The Coombs' test is used in the investigation of haemolytic anaemia.
A positive Coombs' test is found in cases of autoimmune haemolysis due to the presence of IgG, complement or both, on the surface of the patient's red cells.
The principle of the Coombs' test is that addition of rabbit anti-human IgG to the patient's blood will result in aggregation of the patient's red cells if the red cells are coated in autoreactive IgG.
If antisera specific for complement components are added to the patient's blood the presence of complement on the red cells may be demonstrated.
Last reviewed 08/2021