In a study published in Diabetes Technology & Therapeutics, which evaluated the performance and usability of the FreeStyle Libre Flash glucose monitoring system, interstitial glucose measurements with the FreeStyle Libre system were found to be accurate compared with capillary BG reference values. Accuracy remained stable over 14 days of wear and unaffected by patient characteristics.

72 patients with type 1 or type 2 diabetes were enrolled for this study. A sensor was inserted on the back of each upper arm for up to 14 days. Sensor glucose measurements were compared with capillary blood glucose (BG) results (approximately eight per day) obtained using the BG meter built into the reader (BG reference) and with the YSI analyzer (Yellow Springs Instrument, Yellow Springs, OH) reference tests at three clinic visits (32 samples per visit). Sensor readings were masked to the participants.

The accuracy of the results was demonstrated against capillary BG reference values, with 86.7% of sensor results within Consensus Error Grid Zone A. The percentage of readings within Consensus Error Grid Zone A on Days 2, 7, and 14 was 88.4%, 89.2%, and 85.2%, respectively. The overall MARD was 11.4% for sensor results with capillary BG reference. The overall MARD in the clinic alone for sensors' results with capillary BG reference and with YSI reference was 12.1% and 12%, respectively. 

The System is unique among existing interstitial glucose monitoring technologies in that the wired enzyme factory-only calibrated sensor has wear time of up to 14 days without additional calibration. This lack of reliance on an external BG monitor for calibration is a potential advantage as errors in BG meters could potentially lead to glucose monitoring system errors. 

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