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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
Author(s) -
Ismail Heba M.,
EvansMolina Carmella,
DiMeglio Linda A.,
Becker Dorothy J.,
Libman Ingrid,
Sims Emily K.,
Boulware David,
Herold Kevan C.,
Rafkin Lisa,
Skyler Jay,
Cleves Mario A.,
Palmer Jerry,
Sosenko Jay M.
Publication year - 2019
Publication title -
pediatric diabetes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.678
H-Index - 75
eISSN - 1399-5448
pISSN - 1399-543X
DOI - 10.1111/pedi.12845
Subject(s) - c peptide , medicine , peptide , diabetes mellitus , area under the curve , type 1 diabetes , body mass index , endocrinology , biochemistry , biology
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 2 = 11.6% with AUC C‐peptide alone; R 2 = 20.0% with 120/30 C‐peptide added; R 2 = 13.7% with peak C‐peptide alone, R 2 = 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.