The influence of body mass index and age on C-peptide at the diagnosis of type 1 diabetes in children who participated in the diabetes prevention trial-type 1

Jay M. Sosenko, Susan Geyer, Jay S. Skyler, Lisa E. Rafkin, Heba M. Ismail, Ingrid M. Libman, Yuk Fun Liu, Linda A. DiMeglio, Carmella Evans-Molina, Jerry P. Palmer

Research output: Contribution to journalArticle

7 Scopus citations


Background/Objective: The extent of influence of BMI and age on C-peptide at the diagnosis of type 1 diabetes (T1D) is unknown. We thus studied the impact of body mass index Z-scores (BMIZ) and age on C-peptide measures at and soon after the diagnosis of T1D. Methods: Data from Diabetes Prevention Trial-Type 1 (DPT-1) participants <18.0 years at diagnosis was analyzed. Analyses examined associations of C-peptide measures with BMIZ and age in 2 cohorts: oral glucose tolerance tests (OGTTs) at diagnosis (n = 99) and mixed meal tolerance tests (MMTTs) <6 months after diagnosis (n = 80). Multivariable linear regression was utilized. Results: Fasting and area under the curve (AUC) C-peptide from OGTTs (n = 99) at diagnosis and MMTTs (n = 80) after diagnosis were positively associated with BMIZ and age (P <.001 for all). Associations persisted when BMIZ and age were included as independent variables in regression models (P <.001 for all). BMIZ and age explained 31%-47% of the variance of C-peptide measures. In an example, 2 individuals with identical AUC C-peptide values had an approximate 5-fold difference in values after adjustments for BMIZ and age. The association between fasting glucose and C-peptide decreased markedly when fasting C-peptide values were adjusted (r = 0.30, P <.01 to r = 0.07, n.s.). Conclusions: C-peptide measures are strongly and independently related to BMIZ and age at and soon after the diagnosis of T1D. Adjustments for BMIZ and age cause substantial changes in C-peptide values, and impact the association between glycemia and C-peptide. Such adjustments can improve assessments of β-cell impairment at diagnosis.

Original languageEnglish (US)
Pages (from-to)403-409
Number of pages7
JournalPediatric Diabetes
Issue number3
StatePublished - May 2018



  • C-peptide
  • age
  • body mass index
  • children
  • type 1 diabetes

ASJC Scopus subject areas

  • Internal Medicine
  • Pediatrics, Perinatology, and Child Health
  • Endocrinology, Diabetes and Metabolism

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