title: Home urine C-peptide creatinine ratio (UCPCR) testing can identify type 2 and MODY in pediatric diabetes.
abstract: BACKGROUND
  Making the correct diabetes diagnosis in children is crucial for lifelong management. Type 2 diabetes and maturity onset diabetes of the young (MODY) are seen in the pediatric setting, and can be difficult to discriminate from type 1 diabetes. Postprandial urinary C-peptide creatinine ratio (UCPCR) is a non-invasive measure of endogenous insulin secretion that has not been tested as a diagnostic tool in children or in patients with diabetes duration <5 yr. We aimed to assess whether UCPCR can discriminate type 1 diabetes from MODY and type 2 in pediatric diabetes.
  
  
  METHODS
  Two-hour postprandial UCPCR was measured in 264 patients aged <21 yr (type 1, n = 160; type 2, n = 41; and MODY, n = 63). Receiver operating characteristic curves were used to identify the optimal UCPCR cutoff for discriminating diabetes subtypes.
  
  
  RESULTS
  UCPCR was lower in type 1 diabetes [0.05 (<0.03-0.39) nmol/mmol median (interquartile range)] than in type 2 diabetes [4.01 (2.84-5.74) nmol/mmol, p < 0.0001] and MODY [3.51 (2.37-5.32) nmol/mmol, p < 0.0001]. UCPCR was similar in type 2 diabetes and MODY (p = 0.25), so patients were combined for subsequent analyses. After 2-yr duration, UCPCR ≥ 0.7 nmol/mmol has 100% sensitivity [95% confidence interval (CI): 92-100] and 97% specificity (95% CI: 91-99) for identifying non-type 1 (MODY + type 2 diabetes) from type 1 diabetes [area under the curve (AUC) 0.997]. UCPCR was poor at discriminating MODY from type 2 diabetes (AUC 0.57).
  
  
  CONCLUSIONS
  UCPCR testing can be used in diabetes duration greater than 2 yr to identify pediatric patients with non-type 1 diabetes. UCPCR testing is a practical non-invasive method for use in the pediatric outpatient setting.
authors.affiliation: Peninsula NIHR Clinical Research Facility, Peninsula Medical School, University of Exeter, Exeter, UK. rachel.besser@nhs.net
authors.forename: Rachel E J
authors.initials: RE
authors.lastname: Besser
authors.forename: Beverley M
authors.initials: BM
authors.lastname: Shields
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Hammersley
authors.forename: Kevin
authors.initials: K
authors.lastname: Colclough
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: McDonald
authors.forename: Zoe
authors.initials: Z
authors.lastname: Gray
authors.forename: James J N
authors.initials: JJ
authors.lastname: Heywood
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Barrett
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hattersley
mesh_terms: D000293:Adolescent; D000465:Algorithms; D002096:C-Peptide / Q000652:urine*; D002648:Child; D015331:Cohort Studies; D003404:Creatinine / Q000652:urine; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis / Q000503:physiopathology / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000503:physiopathology / Q000652:urine*; D003937:Diagnosis, Differential; D018450:Disease Progression; D015536:Down-Regulation; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D010044:Outpatient Clinics, Hospital; D019518:Postprandial Period; D012648:Self Care; D012680:Sensitivity and Specificity; D006113:United Kingdom
chemical_list: D002096:C-Peptide; D003404:Creatinine