Urine C-Peptide Creatinine Ratio Is a Noninvasive Alternative to the Mixed-Meal Tolerance Test in Children and Adults With Type 1 Diabetes

Peninsula National Institute for Health Research Clinical Research Facility, Peninsula Medical School, University of Exeter, Exeter, UK.
Diabetes care (Impact Factor: 8.42). 02/2011; 34(3):607-9. DOI: 10.2337/dc10-2114
Source: PubMed


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.
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.
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.
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.

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    • "The urine sample was collected in a standard mid‐stream urine boric acid‐containing specimen pot, and returned by post to the routine pathology laboratories for UCPCR analysis. UCPCR ≤ 0.2 nmol/mmol is equivalent to a stimulated serum C‐peptide (sSCP) of 0.2 nmol/l in an MMTT 15, representing an absence of clinically significant insulin secretion 11. This level is associated with unstable glycaemia, increased risk of hypoglycaemia and microvascular complications (as well as absolute insulin requirement) in Type 1 diabetes 11. "
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