title: C-peptide in the classification of diabetes in children and adolescents.
abstract: OBJECTIVE
  To report C-peptide results in newly diagnosed patients and the relation to clinical diagnosis of diabetes.
  
  
  METHODS
  A nation-wide cohort, the Better Diabetes Diagnosis study was used to determine serum C-peptide at diagnosis in 2734 children and adolescents. Clinical data were collected at diagnosis and follow-up. C-peptide was determined in a validated and controlled time-resolved fluoroimmunoassay.
  
  
  RESULTS
  The clinical classification of diabetes, before any information on human leukocyte antigen, islet autoantibodies, or C-peptide was received, was type 1 diabetes (T1D) in 93%, type 2 diabetes (T2D) in 1.9%, maturity onset diabetes of the young (MODY) in 0.8%, secondary diabetes (0.6%), while 3.3% could not be classified. In a random, non-fasting serum sample at diagnosis, 56% of the patients had a C-peptide value >0.2 nmol/L. Children classified as T2D had the highest mean C-peptide (1.83 + 1.23 nmol/L) followed by MODY (1.04 ± 0.71 nmol/L) and T1D (0.28 ± 0.25 nmol/L). Only 1/1037 children who had C-peptide <0.2 nmol/L at diagnosis was classified with a type of diabetes other than T1D. Predictive value of C-peptide >1.0 nmol/L for the classification of either T2D or MODY was 0.46 [confidence interval 0.37-0.58].
  
  
  CONCLUSIONS
  More than half of children with newly diagnosed diabetes have clinically important residual beta-cell function. As the clinical diagnosis is not always straightforward, a random C-peptide taken at diagnosis may help to classify diabetes. There is an obvious use for C-peptide determinations to evaluate beta-cell function in children with diabetes.
authors.affiliation: Division of Pediatrics and Diabetes Research Center, Department of Clinical and Experimental Medicine, Linköping University Hospital, Linköping, Sweden. johnny.ludvigsson@lio.se
authors.forename: J
authors.initials: J
authors.lastname: Ludvigsson
authors.forename: A
authors.initials: A
authors.lastname: Carlsson
authors.forename: G
authors.initials: G
authors.lastname: Forsander
authors.forename: S
authors.initials: S
authors.lastname: Ivarsson
authors.forename: I
authors.initials: I
authors.lastname: Kockum
authors.forename: A
authors.initials: A
authors.lastname: Lernmark
authors.forename: B
authors.initials: B
authors.lastname: Lindblad
authors.forename: C
authors.initials: C
authors.lastname: Marcus
authors.forename: U
authors.initials: U
authors.lastname: Samuelsson
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D002096:C-Peptide / Q000032:analysis / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003920:Diabetes Mellitus / Q000097:blood* / Q000145:classification* / Q000453:epidemiology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000453:epidemiology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000453:epidemiology; D003940:Diagnostic Techniques, Endocrine; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009994:Osmolar Concentration; D011237:Predictive Value of Tests
chemical_list: D002096:C-Peptide