What Is Antiglobulin?

Christine DiMaria

Antiglobulin is an antibody that is part of a reaction to the serum protein immunoglobulin. This antibody can be found naturally, but it also can be created in lab animals to combat human globulin. In blood typing, certain antiglobulins are utilized in recognizing certain antibodies.

A blood sample must be taken before a Coombs test can be performed.
A blood sample must be taken before a Coombs test can be performed.

An antiglobulin test (AGT), or Coombs test, is a blood test that uses the antibody immunoglobulin. The antiglobulin test is used to find the cause of hemolysis or immune-mediated anemia. This test ultimately detects cells coated with antibodies or antibodies in serum. The Coombs test comes in two forms: direct and indirect.

The indirect version of an antiglobulin test is particularly useful in testing for patients prior to blood transfusions.
The indirect version of an antiglobulin test is particularly useful in testing for patients prior to blood transfusions.

The direct Coombs test is the more frequently used test. Its used to sense the presence of autoimmune hemolytic anemia. This test also can be used to find the cause of jaundice. In addition, methyldopa, procainamide and quinidine lead to production of antiglobulin, and the Coombs test can accurately detect this. This enables treatment for the anemia that might be caused by the production of antibodies.

The sample must be processed correctly before the antiglobulin can be added, or the test will not be accurate.
The sample must be processed correctly before the antiglobulin can be added, or the test will not be accurate.

Some conditions result in an individual’s blood containing immunoglobulin G (IgG). These antibodies attach themselves to antigens on red blood cells. The complementary proteins or antiglobulins bind to the antibodies or globulins.

A variety of diseases can be detected based on the outcome of the Coombs test.
A variety of diseases can be detected based on the outcome of the Coombs test.

During the Coombs test, a phlebotomist or other medical professional takes a blood sample. The red blood cells are washed to rid the sample of the patient's plasma, and antiglobulin is then applied to the sample. This antiglobuin is also referred to as the Coombs reagent. If the red blood cells clump, then the test is positive. If there is not any agglutination of the red blood cells, then the test is negative.

The Coombs blood test is sometimes administered as part of prenatal testing.
The Coombs blood test is sometimes administered as part of prenatal testing.

The indirect version of the Coombs test is particularly useful in testing for patients prior to blood transfusions. This blood test is used for prenatal testing, as well. The indirect antiglobulin test identifies antibodies against red blood cells that are within the patient’s blood serum. This is conducted by extracting the serum and infusing it with red blood cells of known antigens. The test results are determined by the result of the clotting.

A variety of diseases can be detected based on the outcome of the test. Overall, antiglobulin plays an important role in the field of immunology and immunohematology. Individuals who have autoimmune disorders rely on antiglobulim to identify the antibodies that are the culprit of destroyed tissue. Certain types of cancer, such as lymphoma and Hodgkin's disease, also can be identified by Coombs testing. Testing with the antigen for globulin is even beneficial for identifying systemic lupus erythematosus, mononucleosis, syphilis and hemolytic disease in newborns.

Antiglobulin can be used in several types of blood tests.
Antiglobulin can be used in several types of blood tests.

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