Coombs Test

Coombs Test

Coombs Test, The antibodies present in the serum react with such RBCs. With which (IgA) antibodies stick. Such RBC is called Sensitized RBC. Although IGA antibodies stick to their specific (Ag) antigen on the cell. But since their size is small and they are not able to agglutinate from one cell to another, the antibodies in the serum can agglutinate the RBC by covering this distance. It would also be of interest to know how AHS is achieved. Human globulin (IgA) is injected into rabbits. After a few weeks, the rabbit’s immune system produces its own antibodies against these antibodies. . In this way, blood is collected after killing the rabbit, and antibodies against human globulin (IgA) are added to the serum, thus it is called serum. Thus it contains serum antibody (AHG) or anti-hemoglobin. And it is called Coombs serum. The serum either contains antibodies specifically against IgG. Or there may be antibodies against complement.

Direct Coombs Test:

RBCs in the human body that have IgG attached to them, or that also have complement present in the coombs serum (AHG) antibodies bridge the gap between the PBCs and stick them together in the form of clumps, i.e. Helps in agglutination. In this way, you can see the agglutination of RBC with your own eyes without the help of a microscope.

Coombs Test

Test procedure:

  1. Take the patient’s blood mixed with EDTA and do three saline washes. Make a 2.5% saline suspension of RBC.
  2. Pour two drops of this saline suspension into a test tube.
  3. . And mix two drops of Coombs serum or AHG serum in the tube and centrifuge for fifteen to twenty seconds.
  4. Remove the tube. Shake the RBC with a light stroke of the finger. Look for agglutination with the help of the eye or, if necessary, with the help of a microscope.
  5. Agglutination Check Coombs test will be positive. If agglutination is not seen, the test will be negative.

If the result is negative, test the quality of AHG serum with the help of control RBC. A positive result would mean that the patient has RBC antibodies to IgG.

This test is done in various blood diseases.

  • Autoimmune hemolytic anemia
  • Erythroblastosis Fetalis
  • Hemolytic transfusions rockets

In-Direct Coombs Test:

This test is done to detect the presence of antibodies that are not attached to RBCs. But they are present in serum. For this purpose, its specific antigen is mixed with the antibodies present in the serum. If the antibodies are present in the serum, they will stick to the antibodies and appear in the form of agglutination. If antibodies are not present, agglutination will not appear even if antigen is added.

Coombs Test

Another test has to be done for this process.

In the first step, the serum is likely to contain antibodies. And O blood group RBC is mixed and incubated. So that if antibodies are present, they stick to the RBC. In the second step, RBCs are tested to see if the antibodies have adhered.


  • Make a 2.5% suspension of blood group O RBCs
  • Add one drop of the suspension to the tube
  • And mix two drops of the patient’s serum in this test tube and mix well
  • Add two drops of 22% Buin’s albumin to the tube and keep it at 37 degrees Celsius for 30 minutes and after 30 minutes wash with three barceline.
  • Now add the drops of Coombs Serum in the tube of AHG Serum and mix well
  • Look for agglutination first without a microscope and then with the help of a microscope if necessary. In case of agglutination, the result will be positive.

This test is done in these cases.

If the blood groups are not matching in this matching.

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