Urinary C-peptide/creatinine ratio ‘useful measure’ of insulin secretion
MedWire News: A single urine C-peptide/creatinine ratio is a stable, reproducible measure of endogenous insulin secretion that correlates well with serum C-peptide following meal stimulation in patients with Type 2 diabetes, a study shows.
Furthermore, the authors say the association between the ratio of urinary C-peptide to creatinine and serum C-peptide exists even if there is moderate renal impairment.
Their study, published in Diabetic Medicine, supports the use of urinary C-peptide/creatinine ratio as a sensitive and specific alternative to serum C-peptide, which can be impractical for routine clinical use in settings where facilities for rapid analysis, centrifugation, and freezing of samples may be limited or unavailable, they say.
Led by Andrew Hattersley (Peninsula Medical School, Exeter, UK), the investigators analyzed fasting and postprandial urine and serum samples for C-peptide in 77 individuals with Type 2 diabetes (median age 68 years), 23 of whom had moderate renal impairment.
They used regression analysis to determine whether the association between urine C-peptide/creatinine ratio and serum C-peptide measurements differed between people with and without renal impairment.
The authors found that the reproducibility of urinary C-peptide/creatinine ratio in the fasting state and 2-hours post-meal was a mean of 28% and 26%, respectively, compared with corresponding values of 38% and 27% for serum C-peptide, respectively.
They also found that in patients with Type 2 diabetes, stimulated 120-min urinary C-peptide/creatinine ratio correlated well with post-meal 120-min stimulated serum C-peptide.
The association between urinary C-peptide/creatinine ratio and 0- to 120-min serum C-peptide did not differ between those with and without renal impairment.
However, fasting urinary C-peptide/creatinine ratio only weakly correlated with fasting serum C-peptide.
"A 120-min stimulated urine C-peptide/creatinine ratio is a stable, reproducible measure that is well correlated with serum C-peptide following meal stimulation, even if there is moderate renal impairment," say the authors.
They say the stability and non-invasiveness of single-sample urinary C-peptide/creatinine ratio could provide a means by which residual endogenous beta-cell function can be measured in settings without immediate access to a laboratory.
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By Sally Robertson