A Clinical Trial of the Accuracy and Treatment Experience of the Flash Glucose Monitor FreeStyle Libre in Adults with Type 1 Diabetes

Arndís F. Ólafsdóttir, Stig Attvall, Ulrika Sandgren, Sofia Dahlqvist, Aldina Pivodic, Stanko Skrtic, Elvar Theodorsson, Marcus Lind

In Sweden, FreeStyle Libre a flash glucose monitoring system came onto the market in 2014 as a complement to self-monitoring of blood glucose. The aim of this study was to evaluate the accuracy and treatment experience of the FreeStyle Libre system. Fifty-eight adults with type 1 diabetes used FreeStyle Libre for 10-14 days and measured capillary blood glucose levels with the HemoCue blood glucose measurement system at least six times a day simultaneously. For the entire study period, the mean absolute relative difference (MARD) was 13.2% (95% confidence interval [CI] 12.0%-14.4%). MARD was 13.6% (95% CI 12.1%-15.4%) during week 1 and 12.7% (95% CI 11.5%-13.9%) during week 2. The mean absolute difference (MAD) for the whole study period was 19.8 mg/dL (1.1 mmol/L) (95% CI 17.8-21.8 mg/dL), including 20.5 mg/dL (1.14 mmol/L) during week 1 and 19.0 mg/dL (1.05 mmol/L) during week 2. The overall correlation coefficient was 0.96. For glucose values <72, 72-180, and >180 mg/dL (<4, 4-10, and >10 mmol/L), the MARD was 20.3% (95% CI 17.7%-23.1%), 14.7% (95% CI 13.4%-16%), and 9.6% (95% CI 8.5%-10.8%), respectively, and respective MAD values were 12.3, 17.8, and 23.6 mg/dL (0.69, 0.99, and 1.31 mmol/L). Using the 10-item visual analog scale, patients rated their experience with FreeStyle Libre as generally positive, with mean values ranging from 8.22 to 9.8. FreeStyle Libre had a similar overall MARD as continuous blood glucose monitoring systems in earlier studies when studied in similar at-home conditions. The overall patient satisfaction was high.