Direct antiglobulin

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Also known as: Direct Coomb’s test; Coomb’s test; DAT; DCT; DC
Formal name: Direct antiglobulin test

At a Glance

Why Get Tested?

To screen and monitor diseases or conditions that result in destruction of red blood cells such as haemolytic anaemia, transfusion reactions and haemolytic disease of the newborn (HDN).

When to Get Tested?

If your doctor suspects that your immune system may be destroying your red blood cells. This may be indicated by anaemia (low haemoglobin or red cell count), small red blood cells (microcytic anaemia) and other signs of red blood cell destruction.

In newborn babies this can occur due to antibodies from the mother attacking the baby’s red blood cells either before, or immediately after, birth.

Sample Required?

The direct antiglobulin test is performed on a blood sample taken by a needle placed in a vein in the arm or by a finger-prick (for children and adults) or heel-prick (for infants).

Test Preparation Needed?

None

The Test Sample

What is being tested?

Red blood cells have chemical structures (most commonly proteins or carbohydrates) on the outside surface. These chemical structures usually have a defined function such as determining the shape of the cell or the transport of chemicals into, or out of, the red blood cell. In addition, they determine our blood group. There are over 200 different blood groups known.

Our immune system is very good at recognising foreign particles that may be harmful to us. Occasionally however this gets mixed up and our immune system recognises parts of our own body as being foreign, and then tries to destroy them. This group of diseases are known as autoimmune diseases, and include a range of conditions including some forms of arthritis.

Some autoimmune diseases attack and destroy red blood cells. This results in anaemia and in some cases may be life threatening. A similar situation occurs in some types of transfusion reactions. In pregnancy, red blood cell antibodies can cross the placenta and enter the baby’s bloodstream. These can destroy the baby’s red blood cells resulting in anaemia. As they break down they release bilirubin, resulting in jaundice. This needs to be treated promptly to prevent complications, and even death, of the baby.

This test tells the doctor whether red blood cell antibodies are attached to the red blood cells and, if they are, what type of antibody it is. This can be used to assist and monitor treatment.

How is the sample collected for testing?

The direct antiglobulin test is performed on a blood sample taken by a needle placed in a vein in the arm or by a finger-prick (for children and adults) or heel-prick (for infants).

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.