GAD2 and type 1 diabetes mellitus: However, we adopted the same in-house RBA method that we have used in our laboratory for many years to assess autoantibodies against tissue transglutaminase, the screening marker for celiac disease (Agardh et al., 2003), as well as glutamic-acid decarboxylase 65 (GAD65) autoantibodies (Grubin et al., 1994) and zinc transporter 8 (ZnT8) to predict type 1 diabetes (Vaziri-Sani et al., 2010).