Unannounced Meal Challenges Using an Advanced Hybrid Closed-Loop System

Background: The advanced hybrid closed-loop (AHCL) algorithm combines automated basal rates and corrections yet requires meal announcement for optimal outcomes. We aimed to compare the performance of the MiniMed (TM) 780G AHCL algorithm with and without meal announcement.Methods: In a single-arm study involving 14 adults with type 1 diabetes, we evaluated the safety and efficacy of AHCL when meals were not announced. Participants stayed at a supervised environment for 5 days, during which the outcomes of not announcing meals (<= 80 g of carbohydrate) were assessed. Next, participants entered a 90-day at-home "unannounced" phase, during which all meals (<= 80 g of carbohydrate) were unannounced, followed by a 90-day at-home phase in which all meals were announced.Results: Time in range (TIR 70-180 mg/dL) was lower in the unannounced versus announced periods (67.5% +/- 12.5% vs. 77.7% +/- 9.5%; P < 0.01, respectively), with more time spent in hyperglycemia range 180-250 mg/dL (22.7% +/- 7.7% vs. 15.7% +/- 7.2%) and >250 mg/dL (7.9% +/- 6.4% vs. 3.6% +/- 2.7%), but less time in hypoglycemia range 54-70 mg/dL (1.6% +/- 1% vs. 2.8% +/- 1.8%) and <54 mg/dL (0.3% +/- 0.4% vs. 0.7% +/- 0.9%). Not announcing meals containing up to 60 g of carbohydrate did not lead to increase in postprandial extreme dysglycemia >250 mg/dL, and up to 20 g of unannounced carbohydrates did not significantly change the TIR 70-180 mg/dL compared with full announcement.Conclusion: The AHCL system is optimized for use with meal announcement. While not announcing meals of <= 80 g carbohydrates appears to be safe, it results in suboptimal postprandial glycemic control, especially with high-carbohydrate meals. Not announcing small meals (<= 20 g carbohydrate) does not deteriorate glycemic control.