Antibody Screen (Indirect Antiglobulin Test) |
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The antibody screen detects alloantibodies and autoantibodies in patients' sera, which have specificity for red blood cells. Approximately 1.5-2% of patients has alloantibodies to red blood cell antigens caused by previous transfusion or pregnancy. Even though blood is ABO and Rh compatible, a recipient of a transfusion may still develop an alloantibody to one or more of the hundreds of red blood cell antigens present. Even components containing very few red blood cells, such as pooled platelet concentrates can stimulate antibody formation. Any antigens that the patient does not possess are potentially immunogenic. The most commonly detected antibodies in order of decreasing frequency are; D>K>E>CD>Fya>Jka> c>C>cE>e>DE>V>Jkb. Approximately one in 400 hospital patients have anti-D. These antibodies may cause a hemolytic transfusion reaction if they are not detected and antigen negative units of red blood cells are not given.
Autoantibodies are detected in about one in 9000 healthy adults. Autoantibodies may shorten the survival of the patient's own red blood cells. Autoimmune hemolytic anemia has an incidence of one case per 80,000 and most often occurs in people older than 60 years.
Specimen requirement is one 15 mL red top tube of blood labeled with patient's full name and hospital number.
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