title: Fasting C-peptide and Related Parameters Characterizing Insulin Secretory Capacity for Correctly Classifying Diabetes Type and for Predicting Insulin Requirement in Patients with Type 2 Diabetes.
abstract: OBJECTIVE
  C-peptide allows estimation of insulin secretion even in the presence of insulin treatment. C-peptide may be suitable for the differential diagnosis of type 1 and type 2 diabetes, and, within type 2 diabetes, of insulin-requiring vs. non-insulin-requiring patients. Relating C-peptide concentrations to ambient glucose levels might improve its diagnostic potential.
  
  
  METHODS
  The diagnostic value (a) fasting C-peptide, (b) C-peptide/glucose ratios, and (c) the HOMA-ßC-peptide-index for predicting a diagnosis of type 1 (vs. type 2) diabetes were assessed.
  
  
  METHODS
  Specialised hospital for the care of diabetic patients (inpatient treatment). 303 patients with type 1 diabetes and 841 patients with type 2 diabetes.
  
  
  METHODS
  Odds ratios and 95% confidence intervals for a clinical diagnosis of type 1 diabetes or for insulin treatment by deciles of (a) fasting C-peptide, (b) C-peptide/glucose ratios, and (c) HOMA-ßC-peptide-index.
  
  
  RESULTS
  Low C-peptide concentrations were associated with a high odds ratio for type 1 diabetes and vice versa (p<0.0001). Concentrations of 0.13-0.36 nmol/l did not discriminate. C-peptide/glucose ratios or HOMA-ßC-Peptide did not perform better. The ability of all 3 parameters to predict the necessity for insulin treatment within the population of type 2-diabetic patients was low.
  
  
  CONCLUSIONS
  Fasting C-peptide and derived parameters help to differentiate type 1 from type 2 diabetes, but there is a range of C-peptide concentrations that does not help discriminate. Relating C-peptide to glucose did not improve diagnostic accuracy. C-peptide does not help predicting a need for insulin treatment in patients with type 2 diabetes.
authors.affiliation: Diabeteszentrum Bad Lauterberg (Harz), Germany (where work was performed).
authors.forename: F S
authors.initials: FS
authors.lastname: Becht
authors.affiliation: Diabeteszentrum Bad Lauterberg (Harz), Germany (where work was performed).
authors.forename: K
authors.initials: K
authors.lastname: Walther
authors.affiliation: Diabeteszentrum Bad Lauterberg (Harz), Germany (where work was performed).
authors.forename: E
authors.initials: E
authors.lastname: Martin
authors.affiliation: Diabeteszentrum Bad Lauterberg (Harz), Germany (where work was performed).
authors.forename: M A
authors.initials: MA
authors.lastname: Nauck
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000145:classification; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000145:classification; D005215:Fasting / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D002096:C-Peptide