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Urine C-peptide creatinine ratio can be used to assess insulin resistance and insulin production in people without diabetes: an observational study
  1. Richard A Oram1,2,
  2. Andrew Rawlingson1,2,
  3. Beverley M Shields1,
  4. Coralie Bingham2,
  5. Rachel E J Besser,
  6. Tim J McDonald1,2,
  7. Bridget A Knight1,
  8. Andrew T Hattersley1
  1. 1NIHR Exeter Clinical Research Facility, University of Exeter Medical School, Royal Devon & Exeter NHS Foundation Trust, Exeter, UK
  2. 2Royal Devon & Exeter NHS Foundation Trust, Exeter, UK
  1. Correspondence to Dr Richard A Oram; r.oram{at}


Objectives The current assessment of insulin resistance (IR) in epidemiology studies relies on the blood measurement of C-peptide or insulin. A urine C-peptide creatinine ratio (UCPCR) can be posted from home unaided. It is validated against serum measures of the insulin in people with diabetes. We tested whether UCPCR could be a surrogate measure of IR by examining the correlation of UCPCR with serum insulin, C-peptide and HOMA2 (Homeostasis Model Assessment 2)-IR in participants without diabetes and with chronic kidney disease (CKD).

Design Observational study.

Setting Single-centre clinical research facility.

Participants 37 healthy volunteers and 30 patients with CKD (glomerular filtration rate 15–60) were recruited.

Primary and secondary endpoints Serum insulin, C-peptide and glucose at fasting (0), 30, 60, 90 and 120 min were measured during an oral glucose tolerance test (OGTT). Second-void fasting UCPCR and 120 min post-OGTT UCPCR were collected. HOMA2-IR was calculated using fasting insulin and glucose. The associations between UCPCR and serum measures were assessed using Spearman's correlations.

Results In healthy volunteers, fasting second-void UCPCR strongly correlated with serum insulin (rs=0.69, p<0.0001), C-peptide (rs=0.73, p<0.0001) and HOMA2-IR (rs=−0.69, p<0.0001). 120 min post-OGTT UCPCR correlated strongly with C-peptide and insulin area under the curve. In patients with CKD, UCPCR did not correlate with serum C-peptide, insulin or HOMA2-IR.

Conclusions In participants with normal renal function, UCPCR may be a simple, practical method for the assessment of IR in epidemiology studies.

  • Diabetes & Endocrinology
  • Statistics & Research Methods

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