The FreeStyle Libre 2 system demonstrates limited analytical accuracy without resulting in detrimental clinical decisions.

Abstract

Objective: To evaluate the performance of a second-generation flash glucose monitoring system (FGMS; FreeStyle Libre 2) in nondiabetic dogs during rapidly induced hypoglycemia.

Methods: In a prospective, observational study, regular insulin was administered to 23 healthy dogs to induce hypoglycemia, with subsequent correction. Serial measurements of interstitial glucose with FGMS and blood glucose (BG) with a portable BG monitor (PBGM) were recorded every 10 minutes for 90 minutes. At each time point, blood was also collected for gold standard BG measurement via clinical chemistry analyzer. Analytical and clinical accuracy was determined by fulfillment of International Organization for Standardization 15197:2013 criteria.

Results: For BG values < 100 mg/dL, 67.2% of PBGM measurements and 50.9% of FGMS measurements were within ± 15 mg/dL of the reference method. In Parkes error grid analysis, 94.9% of PBGM and 88.6% of FGMS measurements fell within zones A and B. Readings within higher-risk zones were rare, with no PBGM values and 0.6% of FGMS values in zone D and neither producing readings in zone E.

Conclusions: In this model of rapidly induced hypoglycemia, the FGMS demonstrated limited analytical accuracy compared to the reference standard. However, it rarely produced glucose readings likely to lead to detrimental clinical decisions.

Clinical relevance: The FreeStyle Libre 2 is clinically useful for monitoring glucose trends in dogs, though results should be interpreted with caution during periods of rapid glycemic change.