Real-World Flash Glucose Monitoring Patterns in Portugal: The Association between Self-Monitoring Frequency and Measures of Glycemic Control

Introduction: Using a multinational database of de-identified FreeStyle Libre sensor readings, we analysed the subgroup of data for Portugal with the aim of understanding the daily scanning behaviour for FreeStyle Libre users in Portugal and the association with performance against internationally agreed measures of glycaemic control. Methods: De-identified data from FreeStyle Libre readers was collected between September 2014 and December 2020. Data for Portugal was extracted and analysed to determine the relationship between glucose scanning frequency and accepted measures of glycaemic control, including: estimated HbA1c, time in range 70-180 mg/dL, time with glucose <70 mg/dL, time with glucose <54 mg/dL, and time with glucose >180 mg/dL. Results: The Portugal dataset included 13 323 readers representing 171 million individual glucose readings. Users were rank-ordered by daily scan rate and separated into 10 equal-sized bins groups, ranging from the lowest (mean scan rate of 3.70 scans/day) to highest (mean scan rate of 35.77 scans/day). Users in Portugal performed an average of 13.2 daily glucose scans (median 10.7, IQR 6.6-16.4). Estimated HbA1c decreased from 8.59% to 7.26% as scan rates increased from lowest to highest (p < 0.05). Time in range 70-180 mg/dL improved from 44.51% to 61.31% with increasing scan rates (p < 0.05) and time with glucose >180 mg/dL fell from 50.18% to 33.80% (p < 0.05). Time with glucose <54 mg/dL fell from a median of 1.28% to 0.52% as mean daily scans increased from 8.14 to 35.77 (p < 0.05). Conclusion: Our study shows that, under real-life conditions, flash glucose monitoring enables users in Portugal to regularly monitor their glucose, and higher frequencies of monitoring are associated with improvements in accepted measures of glucose control, including lower estimated HbA1c and increased time in range, as well as less time in hyperglycaemia and clinically significant hypoglycaemia. These results are aligned with those observed world-wide.