Do glutamic acid decarboxylase antibodies improve the prediction of IDDM in first-degree relatives at risk for IDDM?

Abstract

To determine whether the predictive value of islet cell antibodies (ICA) and insulin autoantibodies (IAA) is increased by measurement of glutamic acid decarboxylase antibodies (GADAb) in first-degree relatives of patients with insulin-dependent diabetes mellitus (IDDM), we measured GADAb in those developing IDDM and in relatives found to be ICA- or IAA-positive in our family screening study. First-degree relatives (n = 2904) were followed for 2.4 (median, range 0.04-5.8) years. Of the subjects developing IDDM, 11/14 (78%) had ICA ≥20JDF units, 1/14 (7%) had IAA ≥100 nU/ml and 6/14 (43%) had GADAb (≥460 nU/ml, measured by precipitation of enzymatic activity). Of the four subjects with ICA <20..