Abstract
The aim was to evaluate if the Dried Blood Spot (DBS)-technique can be used to analyse C-peptide. S-C-peptide and paired whole blood clotted on filters, dried, punched out and eluted were sampled from 198 healthy subjects. Six subjects with S-C-peptide values outside the reference range were excluded. A conversion formula using log-DBS-C-peptide was generated in a subset of 156 (∼80%) subjects with predictions made using also storage time (eluates) and age of subjects: (log S-C-peptide = 1.696 + 1.367 log DBS-C-peptide + 0.058 (storage time/month) + 0.014 (age/10 years). This formula was cross validated into the original population. Using Bland-Altman plots, mean difference between converted log DBS-C-peptide and log S-C-peptide at baseline was 0 and limits of agreements were −0.18 to +0.18. Mean difference between converted log DBS-C-peptide values after six months and log S-C-peptide value from baseline was −0.01 and limits of agreement were −0.20–0.19. The lowest value detected with the DBS-technique corresponded to serum C-peptide 0.44 nmol/L. We concluded that DBS-C-peptide can be used as a first line screening test to monitor normal beta cell function. C-peptide on filters remained stable for six months.
Acknowledgements
The authors wish to acknowledge the expert technical assistance from Gunilla Lindahl, Pia Svensson, Ann Radelius and Barbro Palmqvist.
Dr Kristian Lynch, Department of Pediatrics Epidemiology Center, University of South Florida, Tampa, Florida, US is thanked for statistical advice.
Source of support: The Royal Physiographic Society in Lund, Sweden. The Novo Nordisk Foundation, Denmark and The Knut and Alice Wallenberg Foundation, Sweden, are acknowledged for research grants contributing to this study.
Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.