The Coombs test is an immunoassay used to detect the presence of antibodies or antigens in the blood. It is used to diagnose a variety of conditions, including autoimmune hemolytic anemia, Rh incompatibility, and drug-induced immune hemolysis. There are two main types of Coombs tests: the direct Coombs test and the indirect Coombs test.
Direct Coombs Test
The direct Coombs test is also known as a direct antiglobulin test (DAT). It is used to detect the presence of antibodies attached to the red blood cells. Antibodies can be either IgG or complement proteins. The test is performed by adding antihuman globulin (AHG) to the sample. If antibodies are present, the AHG will bind to them, causing agglutination of the red blood cells.
Indirect Coombs Test
The indirect Coombs test is used to detect the presence of free antibodies in the serum of a patient. It is performed by mixing the patient’s serum with red blood cells of a known type. If antibodies are present, they will bind to the red blood cells, causing agglutination. The presence of agglutination indicates that the patient has antibodies in their serum.
