Clinical correlation of positive direct antiglobulin tests in patients with sickle cell disease

Serologic findings of immune-mediated hemolytic anemia (autoimmune hemolytic anemia and cold agglutinin disease) are not infrequent in patients with sickle cell disease and can he clinically significant. Features of sickle cell disease that may affect the emergence and intensity of immune-mediated hemolysis include the antigenic stimulation of chronic red blood cell (RBC) transfusions, increased autoantibody production, RBC membrane defects, and functional asplenism. We describe two patients with sickle cell disease and serologic findings of autoimmune hemolytic anemia, but only one had increased RBC destruction attributed to the autoantibody. That patient's RBCs had IgG and complement on the surface, while those of the other patient had IgG without complement. Functional asplenism may diminish the role of an IgG autoantibody that does not hind complement, since RBCs coated with complement are removed by the liver. Therefore, complement-binding autoantibodies may have particular significance in immune-mediated hemolysis in patients with sickle cell disease.