title: Urine C-peptide creatinine ratio is a noninvasive alternative to the mixed-meal tolerance test in children and adults with type 1 diabetes.
abstract: OBJECTIVE
  Stimulated serum C-peptide (sCP) during a mixed-meal tolerance test (MMTT) is the gold standard measure of endogenous insulin secretion, but practical issues limit its use. We assessed urine C-peptide creatinine ratio (UCPCR) as an alternative.
  
  
  METHODS
  Seventy-two type 1 diabetic patients (age of diagnosis median 14 years [interquartile range 10-22]; diabetes duration 6.5 [2.3-32.7]) had an MMTT. sCP was collected at 90 min. Urine for UCPCR was collected at 120 min and following a home evening meal.
  
  
  RESULTS
  MMTT 120-min UCPCR was highly correlated to 90-min sCP (r = 0.97; P < 0.0001). UCPCR ≥ 0.53 nmol/mmol had 94% sensitivity/100% specificity for significant endogenous insulin secretion (90-min sCP ≥ 0.2 nmol/L). The 120-min postprandial evening meal UCPCR was highly correlated to 90-min sCP (r = 0.91; P < 0.0001). UCPCR ≥ 0.37 nmol/mmol had 84% sensitivity/97% specificity for sCP ≥ 0.2 nmol/L.
  
  
  CONCLUSIONS
  UCPCR testing is a sensitive and specific method for detecting insulin secretion. UCPCR may be a practical alternative to serum C-peptide testing, avoiding the need for inpatient investigation.
authors.affiliation: Peninsula National Institute for Health Research Clinical Research Facility, Peninsula Medical School, University of Exeter, Exeter, UK.
authors.forename: Rachel E J
authors.initials: RE
authors.lastname: Besser
authors.forename: Johnny
authors.initials: J
authors.lastname: Ludvigsson
authors.forename: Angus G
authors.initials: AG
authors.lastname: Jones
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: McDonald
authors.forename: Beverley M
authors.initials: BM
authors.lastname: Shields
authors.forename: Bridget A
authors.initials: BA
authors.lastname: Knight
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hattersley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002096:C-Peptide / Q000652:urine*; D003404:Creatinine / Q000652:urine*; D003922:Diabetes Mellitus, Type 1 / Q000652:urine*; D005260:Female; D005951:Glucose Tolerance Test / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D002096:C-Peptide; D003404:Creatinine