title: Autoantibodies to IA-2 and GAD65 in patients with type 2 diabetes mellitus of varied duration: prevalence and correlation with clinical features.
abstract: OBJECTIVE
  To determine the prevalence of autoantibodies to IA-2 (IA-2Ab) and glutamic acid decarboxylase (GADAb) in type 2 diabetes, their relationship to disease duration, and their importance in management decisions.
  
  
  METHODS
  We undertook a study of 101 patients with type 2 diabetes (defined as nonketotic hyperglycemia at diagnosis) of varied duration (median, 4 years). Results were compared with those from 36 patients with type 1 diabetes also of varied duration (median, 2 years). IA-2Ab and GADAb were measured by radioligand-binding assays with use of in vitro-synthesized, 35S-labeled antigens.
  
  
  RESULTS
  Of the 101 patients with type 2 diabetes, 20 (20%) were positive for GADAb; only 4 of these 20 were positive for IA-2Ab. In comparison, 75% of patients with type 1 diabetes were positive for GADAb, IA-2Ab, or both (P<0.0001). The coincidence of IA-2Ab positivity in GADAb-positive patients with type 2 diabetes was significantly lower than in patients with type 1 diabetes (20% versus 73%, respectively; P = 0.002). All four IA-2Ab- and GADAb-positive patients with type 2 diabetes required insulin and were younger than those positive for GADAb alone (P = 0.018). GADAb positivity in patients with type 2 diabetes was highly associated with insulin requirement (P = 0.004), with an odds ratio of 5.8 in predicting insulin dependence. Among patients with type 2 diabetes receiving insulin therapy, disease duration was significantly shorter (P = 0.025) and body mass index was significantly lower (P<0.001) in GADAb-positive versus GADAb-negative patients. In contrast to type 1 diabetes, in which GADAb values were negatively correlated with disease duration (r = -0.34; P = 0.044), no significant correlation with disease duration was observed in type 2 diabetes (r = -0.166; P = 0.48).
  
  
  CONCLUSIONS
  Irrespective of duration of disease, measurement of IA-2Ab and GADAb can help to identify those patients with type 2 diabetes most likely to require insulin therapy.
authors.affiliation: Department of Clinical Pathology, L30, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
authors.forename: Y Z
authors.initials: YZ
authors.lastname: Grasso
authors.forename: S K
authors.initials: SK
authors.lastname: Reddy
authors.forename: C R
authors.initials: CR
authors.lastname: Rosenfeld
authors.forename: W I
authors.initials: WI
authors.lastname: Hussein
authors.forename: B J
authors.initials: BJ
authors.lastname: Hoogwerf
authors.forename: C
authors.initials: C
authors.lastname: Faiman
authors.forename: M K
authors.initials: MK
authors.lastname: Gupta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology; D003924:Diabetes Mellitus, Type 2 / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology*; D006801:Humans; D007527:Isoenzymes / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D001323:Autoantibodies; C096322:ICA512 autoantibody; D007527:Isoenzymes; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2