The FreeStyle Libre® (Abbott Laboratories) is a flash glucose monitoring system (FGMS) that measures interstitial glucose (IG) and stores this data onboard until scanned by the reader. The sensors are factory-calibrated, and the system is user-friendly, inexpensive, and could be extremely useful for monitoring diabetes but has not yet been validated for use in cats. We compared blood glucose (BG) concentrations (measured by AlphaTRAK) to IG (measured by the FreeStyle Libre®), during 16 IV glucose tolerance tests (IVGTT) in seven purpose-bred laboratory cats, across the eu- and hyper-glycemic range (184 samples). Correlation between BG and IG was assessed using Pearson’s r and the accuracy was assessed against BG as the reference standard using the Bland-Altman method. In the immediate 30 minutes following intravenous bolus of glucose when BG concentrations were declining rapidly (@ 2%/min), IG increased slowly, resulting in a difference of as much as 32.2 mmol/L (579 mg/dL), and no positive correlation between BG and IG. At baseline and between minutes 45–180 of the IVGTT, when BG was stable or rate of decline slow (@ 0.5%/min), there was a strong positive correlation between BG and IG (r=0.97 [95% CI=0.96–0.98]) with a consistent bias (across the BG range) towards underestimating BG by the Libre (mean±SD bias 1.3±1.0 mmol/L [23.3±18.1 mg/ml]). In conclusion, the FreeStyle Libre® may be appropriate to monitor diabetic cats, but consideration should be made for the lag between IG and BG during periods of rapid change.

Disclosures

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