medwireNews: Transdermal capillary blood collection produces samples in which C-peptide can be reliably measured, removing the need for venous blood sampling, report researchers.
Presenting the findings, Rachel Besser (University of Oxford, UK) noted that the limitations of current blood sampling methods for C-peptide restrict its measurement in research studies and the clinic.
The investigators therefore tested a blood collection device based on a transdermal analyses patch. It uses an array of microneedles to rapidly puncture the skin and then vacuum extraction to draw up to 100 µL of capillary blood from the punctures into a lithium heparin-coated chamber. The procedure takes 2 to 3 minutes.
The device was tested in 71 children and adults with type 1 diabetes and 20 control volunteers, all of whom also underwent venous sampling for comparison. The median age of the participants with diabetes was 14.8 years, with the youngest being just 1.2 years of age, and 52.8% were female. The controls were a median age of 42.2 years and 95% were female, reflecting that most controls were the mothers of child participants.
On three occasions the device failed to take a blood sample; in the remaining 88 people it obtained a median of 50 µL plasma, Besser reported at the 15th ATTD conference in Barcelona, Spain.
The C-peptide levels ranged from undetectable to 2792 pmol/L, and were highly correlated with the levels obtained from matched venous blood samples. The capillary blood samples were 100% sensitive and specific for distinguishing between people who did and did not have venous C-peptide levels below 200 pmol/L.
Besser noted that capillary blood drawn using the study device “has the potential to be collected at home,” adding that it may be possible to measure islet autoantibodies by the same method, which the team is currently testing.
Of 70 study participants surveyed, 63% said they would prefer to have blood drawn using the transdermal device in future, while 7% opted for a venous blood draw and 30% were undecided.
Most participants found the transdermal capillary blood draw to be painless or only mildly painful. There was a tendency for older participants, especially the over 16s, to find venous blood sampling more painful than the transdermal procedure, whereas younger children rated the two procedures fairly equally.
Besser said: “I think what this reflects is that in our pediatric practice we tend to use numbing cream or cold spray […] and we aim not to cause pain with venous sampling.”
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