Abstract
Background: Estimation of insulin sensitivity (S(I)) and its daily variation are key for optimizing insulin therapy in patients with type 1 diabetes (T1D). We recently developed a method for S(I) estimation from continuous glucose monitoring (CGM) and continuous subcutaneous insulin infusion (CSII) data in adults with T1D (S(I)(SP)) and validated it under restrained experimental conditions. Herein, we validate in vivo a new version of S(I)(SP) performing well in daily life unrestrained conditions. Methods: The new S(I)(SP) was tested in both simulated and real data. The simulated dataset consists of 100 virtual adults of the UVa/Padova T1D Simulator monitored during an open-loop experiment, whereas the real dataset consists of 10 youths with T1D monitored during a hybrid closed-loop meal study. In both datasets, participants underwent two consecutive meals (breakfast and lunch, at 7 and 11 am) with the same carbohydrate content (70 g). Plasma glucose and insulin were measured during each meal to estimate the oral glucose minimal model S(I) (S(I)(MM)). CGM and CSII data were used for S(I)(SP) calculation, which was then validated against the gold standard S(I)(MM). Results: S(I)(SP) was estimated with good precision (median coefficient of variation <20%) in 100% of the real and 91% of the simulated meals. S(I)(SP) and S(I)(MM) were highly correlated, both in the simulated and real datasets (R = 0.82 and R = 0.83, P < 0.001), and exhibited a similar intraday pattern. Conclusions: S(I)(SP) is suitable for estimating S(I) in both closed- and open-loop settings, provided that the subject wears a CGM sensor and a subcutaneous insulin pump.