Anti-GAD positivity (≥5 U/mL) was 69.0% in T1DM and 7.2% in T2DM; within T1DM, positivity declined with age (<13 compared with >35, p < 0.05; 13–19 compared with >35, p < 0.05) (Figure 4A). This evidence concerns the gene GAD1 and type 1 diabetes mellitus.