The first 142 amino acids of glutamate decarboxylase do not contribute to epitopes recognized by autoantibodies associated with Type 1 diabetes

Glutamate decarboxylase (GAD) antibodies are the most widely used predictive marker for Type 1 diabetes, but many individuals currently found to be GAD antibody-positive are unlikely to develop diabetes. We have shown previously that radioimmunoassays using N-terminally truncated35S-GAD65(96-585) offer better disease specificity with similar sensitivity to full-length35S-GAD65(1-585). To determine whether assay performance could be improved further, we evaluated a more radically truncated35S-GAD65(143-585) radiolabel.