Autoantibodies to glutamic acid decarboxylase in diabetic patients from a multi-ethnic Australian community: the Fremantle Diabetes Study

Aims To investigate ethnic/racial differences in the prevalence of serum antibodies to glutamic acid decarboxylase (GADA) and ICA512/IA-2 in diabetic patients from a large, urban community. Methods A cross-sectional sample of 1381 diabetic patients aged 11-98 years, representing 61% of those identified in a postcode-defined population base of 120 097 people were studied. Diabetes was classified on clinical grounds. Serum GADA and anti-ICA512/IA-2 were measured by radioimmunoprecipitation assay. Results Anglo-Celts formed 62% of the sample, southern Europeans 18%, other Europeans 8% and Asians 3%. GADA prevalence in Type 1 and Type 2 diabetes mellitus was 46.0% and 4.2%, respectively, amongst Anglo-Celts and 22.2% and 1.7% in southern Europeans. The prevalence of anti-ICA512/IA-2 in Type 1 diabetes was 17.4% and, in a sample of 233 patients with Type 2 diabetes, 0.8%. GADA-positive Type 2 patients had a lower body mass index and greater glycosylated haemoglobin, and were more likely to be taking insulin, than GADA-negative Type 2 diabetic subjects (P < 0.05), consistent with the phentoype of latent autoimmune diabetes of adults (LADA). In both Type 1 and Type 2 diabetes, there was a strong inverse association between GADA and serum triglycerides (P < 0.001). Conclusions The relatively low GADA prevalence in Angle-Celt patients with Type 1 diabetes is a feature of this community-based study and suggests that GADA levels do fall with time, given the older age of the sample and a relatively long period between diagnosis and sampling. Southern Europeans had an even lower GADA prevalence, regardless of diabetes type. Variations in GADA frequency in diabetic patients of differing European ethnicity has implications for clinical management and healthcare planning.