Difference in the accuracy of the third-generation algorithm and the first-generation algorithm of FreeStyle Libre continuous glucose monitoring device.

Background: FreeStyle Libre uses the algorithm to calculate the sensor glucose (SG) levels. The manufacturer announced that they had changed the algorithm from the first generation (Gen. 1) to the third generation (Gen. 3). To assess the difference, we conducted an observational study to analyze the characteristics of the measurements by these two algorithms compared to the capillary blood glucose (BG) levels.

Methods: Participants with type 1 diabetes wore two FreeStyle Libre sensors, one on the left arm used with Gen. 3 algorithm, and another on the right arm used in combination with the FreeStyle Libre Reader with Gen. 1 algorithm.

Results: Data were collected from 11 participants. The Bland-Altman analysis of the measurements by Gen. 3 algorithm showed bias of 7.4 mg/dl and no proportional bias was observed (r=0.130). In contrast, the Bland-Altman analysis of the measurements by Gen. 1 algorithm showed bias of 4.4 mg/dl and proportional bias was observed (r=0.424). The MARD of Gen. 3 algorithm and Gen. 1 algorithm was 11.9±9.0% and 9.7±8.3%, respectively (P=0.053).

Conclusion: No proportional bias in the measurements by Gen. 3 algorithm was observed, but in those by Gen. 1 algorithm. J. Med. Invest. 71 : 225-231, August, 2024.