Enzyme linked direct antiglobulin tests in patients with autoimmune haemolysis

Enzyme linked and agglutination direct antiglobulin tests were carried out on blood samples from 219 patients suspected of having autoimmune haemolysis. The enzyme linked tests were more sensitive: they could detect the small amounts of IgG, IgA, and IgM which are normally present on red cells and showed increased amounts of cell bound immunoglobulins in patients with Coombs test negative autoimmune haemolysis. Many patients had immunoglobulins of more than one class bound to their red cells; considering the degree of haemolysis in individual patients, it appeared that the different immunoglobulin classes acted synergistically in effecting red cell destruction, even in amounts too small to be detected by the agglutination tests. In patients with cold reacting autoantibodies and complement coating of the red cells active haemolysis was found (with one exception) where IgM was detected on the cells by the enzyme linked method. Elution studies indicated that immunoglobulins detected just by the enzyme linked techniques were red cell antibodies. Both enzyme linked and agglutination tests were negative in 66 patients: 61 of these had no evidence of haemolysis, and in the other five the haemolysis was not autoimmune in origin.