Coombs Test

Clinical definition of the Coomb’s test
The Coombs' test is used to check for antibodies that act against the red blood cells in the body, may bind to them and hence cause premature red blood cell destruction (hemolysis). There are two forms of the Coombs' test: (a) Direct Coombs' test (b) Indirect Coombs' test

Why is the Coomb’s test done?
The Direct Coombs test is used to detect the antibodies that are bound to the surface of red blood cells. These antibodies sometimes destroy red blood cells and cause anemia. This test may be performed to diagnose the cause of autoimmune hemolytic anemia, jaundice or Rh disease in humans.
The indirect Coombs' test is used to check for unbound circulating antibodies in the serum sample, against a series of standardized red blood cells. The indirect Coombs test is generally used in prenatal testing of pregnant women and in testing blood prior to a blood transfusion or to determine if a person might have a reaction to a blood transfusion.

Who should do the Coomb’s test (Target population)?
The Coombs test may be used for the following cases:-

  • Detection of antibodies for the diagnosis of immune-mediated haemolytic anemias
  • Preparation of blood for transfusion in cross-matching, screening for atypical antibodies in the blood plasma of pregnant women as part of prenatal care

What should I do before the Coomb’s test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)

Venipuncture - Collection of blood from a vein, usually from the arm.

No Fasting Required.

No other special preparations required.

* Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my Coomb’s test results?

Reference Range*








Inference:  An abnormal (positive) Coombs' test indicates that the patient has antibodies that act against his/her own red blood cells which may be due to various reasons.

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the Coomb’s test

  • Autoimmune hemolytic anemia 
  • Drug-induced hemolytic anemia 
  • Erythroblastosis fetalis 
  • Infectious mononucleosis
  • Mycoplasmal infection
  • Syphilis
  • Chronic lymphocytic leukemia or other lymphoproliferative disorder
  • Systemic lupus erythematosus or another rheumatologic condition
  • Transfusion reaction, such as one due to improperly matched units of blood

Other tests related to the Coomb’s test

  • Blood Group
  • Rh antibody titer test
  • Antibody identification
  • Type and screen
  • Crossmatch

Synonyms : Direct/Indirect Antiglobulin test (DAT/IAT), Anti-human globulin test
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Coombs Test (Direct)