Background: Continuous glucose monitoring (CGM) measures interstitial glucose and displays trend arrows, showing the direction and rate of change in glucose. Trend arrows allow the child/youth to take action to prevent hyper- and hypoglycaemia. Effective strategies for adjusting insulin for trend arrows are lacking. The JDRF CGM Study Group recommended a 1020% increase/decrease in the insulin dose. However, the bolus dose is dependent on amount of food to be consumed and current blood glucose, which could potentially lead to overcorrection if pre-prandial glucose is elevated and/or if eating high carbohydrate meals. In addition, the formula requires the pump user to perform mathematical calculations with each arrow, limiting the tools uptake in paediatrics. We developed an alternative tool, based on the patients insulin sensitivity factor.
Objective and hypotheses: To compare the effect of the Trend Arrow Adjustment Tool, the 10/20% adjustment, and no adjustment for arrows; on postprandial glucose. To evaluate patient satisfaction, ease and frequency of use of both adjustment methods.
Method: A single-blinded, counterbalance, treatment assignment crossover study, of 20 subjects with type 1 diabetes. During a hospital assessment, trend arrows were induced through exercise or oral carbohydrate. Subjects consumed a meal with the insulin adjusted for trend arrows using the assigned method. Subjects used the assigned method during week 1; made no adjustment for arrows in week 2, and used the alternative method in week 3. CGM data was used to analyse postprandial glucose.
Results: Time with postprandial glucose in target range was equivalent with Trend Arrow Adjustment Tool© and the 10/20% adjustment. There was a trend towards more time in target range and less hypoglycaemia, with use of either tool compared to ignoring arrows. Significantly more errors were made with the 10/20% adjustment. Satisfaction and ease of tool use was greatest with Trend Arrow Adjustment Tool©.
Conclusion: The Trend Arrow Adjustment Tool© is a simple and well received method of adjusting insulin boluses for CGM trend arrows, which can be successfully used in the paediatric population.
Funding: This work was supported by grants to M.L. from JDRF Canadian Clinical Trial Network (CCTN; JDRF Grant #80-2010-585). CCTN is a public-private partnership including JDRF International, JDRF-Canada and the Federal Economic Development Agency for Southern Ontario. E.H. received support from a CCTN Postdoctoral Fellowship Grant.
01 Oct 2015 - 03 Oct 2015