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

  1. Andrew T. Hattersley, DM1
  1. 1Peninsula National Institute for Health Research Clinical Research Facility, Peninsula Medical School, University of Exeter, Exeter, U.K.
  2. 2Division of Pediatrics, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
  3. 3Department of Clinical Biochemistry, Royal Devon & Exeter NHS Foundation Trust, Exeter, U.K.
  1. Corresponding author: Andrew T. Hattersley, andrew.hattersley{at}pms.ac.uk.
  1. R.E.J.B. and J.L. contributed equally to this study.

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.

RESEARCH DESIGN AND METHODS Seventy-two type 1 diabetic patients (diagnosed median 14 years [interquartile range 10–22] previously; 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 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.

Footnotes

    • Received November 9, 2010.
    • Accepted December 11, 2010.

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