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Associations of HbA1c with the timing of C-peptide responses during the oral glucose tolerance test at the diagnosis of type 1 diabetes.

Citation
Ismail, H. M., et al. “Associations Of Hba1C With The Timing Of C-Peptide Responses During The Oral Glucose Tolerance Test At The Diagnosis Of Type 1 Diabetes.”. Pediatric Diabetes, pp. 408-413.
Center University of Washington Yale University
Multicenter
Multicenter
Author Heba M Ismail, Carmella Evans-Molina, Linda A DiMeglio, Dorothy J Becker, Ingrid Libman, Emily K Sims, David Boulware, Kevan C Herold, Lisa Rafkin, Jay Skyler, Mario A Cleves, Jerry Palmer, Jay M Sosenko, Type 1 Diabetes Trial Net and Diabetes Prevention Trial-Type-1 Study Groups
Keywords C-peptide, HbA1c, OGTT, glycemia, type 1 diabetes
Abstract

BACKGROUND: In new onset type 1 diabetes (T1D), overall C-peptide measures such as area under the curve (AUC) C-peptide and peak C-peptide are useful for estimating the extent of β-cell dysfunction, and for assessing responses to intervention therapy. However, measures of the timing of C-peptide responsiveness could have additional value.

OBJECTIVES: We assessed the contribution of the timing of C-peptide responsiveness during oral glucose tolerance tests (OGTTs) to hemoglobin A1c (HbA1c) variation at T1D diagnosis.

METHODS: We analyzed data from 85 individuals <18 years with OGTTs and HbA1c measurements at diagnosis. Overall [AUC and peak C-peptide] and timing measures [30-0 minute C-peptide (early); 60 to 120 minute C-peptide sum-30 minutes (late); 120/30 C-peptide; time to peak C-peptide] were utilized.

RESULTS: At diagnosis, the mean (±SD) age was 11.2 ± 3.3 years, body mass index (BMI)-z was 0.4 ± 1.1, 51.0% were male. The average HbA1c was 43.54 ± 8.46 mmol/mol (6.1 ± 0.8%). HbA1c correlated inversely with the AUC C-peptide (P < 0.001), peak C-peptide (P < 0.001), early and late C-peptide responses (P < 0.001 each), and 120/30 C-peptide (P < 0.001). Those with a peak C-peptide occurring at ≤60 minutes had higher HbA1c values than those with peaks later (P = 0.003). HbA1c variance was better explained with timing measures added to regression models (R  = 11.6% with AUC C-peptide alone; R  = 20.0% with 120/30 C-peptide added; R  = 13.7% with peak C-peptide alone, R  = 20.4% with timing of the peak added). Similar associations were seen between the 2-hour glucose and the C-peptide measures.

CONCLUSIONS: These findings show that the addition of timing measures of C-peptide responsiveness better explains HbA1c variation at diagnosis than standard measures alone.

Year of Publication
2019
Journal
Pediatric diabetes
Volume
20
Issue
4
Number of Pages
408-413
Date Published
12/2019
ISSN Number
1399-5448
DOI
10.1111/pedi.12845
Alternate Journal
Pediatr Diabetes
PMID
30891858
PMCID
PMC6655420
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