Mixed-Meal Tolerance Tests Vary for C-Peptide Response in Type 1 Diabetes

(HealthDay News) — Two- and 4-hour mixed-meal tolerance tests (MMTTs) vary for C-peptide responses in type 1 diabetes, according to research published in Diabetes Care.

Karen D. Boyle, from Rho Federal Systems Division in Chapel Hill, and colleagues examined the effect of abbreviating the MMTT test using data from 186 patients with type 1 diabetes participating in 3 clinical trials conducted by the Immune Tolerance Network. Data were included for up to 3 4-hour MMTTs for each patient, conducted yearly, for a total of 506 paired 2- and 4-hour observations. The 4-hour assessment was selected as the reference.

The researchers observed variation in the percent of the total 4-hour C-peptide area under the curve (AUC) captured in the first 2 hours, from 28% to 72%. The correlation between the 2- and 4-hour mean AUCs (mAUCs) was 0.98. The variability of the 2-hour test was generally greater than the 4-hour test; the variability was similar after adjustment for baseline. When the time to peak was less than 120 minutes, the 2-hour mAUC generally overestimated the 4-hour assessment, and vice versa for times greater than 120 minutes.

“Because the impact of the abbreviated test is differential over time and by age and treatment groups, estimates and significance tests for 2- and 4-hour assessments may be inconsistent,” the researchers wrote.

Reference

1. Boyle KD, Keyes-Elstein L, Ehlers MR, et al. Two- and Four-Hour Tests Differ in Capture of C-Peptide Responses to a Mixed Meal in Type 1 Diabetes. Diabetes Care. 2016. doi:10.2337/dc15-2077.