Red Blood Cell Antibody Identification : labtest

Why Get Tested?
To identify the specific antibody present when a direct antiglobulin test (DAT) or indirect antiglobulin test (IAT) is positive; to help identify the cause of a transfusion reaction or the cause of hemolytic disease of the newborn (HDN)
When to Get Tested?
When an IAT screening test is positive when performed as part of a prenatal workup or prior to a blood transfusion; when a person has a positive DAT following a suspected transfusion reaction or is suspected to have an autoimmune hemolytic anemia; when a newborn has HDN
Sample Required?
A blood sample drawn from a vein in your arm

How is it used?
Antibody identification is used as a follow-up test to a positive indirect antiglobulin test (IAT). The IAT is typically performed during each pregnancy to determine whether the mother has developed any red blood cell (RBC) antibodies and before RBC transfusions as part of a "type and screen" or "type and crossmatch." The antibody identification test is used to determine the RBC antigen(s) that the antibody or antibodies are directed against to determine if they are likely to be clinically significant, i.e., if they are likely to cause a transfusion reaction or hemolytic disease of the newborn (HDN). Some RBC antibodies are known to cause moderate to severe reactions while other less significant ones may cause a positive IAT but few to no symptoms or complications in the blood transfusion recipient or baby.
If one or more clinically significant RBC antibodies are identified, then donor blood that lacks the corresponding RBC antigens must be used for transfusion. When someone has a condition that requires recurrent transfusions, they are exposed to many foreign RBC antigens and may develop multiple RBC antibodies over time, making the process of finding compatible blood increasingly challenging.

An IAT and antibody identification test may be used as part of an investigation if a person has a transfusion reaction. Sometimes an RBC antibody may be present in such a small quantity that it does not cause a positive IAT during pre-transfusion blood compatibility testing. But after the blood is given to the recipient, it can trigger renewed, rapid antibody production and cause a delayed hemolytic transfusion reaction several days later.

If RBC antibodies have been identified in a pregnant woman, then the baby's condition will be monitored. Whether or not the antibodies will affect the baby's condition depends upon the antibody present, the RBC antigens that the fetus has, and when the mother's antibodies come into contact with the fetus's blood. Some antibodies can cross the placenta from mother to baby and cause HDN.

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