title: GAD antibodies in probands and their relatives in a cohort clinically selected for Type 2 diabetes.
abstract: OBJECTIVE
  A subset of patients who present as if they have Type 2 diabetes have positive pancreatic autoantibodies, and have been referred to as having latent autoimmune diabetes in adults (LADA). We assessed the prevalence and clinical characteristics of patients with glutamic acid decarboxylase antibodies (GADA) in a cohort clinically selected for Type 2 diabetes and determined the presence of diabetes and GADA in their first-degree relatives.
  
  
  METHODS
  GADA were measured in 2059 subjects, not known to be related, and clinically selected as having Type 2 diabetes for genetic studies. Clinical characteristics were compared in GADA positive and GADA negative subjects. Diabetes and GAD antibody status were compared in 208 first-degree relatives of GADA positive and GADA negative probands.
  
  
  RESULTS
  Of the subjects, 136 (7%) were GADA positive. Compared with the GADA negative subjects, they were slimmer (P < 0.001), diagnosed at a younger age (P = 0.011) and progressed to insulin faster (P < 0.001). Thirty-three per cent of GADA positive subjects had a first-degree relative with diabetes compared with 42% of GADA negative subjects (P = 0.034). The overall prevalence of GADA was similar in the first-degree relatives of GADA positive and GADA negative probands (4 v 5%), and 19 of 22 (86%) diabetic relatives of GADA positive probands were GADA negative.
  
  
  CONCLUSIONS
  Despite clinically selecting a Type 2 diabetes cohort, 7% were GADA positive with an altered phenotype. These GADA positive patients had a strong family history of non-autoimmune diabetes. This suggests that, in this subgroup of patients, autoimmune pancreatic beta-cell destruction occurs on a background of Type 2 diabetes genetic susceptibility.
authors.affiliation: Institute of Biomedical and Clinical Sciences, Peninsula Medical School, Exeter, UK.
authors.forename: H A J
authors.initials: HA
authors.lastname: Castleden
authors.forename: B
authors.initials: B
authors.lastname: Shields
authors.forename: P J
authors.initials: PJ
authors.lastname: Bingley
authors.forename: A J K
authors.initials: AJ
authors.lastname: Williams
authors.forename: M
authors.initials: M
authors.lastname: Sampson
authors.forename: M
authors.initials: M
authors.lastname: Walker
authors.forename: J M
authors.initials: JM
authors.lastname: Gibson
authors.forename: M I
authors.initials: MI
authors.lastname: McCarthy
authors.forename: G A
authors.initials: GA
authors.lastname: Hitman
authors.forename: J C
authors.initials: JC
authors.lastname: Levy
authors.forename: A T
authors.initials: AT
authors.lastname: Hattersley
authors.forename: B
authors.initials: B
authors.lastname: Vaidya
authors.forename: E R
authors.initials: ER
authors.lastname: Pearson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood*; D015551:Autoimmunity / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree
chemical_list: D000906:Antibodies; D005968:Glutamate Decarboxylase