medwireNews: Study results suggest that the accuracy of the FreeStyle Libre 14-day flash glucose monitoring system is adequate for patients with type 1 diabetes during its entire lifetime, although it tends to be less so during the beginning and end of its use.
Nonetheless, the Canadian researchers stress that its accuracy in the first 48 hours remained comparable to that of the Dexacom G5 glucose sensor, which was the first continuous glucose monitoring system approved by the US FDA that allowed treatment decisions without finger-prick tests.
Fourteen trial participants with type 1 diabetes spent two or three 24-hour periods at a research facility – separated by a median of 2 weeks – wearing the FreeStyle Libre system.
Information was collected from 36 of these devices in total, with eight participants visiting the facility three times and six attending twice. Eighteen of the devices were aged between 0 and 1 day, nine were aged 5 to 7 days, and another nine were aged between 13 and 14 days.
Participants also wore a Dexcom G5 glucose sensor aged 1–2 days for 24 to 48 hours before the visits that was calibrated at least every 12 hours using the person’s regular capillary glucose meter, with each individual wearing both sensors simultaneously.
Ahmad Haidar (McGill University, Montreal) and colleagues then assessed the FreeStyle Libre accuracy using the mean absolute relative difference (MARD) between the sensor values and plasma glucose measurements taken every 10 to 30 minutes from venous blood samples.
Results from 1930 pairs of sensor and plasma glucose measurements revealed that the mean and median MARD were significantly greater for FreeStyle Libre sensors aged 0–1 days, at a corresponding 14.5% and 11.2%, than for those aged 5–7 days, at 7.8% and 6.6%.
Mean and median MARD for sensors aged 13–14 days were 14.7% and 11.2%, respectively, which were numerically higher than the values observed with sensors aged 5–7 days, but not significantly so.
The researchers report that for FreeStyle Libre sensors aged 0–1 days, 1.9% of points fell in the potentially dangerous zones on Clarke’s error grid analysis, compared with 0.2% for those aged 5–7 days and 0.4% for sensors aged 13–14 days.
Mean MARD was similar with the FreeStyle Libre and Dexcom G5 sensors, at 12.8% and 12.5%, respectively.
Reporting in Diabetes Technology and Therapeutics, the researchers conclude: “We found that the accuracy of FreeStyle Libre is adequate throughout its lifetime but is least accurate during its first and last days. Its accuracy was comparable with Dexcom G5 sensors when both were aged 1–2 days.”
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