GAD2 and type 1 diabetes mellitus: Background and Purpose Three network laboratories measured antibodies to islet autoantigens.Antibodies to glutamic acid decarboxylase (GAD65 [GADA]) and the intracellularportion of protein tyrosine phosphatase (IA-2ic [IA-2A]) weremeasured by similar, but not identical, methods in samples from participants inthe Type 1 Diabetes Genetics Consortium (T1DGC).