GAD1 and type 1 diabetes mellitus: The seroprevalence of GAD in T1D vs T2D was 21.3% vs 5.3%; IA-2A was 12.8% vs 2%; Any antibody positive 42.6% vs 7.3%; Both antibody positive 8.5% vs 0.***The seropositivity of GAD and IA-2 in the T2D groups reveals the need for population-specific islet autoantibody thresholds.***Double islet autoantibody positivity may be a better immunological T1D identification indicator.