Relative Contribution of Fasting Plasma and Postprandial Glucose to HbAlc and TIR in People with T1D on Basal-Bolus Insulin Therapy

Background: A recent report was published on the contribution of fasting plasma glucose (FPG) and postprandial glucose (PPG) to HbA1c and time in range (%TIR) in people with type 2 diabetes on multiple daily injection regimens using prandial Humalog® (Lispro). We extended this analysis to type 1 diabetes (T1D) using data from people randomized to 26 weeks of mealtime ultra rapid lispro (URLi; N=451), postmeal URLi (N=329) or mealtime Humalog (N=442) in the phase 3 trial, PRONTO-T1D, and its continuous glucose monitoring (CGM) substudy. Methods: A multivariate regression model was used to quantify the contribution of FPG and PPG change to the change in HbA1c and %TIR. The contribution of PPG relative to FPG was determined. %TIR was derived from 10-point self-monitored blood glucose (SMBG) and CGM data from the CGM substudy. Only results for the mealtime groups are presented here. Results: With URLi treatment, a 1 mmol/L reduction in FPG and PPG was associated with a 0.11% ± standard error 0.02% and 0.09% ± 0.01% reduction in HbA1c, respectively, both p<0.0001, with a contribution of PPG relative to FPG of 82%. Similar results were obtained with Humalog: A 1 mmol/L reduction in FPG and PPG was associated with reduction in HbA1c of 0.12% ± 0.02% and 0.07% ± 0.02%, respectively, both p<0.0001, but the contribution of PPG relative to FPG was 58%. For SMBG-derived %TIR, with URLi treatment, a 1 mmol/L reduction in FPG and PPG was associated with an increase in %TIR of 10.0% ± 0.53% and 8.6% ± 0.47%, respectively, all p<0.0001. Similarly, with Humalog, a 1 mmol/L reduction in FPG and PPG was associated with an increase in %TIR of 9.8% ± 0.56% and 8.6% ± 0.52%, respectively, all p<0.0001 A similar trend was observed with CGM data, although the absolute values of contributions of FPG and PPG differed. Conclusions: Changes in FPG and PPG significantly impacted HbA1c and %TIR in people with T1D, reinforcing the need to manage both FPG and PPG to achieve optimal glycemic control. Disclosure C. Piras de oliveira: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. M. A. Dellva: Employee; Self; Eli Lilly and Company. J. M. Bue-valleskey: Employee; Self; Eli Lilly and Company. A. M. Chang: Employee; Self; Eli Lilly and Company. F. B. Chigutsa: None. B. Liao: Employee; Self; Eli Lilly and Company. Funding Eli Lilly and Company