Continuous glucose monitoring (CGM) provides up to 288 blood glucose levels per day, updated every 5 minutes and displayed in real-time on the insulin pump, which can be used to enhance delivery of insulin through pump therapy. In addition this real-time CGM data includes "trend arrows" which indicate when the blood glucose is rapidly falling or rising thus enabling the pump user to make immediate adjustments in insulin delivery to prevent subsequent low or high blood sugars. The trend arrows are displayed when the blood glucose is rapidly falling or rising. For example, if the glucose is increasing by 1-2 mmol/L over 20 minutes, a single upward arrow alerts the pump wearer, who can then decide to give a bolus of insulin or increase the meal bolus. Should the glucose level be increasing at a rate greater than 2mmol/L over 20 minutes, 2 upward arrows are displayed and the user could decide to give a larger bolus. The purpose of the bolus adjustment is to add insulin for the predicted rise in glucose to prevent or reduce subsequent hyperglycemia. Similarly, a decrease in the insulin bolus is advised if glucose levels are falling as evidenced by one or two downward arrows.

However, effective strategies for adjusting insulin boluses based on CGM trend arrows are lacking. The JDRF CGM Study Group recommended that boluses be adjusted based on trend arrows using a standard 10-20% increase/decrease of the total original recommended bolus dose (10% for one arrow up or down, and 20% for two arrows up or down), with the original bolus dose calculated by the pump calculator (i.e. Bolus Wizard). However, the original recommended bolus dose is dependent on the amount of food to be consumed (grams of carbohydrate) and the current blood glucose (if above or below target range), as well as the amount of active insulin, and therefore increasing or decreasing the total recommended bolus by 10-20% may overcompensate for the trend arrows and result in postprandial hypoglycemia. Attempts to use the10/20% formula within CHEO's large pediatric pump/CGM population resulted in low acceptance and adherence by CGM users.

The CGM TIME Trial Study Group develop an innovative tool for adjusting boluses for CGM trend arrows based on the patient's own insulin sensitivity factor (ISF). The Trend Arrow Adjustment Tool formula is: if CGM shows a single arrow up or down: adjust bolus by +/- (1.5/ISF) and for 2 arrows up or down +/- (3/ISF). Use of the Trend Arrow Adjustment Tool within the CGM TIME Trial appears to lead to more appropriate adjustment in bolus dosing, and more effective prevention of subsequent hyper- and hypoglycemia. Furthermore, this tool appears to have excellent uptake amongst the TIME Trial participants, with observations that there is continued usage of the tool throughout the 12 month study, and greater satisfaction with this component of CGM. However, the tool has not been systematically evaluated.

The proposed study will evaluate the Trend Arrow Adjustment Tool, to determine its effectiveness in reducing postprandial hyper- and hypoglycemia, as well as parent, child/youth satisfaction, and ease of use of the tool based on self-report measures. Comparison will be made with the 10/20% bolus adjustment & also to no adjustments to meal boluses (i.e. ignoring CGM trend arrows). Should use of the Trend Arrow Adjustment Tool lead to more time spent within the target glucose range, this will have immediate clinical benefit for patients, including improved quality of life, and potentially a reduction in HbA1c and prevention of long-term complications.

Detailed protocol:

Phase 1(inpatient evaluation):

This part of the study will take place in a standardized outpatient setting (CHEO Medical Day Unit/Clinic). The CGM trend arrows will be stimulated using two typical clinical scenarios: oral fast acting carbohydrate (to stimulate upward trend arrows) and exercise (to stimulate downward trend arrows).

40 participants will be enrolled in this phase of the study (20 of whom will have oral fast acting carbohydrate and 20 of whom will engage in exercise). Once trend arrows have been triggered, the subjects will receive a standardized meal, and an adjusted insulin bolus. Comparison will be made between the Trend Arrow Adjustment Tool (based on the patient's own insulin sensitivity factor) and the standard bolus adjustment recommendations (i.e. +/- 10/20%, based on the STAR 1 Trial and JDRF CGM Study Group). Phase 1 of the study will lead directly to Phase 2's outpatient evaluation.

Upward CGM trend arrows (Group 1):

1. Participants will arrive fasting at the outpatient clinic. They will have been asked to change their pump and CGM the morning of the previous day and to ensure that both are functioning well prior to arrival. An iPro2 (blinded) continuous glucose monitor will be inserted subcutaneously, to provide a second recording of glucose trends. Each subject will be randomized, in a 1:1 ratio, to either the Trend Arrow Adjustment Tool (based on the patient's own insulin sensitivity factor) or the standard bolus adjustment recommendations (i.e. +/- 10/20%, based on the STAR 1 Trial and JDRF CGM Study Group).
2. Baseline blood glucose will be checked using a validated blood glucose meter, via capillary sampling.
3. At study onset, target blood glucose is 3.6-11mmol/L. If CGM shows trend arrows, the participant will proceed directly to a meal. If there are no upward trend arrows, a preliminary dose of Glucodex (oral fast acting carbohydrate) will be given. The participant will wait for up to one hour or until CGM ↑↑ are triggered, and will then proceed to a meal.
4. The participant will be given a standardized meal (containing a fixed amount of carbohydrate, fat and protein, appropriate for subject's weight) and a bolus of insulin will be given, via the insulin pump, using either the Trend Arrow Adjustment Tool or the standard 10/20% formula, to adjust the bolus dosage recommended by the bolus wizard.
5. Glucose levels will be monitored using hourly capillary blood samples, CGM and iPro2. Glucose levels \

Inclusion Criteria:

1. Participants will be children and youth aged 5-18 years, attending CHEO diabetes clinic
2. Established Type 1 diabetes for more than 1 year,
3. Who have used an insulin pump and CGM for at least 3 months.
4. Willing to wear iPro2 blinded CGM and to use the Trend Arrow Adjustment Tool and the 10/20% bolus adjustment method.
5. Internet access at home (to upload CGM data).

Exclusion Criteria:

1. Conditions which may interfere with the subject's ability to participate in the study.
2. Has received oral and/or intravenous steroid therapy (for any indication, at any dose and/or for any duration) on more than 2 separate occasions in the past 12 months. Use of inhaled and/or topical steroid therapy in the last 12 months does not exclude the subject