The value of gel test and ELAT in autoimmune haemolytic anaemia.

Abstract

Three methods for detection of warm type IgG autoantibody were evaluated using 400 blood samples from 147 patients suspected of autoimmune haemolytic anaemia (AIHA). Three direct antiglobulin techniques (DAT) were used: conventional tube DAT, gel-DAT by micromethod and gel-DAT enzyme linked antiglobulin test (ELAT). Eluate examinations confirmed the presence of autoantibodies on red cells. These tests were compared directly using 126 selected blood samples from 85 patients with IgG molecules on their red cells detected by the gel test. In 106 of these samples, collected from 65 patients with clinical symptoms of AIHA, the presence of autoantibody was confirmed by acid elution. The ELAT was positive in 100 samples (94%), 87 samples for tube DAT (82%). The ELAT as well as the tube DAT was negative in 20 samples with non-reactive eluates by gel test. The gel-DAT was therefore not fully specific and detected IgG on red cells of patients with hypergammaglobulinaemia. However, due its higher sensitivity it proved useful as a screening test. The ELAT allowed changes in the number of IgG molecules per red cell to be monitored quantitatively. Both methods play a part in the diagnosis and monitoring patients with warm type IgG auto-antibody.