Simplified Meal Announcement Study (SMASH) Using Hybrid Closed-Loop Insulin Delivery in Youth and Young Adults with Type 1 Diabetes – A Randomised Controlled Two-Centre Crossover Trial

Abstract

BackgroundThe majority of hybrid closed-loop (HCL) systems still require exact carbohydrate counting (ECC) but there is little evidence on its glycaemic relevance. We aimed to compare HCL glucose control with simplified meal announcement (SMA) vs ECC in youth and young adults with type 1 diabetes using the mylife CamAPS FX system.MethodsThis two-centre, randomised crossover, non-inferiority trial recruited 46 participants (aged 12-20 years) with type 1 diabetes using multiple daily injections (n=35), sensor-augmented pump (n=4) or HCL pump (n=7) therapy before enrolment. They were randomly assigned to HCL therapy (CamAPS FX algorithm, YpsoPump, Dexcom G6) with SMA (individualized meal-specific carbohydrate amounts) first and ECC second, or vice versa, in random order, each for three months. The primary endpoint was the percentage time with sensor glucose in target range (3·9-10·0mmol/l) with a non-inferiority margin of 5 percentage points. Secondary endpoints were other sensor glucose endpoints, insulin metrics, usability and safety endpoints. The study was pre-registered on ClinicalTrials.gov, NCT05481034.FindingsForty-three participants (18 females) completed the trial. In the intention-to-treat analysis, percentage time in target range (mean±SD) was 69·9±12·4% with SMA and 70·7±13·0% with ECC (estimated mean difference -0·6 percentage points (95% CI -2·4;1·1), demonstrating non-inferiority). Percentage time <3·9mmol/l (median [IQR] 1·8 [1·2;2·2]% vs 1·9 [1·6;2·5]%) and >10·0mmol/l (28·2±12·6% vs 27·2±13·4%) were similar between periods. Total daily insulin dose was higher in SMA (54·0±14·7U vs 51·7±12·1U, p=0·037). One serious adverse event occurred in the SMA and two in the ECC, none of which were intervention-related.InterpretationGlucose control using the CamAPS FX algorithm with SMA was non-inferior to its use with ECC in youth and young adults with type 1 diabetes, challenging the justification for exact carbohydrate quantification in this population.FundingSwiss Diabetes Foundation, Bangerter-Rhyner Foundation and Swiss Academy of Medical Sciences. Product support from Dexcom and Ypsomed.

Keywords: Type 1 Diabetes, Meal Management, Automated Insulin Delivery, Hybrid Closed-Loop System, Carbohydrate Counting, Youth and Young Adults