Short Report: Metabolism Stimulated urine C-peptide creatinine ratio vs serumC-peptide level for monitoring of b-cell function in thefirst year after diagnosis of Type 1 diabetes

Aims
To determine if urine C-peptide/creatinine ratio is a useful tool for monitoring b-cell function in new-onset Type1 diabetes.

Methods Data were obtained from a prospective immunomodulation study in people with Type 1 diabetes ≤ 3 monthsfrom diagnosis, with a standard mixed-meal tolerance test and measurement of urine C-peptide/creatinine ratio carriedout at 0, 3, 6, 9 and 12 months. The change in the insulin-dose-adjusted HbA1clevel was also correlated with the changein serum/urine C-peptide level during the 12-month follow-up period.

Results A significant reduction in urine C-peptide/creatinine ratio, measured after a mixed-meal, was reached at9 months (-45.4%), whilst the reduction in stimulated serum C-peptide level reached significance after 3 months(-54.7%) in placebo-treated participants. Neither change in stimulated serum C-peptide nor change in urine C-peptidelevel correlated with each other, and nor did change in insulin-dose-adjusted HbA1clevel in the first 6 months, but allmeasures correlated significantly in the second half of the 12-month follow-up period.

Conclusion Mixed-meal-stimulated urine C-peptide/creatinine ratio was similar to, although less sensitive than,stimulated serum C-peptide level in monitoring b-cell function during the first year after diagnosis. Because the former issignificantly less invasive, it warrants inclusion in further studies in Type 1 diabetes and may represent an attractivealternative outcome measure in cohort studies and in children.