GAD(65) AUTOANTIBODIES INCREASE THE PREDICTABILITY BUT NOT THE SENSITIVITY OF ISLET-CELL AND INSULIN AUTOANTIBODIES FOR DEVELOPING INSULIN-DEPENDENT DIABETES-MELLITUS

The clinical onset of insulin-dependent diabetes (IDD) can be predicte d by determination of autoantibodies to several pancreatic-islet cell antigens. Islet-cell autoantibodies (ICA) and insulin autoantibodies ( AA) are most commonly used. We have developed a recombinant human glut amic acid decarboxylase (GAD(65)) radioimmunoassay and measured autoan tibodies to GAD(65) (GAD(65)A) in the sera of 73 documented prediabeti c individuals, 76 newly-diagnosed patients, 103 relatives of IDD proba nds at increased risk for the development of IDD because they were pos itive for ICA and/or IAA, 72 ICA and IAA negative relatives, and 207 h ealthy controls. Our data demonstrate that GAD(65)A are strongly assoc iated with the currently established autoantibody markers of IDD. Thei r presence in prediabetic subjects with only ICA or IAA enhances their risk for progression to IDD, yet does not much enhance the screening sensitivity already available through conventional ICA and IAA for IDD prediction.