This test is designed to identify red cell antibodies that are present in the blood. A person may develop antibodies that react with antigens on red blood cells if they are exposed to ‘foreign’ red blood cells (e.g. through blood transfusion or during pregnancy). The red blood cell antibody identification test allows the laboratory to determine exactly which antibodies are present in the blood of a patient and this information can…This test is designed to identify red cell antibodies that are present in the blood. A person may develop antibodies that react with antigens on red blood cells if they are exposed to ‘foreign’ red blood cells (e.g. through blood transfusion or during pregnancy). The red blood cell antibody identification test allows the laboratory to determine exactly which antibodies are present in the blood of a patient and this information can then be used to ensure that if they require blood or blood products, only those from a suitable donor (i.e. someone who does not have antigens on their cells that would react with the patient’s antibodies) are used. Red cells carry many different proteins and substances on their cell membrane surface that can act as antigens. An antigen is any substance that may be recognised by the immune system and stimulate an immune response that generates antibodies. The combination of antigens present on the surface of red blood cells determines your blood type. The major red cell antigens include the A, B and Rhesus (Rh) antigens that determine a person’s basic blood types (for more on this, see Blood Type and Blood Banking). The ABO blood group system is the most important blood group system in blood transfusion because our bodies naturally produce antibodies against A and B antigens, depending on whether or not they are present on our own red blood cells. A person who is blood group A will have A antigens on their own red cells and produces anti-B antibodies; a person with blood group B has B antigens on their red cells and produces anti-A antigens; a person of blood group O does not express A or B antigens on their own red cells and produces both anti-A and anti-B antibodies; a person with blood group AB has both A and B antigens on the surface of their red blood cells and does not produce antibodies to either of these. These naturally occurring antibodies are present in almost all by the age of 6 months and are very potent; if a person of blood group O was exposed to blood group A or B red cells, their antibodies would rapidly attack and destroy the foreign red cells. This destruction of red cells is called haemolysis.Blood group Naturally occurring RBC antibodies that can be found in the blood O Anti-A and anti-B A Anti-B B Anti-A AB None The second most important blood group system in blood transfusion is the Rhesus blood group system. If the Rhesus D antigen is present then this makes an individual Rh D positive; this is combined with the ABO blood group to describe an individuals’ basic blood group, e.g. A+, B-, O+, etc. The Rh D antigen is very important because, although antibodies against Rh D do not occur naturally in individuals who are Rh D negative, if these individuals are exposed to even a small amount of Rh D antigen there is a potent immune response with production of anti-D antibodies which are also capable of destroying red cells and causing haemolysis. It is estimated that a Rh D negative person needs to be exposed to only one or two drops of Rh D positive blood to trigger the production of anti-D antibodies. The pattern of red cell antigens and therefore the blood group of an individual will be determined by their genetic make-up and so blood groups are inherited traits. The major blood group systems (ABO and Rhesus) represent only two of the 33 currently recognised blood group systems. These other blood group systems include the Kell, Duffy, Kidd and Lutheran groups to name a few. These other blood group systems are not associated with naturally occurring antibodies; as for the Rh system a person must be exposed to red cells carrying the foreign antigen before they mount an immune response producing antibodies. A person will not usually develop antibodies against the blood group antigens present on their own cells but may develop antibodies against other blood group antigens that they are exposed to, e.g. if they receive blood from another individual during a blood transfusion. This is the reason why a ‘group and screen’ procedure is performed to identify the blood group and screen for the presence of any antibodies in blood during the blood transfusion screening process. If antibodies to red cells are identified during this process the red cell antibody identification test is performed to identify exactly which antibodies are present and allow for screening of donor blood and selection of only matched units (i.e. antigen negative donor red cells) for cross-matching. The presence of red cell antibodies may also be detected by a positive direct antiglobulin test (DAT). It is very important to identify the presence of red cell antibodies. If a person with red cell antibodies is exposed to red cells which carry the antigenic target then antibodies will attach to the red cell antigen on the surface of the cells, coating the red cell and targeting it for destruction (haemolysis). Depending on the specific antibody-antigen reaction and the quantity of red cells that are affected, this can cause a reaction ranging from mild to severe and potentially life-threatening. Depending on the antigen and antibody involved and the quantity of RBCs affected, this can cause a reaction ranging from mild to severe and potentially life-threatening. It may happen immediately, such as during a blood transfusion, or take longer, from one to several days following a transfusion. When antibodies attach to antigens, the red blood cells can be destroyed, termed haemolysis. This can occur within the blood vessels or in the liver or spleen and cause symptoms and signs such as fever, chills, nausea, flank pain, low blood pressure, bloody urine, and jaundice. Specific antibody identification tests that characterise antibodies directed against the minor red cell blood group antigens are not routinely done on every patient, but these are performed when the presence of an antibody is detected through a positive IAT using a mixed panel of cells carrying all clinically significant antigens, or when antibodies are detected by a positive DAT. How is the sample collected for testing? A blood sample is obtained by inserting a needle into a vein in the arm. Is any test preparation needed to ensure the quality of the sample? No test preparation is needed. See MoreSee Less
