Memorandum

Endocrine Society releases insulin dose adjustment guidelines for FreeStyle Libre CGM trend arrows – November 16, 2018

Based on correction factor and observed trend, similar to Dexcom G5 paper; Additional guidelines provided for scanning time and frequency (Endocrine Society article)

The Endocrine Society announced new guidelines for adult FreeStyle Libre users to leverage trend arrows for insulin dose adjustments. The recommendations, published in the Journal of the Endocrine Society, expand on the Society’s similar methods for Dexcom G5 users provided last year (adults and pediatrics). Both give specific changes in insulin doses in absolute units based on the trend arrow and a patient’s correction factor (CF). The lower the sensitivity to insulin, the greater the recommended dose adjustment for a given trend arrow. As the authors noted, guidelines were modified slightly to accommodate FreeStyle Libre’s different display icon for a very rapid change in glucose (a single arrow is used, rather than Dexcom’s double arrows). Since FreeStyle Libre is only approved for ≥18 year-olds in the US, the guidelines focus on adult use only.

The Society’s guidelines also offer suggestions for scanning time and frequency. For example, the authors advise hourly scanning for up to four hours following a correction action for hyperglycemia, and suggest scanning every 15 minutes until a steady target glucose is achieved following hypoglycemia. Additional scanning and dosing guidelines are provided for specific situations, including after a meal and before physical activity (see below), and when the patient is ill. More conservative recommendations are given for elderly or frail adults. The work was supported by an unrestricted educational grant to the Endocrine Society from Abbott Diabetes.

We applaud the Society’s approach: eliminating the complicated percentage math of previous techniques, while still allowing for an adequate degree of customization. Over time, we fully expect these guidelines to directly feed into CGM-based bolus calculators that account for trends – a far more automated way to implement these guidelines. For now, the utility of these guidelines fully rests on HCP and patient education.

One question is whether CGM trend arrows will standardize over time between systems. With the Dexcom and now Abbott guidelines, it seems these are staying device-specific.

Insulin Dose Adjustments in Adults: Pre-Meal and Corrections ≥4 Hours Post-Meal

Pre-Exercise Planning

Post-Meal Scanning and Treatment Decisions

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--by Maeve Serino, Adam Brown, and Kelly Close