[Application of the gel test using and anti-IgA antiglobulin for the immunologic diagnosis of autoimmune hemolytic anemia with a negative direct Coombs test]. / Application du gel test utilisant une antiglobuline anti-IgA au diagnostic immunologique d'anémie hémolytique auto-immune à test de Coombs direct négatif.

Autoimmune hemolytic anemias (AIHA) are characterized by hyperhemolysis associated with the presence of the immunoglobulins IgG, IgM or IgA on the red cell membrane. These immunoglobulins react as auto-antibodies against the red cell auto-antigens of the patient. The diagnosis is supported by clinical and biological signs of hemolysis, and by the identification of the auto-antibodies using the direct antiglobulin test (DAT). Here we report 14 cases of patients who showed the clinical and biological profile of AIHA, but who gave a negative DAT. We therefore tried to determine the presence of IgA on the red cell membrane with a method more sensitive than the DAT: the gel test using anti-IgA. With such a gel test, we demonstrated that there were IgA auto-antibodies on the red cell membrane in the 14 cases, therefore confirming the diagnosis of AIHA. We discuss the interest of performing a gel test with anti-IgA in each case where AIHA is suspected, but in which a negative DAT has been observed.