title: HLA-DQB1 genotypes, islet antibodies and beta cell function in the classification of recent-onset diabetes among young adults in the nationwide Diabetes Incidence Study in Sweden.
abstract: OBJECTIVE
  The World Health Organization considers an aetiological classification of diabetes to be essential. The aim of this study was to evaluate whether HLA-DQB1 genotypes facilitate the classification of diabetes as compared with assessment of islet antibodies by investigating young adult diabetic patients.
  
  
  METHODS
  Blood samples were available at diagnosis for 1,872 (90%) of the 2,077 young adult patients (aged 15-34 years old) over a 5-year period in the nationwide Diabetes Incidence Study in Sweden. Islet antibodies were measured at diagnosis in 1,869 patients, fasting plasma C-peptide (fpC-peptide) after diagnosis in 1,522, while HLA-DQB1 genotypes were determined in 1,743.
  
  
  RESULTS
  Islet antibodies were found in 83% of patients clinically considered to have type 1 diabetes, 23% with type 2 diabetes and 45% with unclassifiable diabetes. After diagnosis, median fpC-peptide concentrations were markedly lower in patients with islet antibodies than in those without (0.24 vs 0.69 nmol/l, p<0.0001). Irrespective of clinical classification, patients with islet antibodies showed increased frequencies of at least one of the risk-associated HLA-DQB1 genotypes compared with patients without. Antibody-negative patients with risk-associated HLA-DQB1 genotypes had significantly lower median fpC-peptide concentrations than those without risk-associated genotypes (0.51 vs 0.74 nmol/l, p=0.0003).
  
  
  CONCLUSIONS
  Assessment of islet antibodies is necessary for the aetiological classification of diabetic patients. HLA-DQB1 genotyping does not improve the classification in patients with islet antibodies. However, in patients without islet antibodies, HLA-DQB1 genotyping together with C-peptide measurement may be of value in differentiating between idiopathic type 1 diabetes and type 2 diabetes.
authors.affiliation: Department of Clinical Sciences Malmö, Division of Endocrinology and Diabetes, Lund University, Malmö University Hospital, 205 02 Malmö, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Bakhtadze
authors.forename: H
authors.initials: H
authors.lastname: Borg
authors.forename: G
authors.initials: G
authors.lastname: Stenström
authors.forename: P
authors.initials: P
authors.lastname: Fernlund
authors.forename: H J
authors.initials: HJ
authors.lastname: Arnqvist
authors.forename: A
authors.initials: A
authors.lastname: Ekbom-Schnell
authors.forename: J
authors.initials: J
authors.lastname: Bolinder
authors.forename: J W
authors.initials: JW
authors.lastname: Eriksson
authors.forename: S
authors.initials: S
authors.lastname: Gudbjörnsdottir
authors.forename: L
authors.initials: L
authors.lastname: Nyström
authors.forename: L C
authors.initials: LC
authors.lastname: Groop
authors.forename: G
authors.initials: G
authors.lastname: Sundkvist
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000032:analysis*; D002096:C-Peptide / Q000097:blood; D017931:DNA Primers; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology; D005260:Female; D005838:Genotype; D005968:Glutamate Decarboxylase / Q000032:analysis; D006683:HLA-DQ Antigens / Q000235:genetics*; D059866:HLA-DQ beta-Chains; D006801:Humans; D050417:Insulin-Secreting Cells / Q000502:physiology*; D007527:Isoenzymes / Q000032:analysis; D008297:Male; D013548:Sweden / Q000453:epidemiology
chemical_list: D001323:Autoantibodies; D002096:C-Peptide; D017931:DNA Primers; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D007527:Isoenzymes; C024211:islet cell antibody; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2