A low GAD65 antibody titer does not significantly correlate with autoimmune neurological diseases, which has been confirmed by observations of patients with isolated type I diabetes and of healthy persons [136,137], whereas high GAD65 antibody titers (>20 nmol/L in CSF or in serum) are associated with autoimmune neurological diseases. This evidence concerns the gene GAD2 and type 1 diabetes mellitus.