Coombs antibody is an anti-human globulin useful in testing for the presence of hemolysis. It was first described in 1945 by Robin Coombs, Mourant and Race. The test is used in screening blood prior to transfusion.

The test is used in two forms.

The direct Coombs test, or direct antiglobulin test, detects immunoproteins present on red blood cell membranes, by adding a polyspecific antiserum which contains antibodies specific for human immunoglobulins and complement to agglutinate the cells.

The indirect Coombs test, or indirect antiglobulin test, detects antibodies capable of attaching to normal red blood cells, by incubating normal red blood cells in the serum, washing the cells, and then using a polyspecific antiserum which contains antibodies specific for human immunoglobulins and complement to agglutinate the cells.