Mixed‐meal tolerance test to assess residual beta‐cell secretion: Beyond the area‐under‐curve of plasma C‐peptide concentration

AIMS: Residual beta‐cell secretion in type 1 diabetes is commonly assessed by area‐under‐curve of plasma C‐peptide concentration (AUC(Cpep)) following mixed‐meal tolerance test (MMTT). We aimed to investigate alternative measures of beta‐cell responsiveness. METHODS: We analyzed data from 32 youth (age 7 to 17 years) undergoing MMTT within 6 months of type 1 diabetes diagnosis. We related AUC(Cpep) with (a) validated mechanistic index of postprandial beta‐cell responsiveness M (I) accounting for glucose level during MMTT, and (b) pragmatic marker calculated as baseline plasma C‐peptide concentration corrected for baseline plasma glucose concentration. RESULTS: Postprandial responsiveness M (I) was correlated with age and BMI SDS (R (s) = 0.66 and 0.44, P < 0.01 and P < 0.05) and was more correlated with glycated hemoglobin than AUC(Cpep) (R (s) = 0.79, P = 0.04). The pragmatic marker was highly correlated with AUC(Cpep) (R (s) = 0.94, P < 0.01). CONCLUSIONS: Postprandial responsiveness M (I) may be more relevant to glucose control than AUC(Cpep). Baseline C‐peptide corrected for baseline glucose appears to be a suitable surrogate of AUC(Cpep) if MMTT is not performed.