A Coombs Test,  is a blood test that detects antibodies that attack Red Blood Cells.

Coombs tests are not the same as another test run in diagnosing Cold Agglutinin Disease.   Coombs is often confused with, See: Cold Agglutinin, Quant which results are a Titer or ratio

Some other related names. Direct Coombs Test, Indirect Coombs Test, Antiglobulin Test, Direct Antiglobulin Test, or DAT.

Antibodies are proteins made by the bodies own immune system, to bind to foreign substances and destroy them.  In a healthy body the antibodies are used to destroy foreign Bacteria and Viruses.  In a CAD, they are attacking the bodies own Red Cells.

The presence of these antibodies refers to a condition known as Hemolytic Anemia.   The point in which the body does not contain adequate Red Blood Cells because they are prematurely destroyed by excessive Hemolysis.

In the case of CAD, which is a form of Hemolytic Anemia, the Hemolysis is triggered due to varying influences of Cold temperatures.

Test Results are considered normal if there is no Clumping of Red Blood Cells

There are two tests that are often used.

Direct Coombs Test:  Or Direct Antiglobulin Test (DAT).  More common test, and checks for IgG antibody, and C3 Proteins, that are attached to the surface of the Red Blood Cells.

Normal Negative: No Agglutination

Positive: If Agglutination shows immediately, clumping is read on a scale up to +4.

But the test isn’t simply “positive” or “negative”.  It is used to detect Red Blood Cell binding Antibody (IgG),  or (C3 Protein), that may be present on the surface of the Red Blood Cells membrane.  If IgG or C3 is present on the Red Blood Cells, Agglutination occurs.

With CAD, you typically see a negative (or weak) IgG, and a positive C3 result on the Coombs test.

[Note] C3 is a protein in your blood.  A series of C proteins are part of your “Complement System” Which is part of your Immune system that helps kill bacteria and viruses that cause disease.

Conditions that may cause you to have antibodies attached to Red Blood Cells:
Autoimmune Hemolytic Anemia
Transfusion Reaction
Mycoplasma Bacterial Infection
Drug related Toxicity
Erythroblastosis Fetalis (infants)

Indirect Coombs Test: 
Or Indirect Antiglobulin Test (IAT)Checks for Antibodies  that are floating around in the bloodstream.  This test is also used to determine if there is the potential of a bad reaction to a Blood Transfusion.

Negative: No Agglutination
Positive: If Agglutination shows

Conditions that may cause you to have Antibodies in your Bloodstream:
Incompatible blood match during a blood transfusion
Autoimmune Hemolytic Anemia
Drug related Toxicity
Erythroblastosis Fetalis (Infants)