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Coomb’s Test (Direct)

About the test
What is this test done for?
A Coomb’s test is a blood test named after the person who invented it, Dr. Robin Coombs. It is performed to test the presence of antibodies, which may destroy red blood cells. This test is of two types: direct and indirect.
Why is it Done?
Coomb’s direct test is performed to detect the presence of certain antibodies in blood that cause our immune system to attack and destroy our red blood cells, like in the condition called hemolytic anemia. The direct test assesses the attached antibodies, whereas the indirect test assesses the floating or non-attached antibodies.
When should it be performed?

It is performed when one shows the signs and symptoms of suffering from hemolytic anemia:

  • Pale
  • Swelling in the entire body
  • Breathing difficulty
  • Enlarged spleen
  • Elevated levels of bilirubin, and thus, jaundice skin
  • During blood transfusion reaction, if there are fever and chills
How is it done
A blood sample will be collected from a vein in your arm. Fasting is not necessary prior to sample collection.

The direct Coomb’s test is positive in the following conditions:

  • Autoimmune hemolytic anemia.
  • Drug toxicity due to cephalosporins, levodopa, dapsone, nitrofurantoin, or NSAIDs
  • Transfusion reactions
  • Chronic lymphocytic leukemia
  • Mononucleosis
  • Infection with mycoplasma
  • Syphillis

The indirect Coomb’s test is abnormal in erythroblastosis fetalis.

Other Tests
Serum bilirubin is assessed. A complete blood count is also performed to assess hemoglobin levels.
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