the only RBC antibodies in normal human serum or plasma. All others are unexpected and can be divided into alloantibodies (an antibody to an antigen that an individual lacks) and autoantibodies (an antibody to an antigen a person has).

The antibody screening test performed in a clinical laboratory and/or blood bank is designed to detect the presence of unexpected antibodies, especially alloantibodies in the serum to antigens of the non-ABO blood group system: Duffy, Kell, Kidd, MNS, P, and certain Rh types that are considered clinically significant. These antibodies can be either immunoglobulin (Ig) M or IgG. IgM antibodies are generally considered to be less significant than IgG, because they are reactive at room temperature but not body temperature and, therefore, rarely cause hemolysis in vivo.

The antibody screening test, as part of pretransfusion compatibility testing (see Special Considerations), along with the type and crossmatch, prevents transfusion reactions such as hemolysis from occurring.


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