Autoantibodies to the islet cell antigen SOX-13 are associated with duration but not type of diabetes

Aims The autoantigen SOX‐13 of the SRY‐related high mobility group box is a low‐frequency reactant in sera from patients with Type 1 diabetes. We further investigated the potential diagnostic role of anti‐SOX‐13, and in particular its ability to distinguish Type 1 from Type 2 diabetes, in two large, well‐characterized cohorts. Methods SOX‐13 autoantibody status was ascertained using a radioimmunoprecipitation assay in (i) a random sample of 546 participants in an Australian community‐based study (the Fremantle Diabetes Study; FDS) of whom 119 had Type 1 and 427 Type 2 diabetes, and (ii) a sample of 333 subjects with Type 2 diabetes from the United Kingdom Prospective Diabetes Study (UKPDS) stratified by age, anti‐glutamic acid decarboxylase (GAD) and islet cell antibody (ICA) status, and requirement for insulin therapy within 6 years of diagnosis. Results The frequencies of anti‐SOX‐13 in the FDS subjects were 16.0% and 14.8% for Type 1 and Type 2 patients, respectively, and levels were similar. In the UKPDS subjects, the frequency was 4.5%. In a logistic regression model involving demographic, anthropometric and metabolic variables, only diabetes duration was significantly associated with anti‐SOX‐13 positivity, especially for duration > 5 years (P