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Predictability of C‐peptide for autoimmune diabetes in young adult diabetic patients

2001; Wiley; Volume: 18; Issue: 3 Linguagem: Inglês

10.1002/pdi.125

2047-2900

Carina Törn, Mona Landin‐Olsson, Bengt Scherstén,

Metabolism, Diabetes, and Cancer

Abstract C‐peptide is measured to evaluate the endogenous insulin production. Since the secretion of both insulin and C‐peptide are stimulated by food intake, the sampling procedure is standardized to fasting conditions. The aim of this study was to evaluate the difference in C‐peptide levels in fasting and non‐fasting states in diabetic patients and also to investigate the use of fasting and non‐fasting C‐peptide as instruments to discriminate between diabetes with autoimmune markers (islet cell antibodies, glutamic acid decarboxylase antibodies or antibodies against tyrosine phosphatase) and without autoimmune markers at diagnosis. In patients with autoimmune markers, the median level of C‐peptide was slightly lower in the fasting state ( n =283; 0.27; 0.16–0.36 nmol/L) compared to C‐peptide levels in the non‐fasting state ( n =138; 0.30; 0.20–0.52 nmol/L; p =0.0066). In patients without autoimmune markers, C‐peptide levels were lower in fasting patients ( n =105; 0.51; 0.28–0.76 nmol/L) compared to non‐fasting patients ( n =38; 0.74; 0.39–1.1 nmol/L; p =0.011). The highest positive predictive value (94%) for autoimmune diabetes was observed for a C‐peptide below 0.30 nmol/L in the non‐fasting condition. We conclude that C‐peptide can be taken either fasting or randomly in patients with type 1 diabetes since the beta cell function was stimulated only to a limited extent by food intake. At the time of diagnosis, C‐peptide can prefarably be taken randomly during the day since this improves the discrimination between patients with and without autoimmune markers. Copyright © 2001 John Wiley & Sons, Ltd.