Hyperglycemic clamp and oral glucose tolerance test for 3-year prediction of clinical onset in persistently autoantibody-positive offspring and siblings of type 1 diabetic patients

Context and Objective: In preparation of future prevention trials, we aimed to identify predictors of 3-year diabetes onset among oral glucose tolerance test (OGTT)- and hyperglycemic clamp-derived metabolic markers in persistently islet autoantibody positive (autoAb+) offspring and siblings of patients with type 1 diabetes (T1D). Design: The design is a registry-based study. Setting: Functional tests were performed in a hospital setting. Participants: Persistently autoAb+ first-degree relatives of patients with T1D (n = 81; age 5-39 years). Main Outcome Measures: We assessed 3-year predictive ability of OGTT- and clamp-derived markers using receiver operating characteristics (ROC) and Cox regression analysis. Area underthe curve of clamp-derived first-phase C-peptide release (AUC5-10min; min 5-10) was determined in all relatives and second-phase release (AUC120-150min; min 120-150) in those aged 12-39years (n = 62). Results: Overall, the predictive ability of AUC5-10min was better than that of peak C-peptide, the best predictor among OGTT-derived parameters (ROC-AUC [95%CI]: 0.89 [0.80-0.98] vs 0.81 [0.70-0.93]). Fasting blood glucose (FBG) and AUC5-10min provided the best combination of markers for prediction of diabetes within 3 years; (ROC-AUC [95%CI]: 0.92 [0.84-1.00]). In multivariate Cox regression analysis, AUC5-10min (P = .001) was the strongest independent predictor and interacted significantly with all tested OGTT-derived parameters. AUC5-10min below percentile 10 of controls was associated with 50-70% progression to T1D regardless of age. Similar results were obtained for AUC120-150min. Conclusions: Clamp-derived first-phase C-peptide release can be used as an efficient and simple screening strategy in persistently autoAb+ offspring and siblings of T1D patients to predict impending diabetes. Copyright © 2015 by the Endocrine Society.