Evaluation of the Disposable Sensor 5 (DS5) continuous glucose monitoring (CGM) device performance over a fifteen-day wear period

This is a single-arm pilot study with both controlled (in-clinic hypo- and hyperglycaemic inductions) and free-living conditions, in 28 participants with Type 1 diabetes. Participants will wear between 2 to 4 blinded Disposable Sensor 5 (DS5) continuous glucose monitoring (CGM) devices on their upper arm over the course of 15 days. These sensors will not be replaced at any point during the 15-day period. During this period, participants will undergo both a hypoglycaemia induction (by subcutaneous insulin bolus; target blood glucose level is 3.0 mmol/L) and a hyperglycaemia induction (by ingestion of a carbohydrate-rich meal with no insulin meal bolusing; target blood glucose level greater than or equal to 13.9 mmol/L). The carbohydrate-rich meal for the hyperglycaemia induction will depend on the participant's insulin-carb ratio, to be able to raise the person's blood glucose from euglycaermia to greater than or equal to 13.9 mmol/L, and will be determined by the study nurse on the day of induction. These inductions will occur on any combination of the following study days: Day 1 (within 2 hours of sensor start) Day 1 (between 2 and 24 hours of sensor start) Day 2 Day 3 Day 4 Day 5 Day 8 Day 10 (post sensor start) The sequence of the inductions will be determined by the arrival blood glucose level on first induction: - <5.5 mmol/L will lead to a hypoglycaemic induction first OR - Greater or equal to 11.1 mmol/L will lead to a hyperglycaemic induction first OR - Greater or equal to 5.5 and <11.1 mmol/L, first induction will be assigned by the PI. The second induction will depend on which induction (hypo/hyper) has been performed in the first in-clinic induction day above. Allocation of the 28 participants to the 2 in-clinic days each, will result in four participants per induction per study day. During the inductions, sensor performance will be compared with venous blood glucose measurements (participants will have a cannula inserted to continuously draw blood), determined using the Yellow Springs Instrument (YSI) glucose analyser, the gold standard for blood glucose measurements in clinical trials. On all other study days, participants will be advised to routinely perform at least 6 finger-prick tests of their blood glucose levels to enable evaluating differences in sensor glucose during these time periods. Each participant will attend in-clinic between 3 and 4 times within the 15 days of study period, as follows: Day 1 = eligibility check, consent, familiarisation, sensors insertion (2 hours) Day 1 to Day 10: Randomised to first in-clinic induction day (6 hours) Day 1 to Day 10: 2nd in-clinic induction day (6 hours) Day 15 = sensor removal and study completion (1 hour) The following will be collected to assess the feasibility of the study protocol: recruitment rate (number of patients recruited, number approached, time frame of recruitment), retention (proportion of recruited sample completing the study), device failure rate (percent of devices failing within 15 days), proportion of readings falling outside the reportable range. Logs will be maintained outlining logistical difficulties encountered during the pilot phase and will be disseminated amongst the research group. Where possible, strategies to overcome/minimise the impact of these difficulties will be identified.