GAD1 and type 1 diabetes mellitus: In this study we combined autoantibody and genetic data from 4 studies carried out in populations with a variable distribution of HLA genotypes to evaluate whether t-GADA identified more specifically individuals at risk for T1D than f-GADA and whether positivity for t-GADA or GAD epitope-specific autoantibodies were associated with HLA genotypes predisposing to T1D.