Insulin autoantibodies measured by radioimmunoassay methodology are more related to insulin-dependent diabetes mellitus than those measured by enzyme-linked immunosorbent assay: results of the Fourth International Workshop on the Standardization of Insulin Autoantibody Measurement.

Abstract

Insulin autoantibodies (IAA) have been identified in newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients and in individuals at high risk of developing the disease. However, the literature is not in agreement regarding the prevalence, significance, and predictive value of IAA. Previous workshops have shown that certain sera give markedly different results depending upon assay methodology and, therefore, have suggested that these discrepancies may be due to variations in the assay methodologies used: either the fluid phase RIA or the solid phase enzyme-linked immunosorbent assay (ELISA). Sera from controls (n = 61), newly diagnosed IDDM patients (n = 30), healthy subjects who later became diabetic (n = 8), and first degree relatives of diabetic probands (n = 22) were randomly numbered and sent without category identification to 19 RIA and 10 ELISA laboratories. Each laboratory's raw data from the control sera were used to determine the cut-off point for positive (3 SD above the mean of control sera) in the disease relevant categories. RIA and ELISA methods were comparable in obtaining a low frequency of IAA in control sera. However, the laboratories using RIA methods found a much higher percentage of sera to be IAA positive among both newly diagnosed patients and healthy individuals who later developed diabetes than laboratories using ELISA methods (P less than 0.005). In contrast, there was considerable overlap in the percentage of sera from first degree relatives found positive by both assays. These data strongly suggest that IAA measured by RIA methodology are more disease related than those measured by ELISA methods. Consequently, RIA assays or assays proven to perform as well should be used to measure IAA associated with IDDM.

Early expression of antiinsulin autoantibodies of humans and the NOD mouse: Evidence for early determination of subsequent diabetes

“…Prior workshops indicated that IAA measured by ELISA techniques did not detect IAA associated with diabetes risk, and, thus, most investigators have utilized fluid phase radioassays (16). The volume of sera necessary for high sensitivity radioassays, with polyethylene glycol precipitation and centrifugation followed by ␥ counting, have limited the determination of IAA (2).…”

The molecular specificity of insulin autoantibodies

“…First, there has been a notable lack of correlation between results of IAA measured in ELISA and RBA assays [104]. Autoantibodies such as anti-DNA [105], anticardiolipin [106] or anti-GAD [107], on the other hand, show close agreement in the two systems.…”

“…The disease speci®city of the ELISA and RBA systems has only been formally compared with diabetes-related sera [104] though many examples of non-diabetic sera in which IAA are detected by both ELISA and RBA have been described [83,87]. Thus, Castano and colleagues studied only diabetes-related IAA + sera and concluded that there were no differences in the binding characteristics of IA and IAA to a panel of insulin variants [110].…”

Cellular and molecular pathogenesis of type 1A diabetes

“…Currently, multiple sequenced autoantigens have been discovered and autoantibodies are measured with recombinant autoantibody assays [1,2,53]. The standard assays measure autoantibodies reacting with insulin [54][55][56][57][58][59][60], glutamic acid decarboxylase (GAD) [61], ICA512/IA-2 [62,63], and I-A2 beta (phogrin) [64,65]. Despite the importance of autoantibodies for disease prediction, anti-islet autoantibodies do not by themselves cause b-cell destruction.…”