Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Objective: C-peptide and islet autoantibodies are key type 1 diabetes biomarkers, typically requiring venous sampling, which limit their utility. We assessed transdermal capillary blood (TCB) collection as a practical alternative. Research Design and methods: Ninety-one individuals (71 type 1 diabetes, 20 controls; type 1 diabetes: aged median 14.8 years[interquartile range 9.1-17.1]; diabetes duration 4.0 years[1.5-7.7]; controls 42.2 years[38.0-52.1]) underwent contemporaneous venous and TCB sampling for measurement of plasma C-peptide. Type 1 diabetes participants also provided venous serum and plasma, and TCB plasma for measurement of autoantibodies to glutamate decarboxylase, islet antigen-2, and zinc transporter 8. The ability of TCB plasma to detect significant endogenous insulin secretion (venous C-peptide ≥200pmol/L) was compared along with agreement in levels using Bland-Altman. Venous serum was compared with venous and TCB plasma for detection of autoantibodies using established thresholds. Acceptability was assessed by age-appropriate questionnaire.Results: Transdermal sampling took a mean of 2.35minutes (SD 1.49). Median sample volume was 50 µl(IQR 40-50) with 3/91(3.3%) failures, and 13/88(14.7%) <35 µL). TCB C-peptide showed good agreement to venous plasma (mean venous ln(C-peptide) – TCB ln(C-peptide) = 0.008, 95% CI(-0.23, 0.29), with 100%(36/36) sensitivity/100%(50/50) specificity to detect venous C-peptide ≥ 200pmol/L. Where venous serum in multiple autoantibody positive TCB plasma agreed in 22/32 (sensitivity 69%), comparative specificity was 35/36 (97%). TCB was preferred to venous sampling (type 1 diabetes: 63% vs 7%; 30% undecided). Conclusions: Transdermal capillary testing for C-peptide is a sensitive, specific, and acceptable alternative to venous sampling, TCB sampling for islet autoantibodies needs further assessment.


Journal article


Diabetes Care


American Diabetes Association

Publication Date