Frequent Monitoring of C-Peptide Levels in Newly Diagnosed Type 1 Subjects Using Dried Blood Spots Collected at Home

Ruben H Willemsen, Keith Burling, Peter Barker, Fran Ackland, Renuka P Dias, Julie Edge, Anne Smith, John Todd, Boryana Lopez, Adrian P Mander, Catherine Guy, David B Dunger

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Objective: To evaluate an approach to measure β-cell function by frequent testing of C-peptide concentrations in dried blood spots (DBSs).

Patients: Thirty-two children, aged 7 to 17 years, with a recent diagnosis of type 1 diabetes.

Design: Mixed-meal tolerance test (MMTT) within 6 and again at 12 months after diagnosis, with paired venous and DBS C-peptide sampling at 0 and 90 minutes. Weekly DBS C-peptide before and after standardized breakfasts collected at home.

Results: DBS and plasma C-peptide levels (n = 115) correlated strongly (r = 0·91; P < 0.001). The Bland-Altman plot indicated good agreement. The median number of home-collected DBS cards per participant was 24 over a median of 6.9 months. Repeated DBS C-peptide levels varied considerably within and between subjects. Adjustment for corresponding home glucose measurements reduced the variance, permitting accurate description of changes over time. The correlation of the C-peptide slope over time (assessed by repeated home DBS) vs area under the curve during the two MMTTs was r = 0.73 (P < 0.001). Mixed models showed that a 1-month increase in diabetes duration was associated with 17-pmol/L decline in fasting DBS C-peptide, whereas increases of 1 mmol/L in glucose, 1 year older age at diagnosis, and 100 pmol/L higher baseline plasma C-peptide were associated with 18, 17, and 61 pmol/L higher fasting DBS C-peptide levels, respectively. In addition, glucose responsiveness decreased with longer diabetes duration.

Conclusion: Our approach permitted frequent assessment of C-peptide, making it feasible to monitor β-cell function at home. Evaluation of changes in the slope of C-peptide through this method may permit short-term evaluation of promising interventions.

Original languageEnglish
Pages (from-to)3350-3358
Number of pages9
JournalThe Journal of clinical endocrinology and metabolism
Issue number9
Publication statusPublished - 1 Sept 2018


  • Adolescent
  • Area Under Curve
  • Blood Glucose/analysis
  • Blood Glucose Self-Monitoring/statistics & numerical data
  • C-Peptide/blood
  • Child
  • Correlation of Data
  • Diabetes Mellitus, Type 1/blood
  • Dried Blood Spot Testing/methods
  • Fasting/blood
  • Feasibility Studies
  • Female
  • Humans
  • Male
  • Time Factors


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