Pitfalls in laboratory testing for autoantibodies

: Quantitative autoantibody determination has recently can be widely used to confirm the diagnosis of autoimmune diseases, however, there are several problems with the assay methods. As pitfalls in terms of measurement methods, in this report we describe actual examples of a problem related to the analysis and of a large discrepancy between the data obtained by different methods of measurement. In the first example, the reaction solution in the microplate evaporated during the reaction process in automated analysis using an Eitest CA-RF ELISA kit, causing the values in the outermost wells to be significantly higher than in the inner wells. In the second example, there was a large discrepancy between the values obtained when the anti-dsDNA antibody of a systemic lupus erythematosus(SLE) patient was measured by radioimmunoassay(RIA) and by enzyme-linked immunosorbent assay(ELISA). The reason for the discrepancy in the second example may have been related to the method of the RIA, which used 50% ammonium sulfate in the B/F separation, and the possibility that certain patients have autoantibody that recognizes the ELISA solid-phase antigen more strongly. Accordingly, quantitative assay data for anti-dsDNA antibody, which possesses such diversity, should be evaluated with due consideration of the characteristics of the assay method and by checking them against the clinical data.