Development of measurement method for autoantibodies against red blood cells by flow cytometric analysis

Abstract

Autoimmune hemolytic anemia (AIHA) is a disease in which red blood cells are damaged by autoantibodies that react with antigens on the red blood cell membrane causing hemolysis. The direct antiglobulin test (DAT) has become the gold standard for the diagnosis of AIHA, and if the result is positive, the diagnosis of AIHA is relatively easily established. However, some cases of AIHA show negative DAT results; therefore, diagnosis based on DAT results only is infeasible. Quantification of red blood cell-bound IgG (RBC-IgG) is useful in such cases. The RBC-IgG measurement has mainly been by the RIA method, but it is difficult to introduce it as a routine method owing to problems related to radioactivity. Considering this background, we studied a method of measuring RBC-IgG by flow cytometry and used the mean fluorescence intensity difference (MFID) as an indicator of RBC-IgG. For DAT-negative samples, we successfully set a reference range for MFID and confirmed its usefulness in the diagnosis of AIHA.