Coombs Test

Coombs Test Types, Purpose, Procedure, Results and more

The Coombs test checks your blood for antibodies that attack red blood cells. This test can be used to check your blood before a procedure, such as a blood transfusion. Or it can be used to find out if you have certain conditions, such as autoimmune hemolytic anemia.

Also Known asCoombs Test, Antiglobulin Test, Anti Human Globulin Test
Test PurposeThis Test to done find certain antibodies that cause autoimmune haemolysis of red blood cells (erythrocytes).
Test PreparationsNo Need any Preparations
Test ComponentsCoombs Test Direct
Coombs Test Indirect
SpecimenDirect coombs: 3 ML (2 ML Min.) Whole Blood From 1 Lavender Top (EDTA) Tube. 
Indirect Coombs: 2 ML (1 ML Min.) Serum From 1 SST. 
Stability RoomDirect Coombs: 2 hours
Indirect Coombs : 2 hours
Stability RefrigeratedDirect Coombs: 1 week
Indirect Coombs : 48 hours
Stability FrozenDirect Coombs: 2 weeks
Indirect Coombs : N/A
MethodErythrocyte Magnetised Technology
Download Report Download Report
Coombs Test
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Types of Coombs Test:

There are two different types of Coombs tests

  1. Direct Coombs Test:
    The direct Coombs test (sometimes called the direct antiglobulin test) examines red blood cells to see if they have antibodies attached to them. It is often used to diagnose blood-related conditions, such as autoimmune hemolytic anemia. People with autoimmune hemolytic anemia don’t have enough red blood cells because their bodies destroy them too soon.
  2. Indirect Coombs Test:
    The indirect Coombs test tells your provider if there are antibodies present in your bloodstream that could attach to red blood cells. It is used as a screening process to see how you will react to a blood transfusion. An indirect Coombs test is also routinely done as part of prenatal testing.

Principle of Coombs’ Test

Red blood cells coated with complement or IgG antibodies do not directly agglutinate when centrifuged. These cells are said to be IgG or complement sensitized. For agglutination to occur, an additional antibody must be added to the system that reacts with the Fc portion of the IgG antibody, or with the C3b or C3d component of complement. This will form a “bridge” between the antibodies or complement that coats the red blood cells, causing agglutination.

Coombs Test Result Mean

ResultDirect Coombs TestIndirect Coombs Test
Negative resultAntibodies not attached to Red Blood CellsAntibodies not loose in Serum
Positive resultAntibodies attached to Red Blood CellsAntibodies loose in Serum

A Positive Coombs test is seen in

A positive (abnormal) Coombs’ test means you have antibodies that can attack your red blood cells. This can be caused by various conditions, including:

  • Autoimmune hemolytic anemia.
  • Infectious mononucleosis.
  • Chronic lymphocytic leukemia.
  • Syphilis.
  • Mycoplasma infection, a type of respiratory disease.
  • Lupus.
  • A negative reaction to a blood transfusion.

Positive test during Pregnancy mean

If you test positive during your pregnancy, it means you need to take steps to protect your baby from Rh sensitization.

Positive Coombs in Baby

Generally, a positive Coombs test result in babies indicates Anemia or Jaundice.

Meaning of Negative Coombs Test Result

A negative (normal) test result is good news. It means that no antibodies against red blood cells were found.

  • You can safely receive donor blood during a transfusion.
  • You don’t have to worry about Rh sensitization affecting your unborn baby.
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