Glutamic acid decarboxylase antibodies (GADA) is the most important factor for prediction of insulin therapy within 3 years in young adult diabetic patients not classified as Type 1 diabetes on clinical grounds

Diabetes Metab Res Rev. 2000 Nov-Dec;16(6):442-47. doi: 10.1002/1520-7560(2000)9999:9999<::aid-dmrr152>;2-t.


Background: Differentiation between Type 1 and Type 2 diabetes in adults is difficult at diagnosis. In this study we tested the hypothesis that autoantibodies at diagnosis are predictive for insulin treatment within 3 years in patients initially not classified as Type 1 diabetes.

Methods: In a nationwide population-based study, blood samples were obtained from 764 patients, all diagnosed with diabetes during a 2-year period. At diagnosis, 583 (76%) were classified as Type 1, 110 (14%) as Type 2 and 71 (9.3%) could not be classified.

Results: Among patients not classified as Type 1 diabetes, 52 (47%) of Type 2 and 42 (59%) of unclassified patients were positive for islet cell antibodies (ICA), glutamic acid decarboxylase antibodies (GADA) or tyrosine phosphatase antibodies (IA-2A). These patients (n=94) had lower body mass index (BMI) (p<0.001) and lower C-peptide (p<0.001) compared to the autoantibody negative patients (n=87). Compared to clinically classified Type 1 diabetes patients positive for autoantibodies (n=477), they have higher BMI (p<0.001), higher C-peptide (p<0.001) and the same levels of ICA, GADA and IA-2A. After 3 years, 93% of autoantibody positive patients initially not classified as Type 1 were on insulin. When ICA, GADA, IA-2A, BMI and C-peptide were tested in a multiple logistic regression, only GADA was significant for insulin treatment within 3 years (OR=18.8; 95% CI 1.8-191) in patients treated with diet or oral drugs at diagnosis.

Conclusions: A correct classification is difficult in adult diabetic patients. The presence of pancreatic autoantibodies, especially GADA, at diagnosis of diabetes are highly predictive for insulin therapy within 3 years from diagnosis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Autoantibodies / blood*
  • Body Mass Index
  • C-Peptide / blood
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / classification*
  • Diabetes Mellitus, Type 1 / drug therapy*
  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / classification*
  • Diabetes Mellitus, Type 2 / drug therapy*
  • Diagnosis, Differential
  • Glutamate Decarboxylase / immunology*
  • Humans
  • Hypoglycemic Agents / therapeutic use*
  • Insulin / therapeutic use*
  • Islets of Langerhans / immunology
  • Isoenzymes / immunology*
  • Predictive Value of Tests
  • Sweden


  • Autoantibodies
  • C-Peptide
  • Hypoglycemic Agents
  • ICA512 autoantibody
  • Insulin
  • Isoenzymes
  • islet cell antibody
  • Glutamate Decarboxylase
  • glutamate decarboxylase 2