The
enzyme-linked antiglobulin test (ELAT) was employed to measure the number of
IgG molecules per red blood cell (
IgG/RBC) in 11 patients with
autoimmune hemolytic anemia (AIHA). All patients with AIHA had high levels of red cell-associated
IgG (110-3, 650
IgG/RBC). The control group consisted of normal volunteers (N = 10) and patients with
hereditary spherocytosis (N = 1), beta 0-thalassemia (N = 1), immunologic
thrombocytopenic purpura (N = 3) and
IgG multiple myeloma (N = 4). All control individuals presented low levels of red cell
IgG (less than 38
IgG/RBC) with the exception of one of four patients with myeloma who had a mildly elevated value (50
IgG/RBC). Since the
multiple myeloma patients had greater than 2 g/dl
IgG, the possible nonspecific uptake of
IgG onto the RBCs of patients with elevated serum
IgG values did not interfere with the results of ELAT. ELAT proved to be a useful method for accurate quantification of the amount of
IgG specifically bound on the surface of RBC of patients with AIHA.