GAD1 and diabetes mellitus: Comparable results were subsequently seen for isolated antibodies to GAD, IA-2/ICA512 or insulin in a number of family study populations [15–17], when samples from relatives screened for Diabetes Prevention Trial type 1 (DPT-1) were re-tested for these [3] and in 1,533 single antibody positive relatives included in an earlier TrialNet analysis [9].