Direct Coombs Test in Dehradun

What is a Direct Coombs Test?

The direct Coombs test, more properly the direct antiglobulin test, looks for antibodies stuck to the surface of your own red blood cells. Its logic is straightforward: if the immune system has coated red cells with antibody, those cells are marked for destruction, and the spleen removes them faster than the marrow can replace them, producing an immune haemolytic anaemia. A reagent is added that bridges between antibody-coated cells and makes them clump visibly. It answers a specific and important question in an anaemic patient: is this anaemia caused by the immune system destroying red cells, as opposed to deficiency, blood loss or reduced production. That distinction changes management completely, since immune haemolysis is treated with steroids and other immunosuppression rather than iron. It is also the test that identifies haemolytic disease of the newborn, where maternal antibodies have crossed the placenta and are destroying the baby's red cells, and it is used to investigate a transfusion reaction, where donor cells are being attacked.

Why take this test?

A direct Coombs test is advised for anaemia accompanied by signs of red cell destruction: jaundice, dark urine, an enlarged spleen, a raised indirect bilirubin, a raised reticulocyte count or a low haptoglobin. It is essential in a newborn with jaundice appearing in the first 24 hours or rising unusually fast, particularly where the mother is Rh negative or of a different blood group, since haemolytic disease of the newborn needs prompt treatment. It is used to investigate a suspected transfusion reaction, and in autoimmune conditions such as lupus, in chronic lymphocytic leukaemia and lymphomas, and where certain medicines are suspected of triggering immune haemolysis. It is not a general screening test and is ordered in response to a specific clinical picture, usually alongside a full blood count, reticulocyte count, bilirubin and a peripheral smear, since it is the combination that establishes haemolysis and its cause.

• Anaemia with jaundice, dark urine or an enlarged spleen
• A raised reticulocyte count with a raised indirect bilirubin
• Newborn jaundice appearing early or rising rapidly
• Suspected haemolytic disease of the newborn
• Investigating a suspected transfusion reaction
• Suspected drug-induced or autoimmune haemolysis

FAQs: Direct Coombs Test in Dehradun