MON-147 Variation of Measured Values Associated with Different Lots of Sensors for the Freestyle Libre

The FreeStyle Libre Flash glucose monitoring system (Abbott Diabetes Care, Alameda, CA, USA) is a continuous glucose monitoring system that is used worldwide for improving plasma glucose control in patients with diabetes mellitus. It has numerous benefits, which include enabling the measurement of interstitial glucose levels anywhere and at any time without collecting blood samples, and it does not require calibration(1, 2).The corresponding author, who has impaired glucose tolerance, on the basis of 75-g oral glucose tolerance test, extensively uses the FreeStyle Libre glucose monitoring system since February 2017. Although we have used six different lots of the sensors so far, we recently and unexpectedly noted that one of the sensors for the FreeStyle Libre system showed completely different measured values. Herein, we designated these six lots as lot A through F. We observed that 53.4% and 54.6% of repeatedly measured interstitial glucose levels by Lot A were below 80 mg/dL (We tested two of Lot A on different day to confirm reproducibility.). On the other hand, the rest of 5 Lots (Lot B through F) showed that 0% of repeatedly measured interstitial glucose levels was below 80 mg/dL. However, unexpectedly, self-monitoring of blood glucose (SMBG) using a FS precision electrode with using the same reader of FreeStyle Libre system measured completely different values. Thus, Lot A consistently showed lower measured values compared to with those obtained using SMBG. As measured values using the FreeStyle Libre system are considered to be accurate as well as those obtained by SMBG, we decided to simultaneously test different lots of sensors, although the arm-attached sensor for B was on a different side than that for lot A. Lot A consistently showed measured values that were 20-30 mg/dL lower than those of Lot B. All of the sensors for the FreeStyle Libre system used in this study were kept in our office. The room temperature was kept at 25+/-2 (0)C and the humidity was around 40%. Our city is above sea 100mL.It is obvious that one of the six different lots showed inappropriately lower measured values and these discrepancies were critical. Therefore, it is possible that some lots of sensors for the FreeStyle Libre system do not work correctly, and may lead to false readings of hypoglycemia and a delayed response to true hyperglycemia, which requires a rapid response. In summary, when changing of the lots of sensors for the FreeStyle Libre glucose monitoring system, we recommended that patients double check measured values using an alternative method, such as SMBG, as soon as possible to avoid incorrect blood glucose control.