This study aims to assess the safety and efficacy of a novel advanced bolus calculator in subjects with Type 1 diabetes. Insulin bolus calculators have been developed to aid insulin dose adjustment and existing standard insulin bolus calculator consist of a simple algorithm that requires five subject-specific parameters as input to generate a recommended bolus insulin dose:

• current blood glucose (mmol/L)
• target blood glucose (mmol/L)
• insulin-to-carbohydrate ratio (grams of carbohydrate per 1 unit of insulin)
• total grams of carbohydrate in meals
• insulin sensitivity factor (reduction in glucose per 1 unit of insulin)

The Diabetes Technology team at Imperial College have developed a novel advanced bolus calculator. The complete integrated system consists of a commercially available smartphone that holds the novel advanced algorithm. The system requires regular updates of cases derived from retrospective blinded continuous glucose monitoring data and for this a commercially available glucose sensor will be used. Each new case includes information about the problem (e.g. capillary blood glucose, meal information and physical exercise), solution (recommended insulin dose) and outcome (blood glucose following a meal). The novel decision support algorithm is based on case-based reasoning (CBR). CBR is an artificial intelligence technique that tries to solve newly encountered problems by applying the solutions learned from solved problems encountered in the past.

The end-product is therefore a subject specific insulin bolus calculator that continues to improve with time. The project utilises commercially available glucose sensors and smartphones (iPhone), integrated with a novel algorithm for insulin bolus calculation. The aim of the ABC4D is to minimise high and low glucose excursions which are associated with the complications of diabetes including blindness, kidney failure, nerve damage and cardiovascular disease.

An interim analysis was conducted in Phase 4 after 25 participants completed the study (in line with the protocol) and it was agreed to stop the study at this stage. A further protocol amendment was approved by REC/MHRA to commence ABC4D phase 5 (different CT.gov number: NCT03963219).

Inclusion Criteria:

• Adults ≥18 years of age
• Diagnosis of T1DM for > 1 year
• On MDI using a basal-bolus insulin regime
• Structured education in previous 3 years
• HbA1c ≤ 86mmol/mol
• No severe hypoglycaemia (defined as needing 3rd party assistance) in previous year

Exclusion Criteria:

• Recurrent severe hypoglycaemia
• Pregnant or planning pregnancy
• Breastfeeding
• Enrolled in other clinical trials
• Have active malignancy or under investigation for malignancy
• Addison's Disease
• Gastroparesis
• Autonomic neuropathy
• Concomitant use of GLP-1 analogues and gliptins
• Visual impairment
• Reduced manual dexterity

This was not part of the approved protocol. Any peer-reviewed publications will be shared with the study participants and will be accessible to other researchers.

6 months