IgG4 subclass glutamic acid decarboxylase antibodies (GADA) are associated with a reduced risk of developing type 1 diabetes as well as increased C-peptide levels in GADA positive gestational diabetes.

Some women with gestational diabetes (GDM) present with autoantibodies associated with type 1 diabetes. These are usually directed against glutamic acid decarboxylase (GADA) and suggested to predict development of type 1 diabetes. The primary aim of this study was to investigate if GADA IgG subclasses at onset of GDM could assist in predicting postpartum development. Of 1225 women diagnosed with first-time GDM only 51 were GADA-positive. Total GADA was determined using ELISA. GADA subclasses were determined with radioimmunoassay. Approximately 25% of GADA-positive women developed type 1 diabetes postpartum. Titers of total GADA were higher in women that developed type 1 diabetes (142.1 vs 74.2u/mL; p=0.04) and they also had lower titers of GADA IgG4 (index=0.01 vs 0.04; p=0.03). In conclusion we found that that women with high titers of total GADA but low titers of GADA IgG4 were more prone to develop type 1 diabetes postpartum.