Accuracy of a Flash Glucose Monitoring System in Diabetic Dogs

Abstract

Background: A novel flash glucose monitoring system (FGMS) (FreeStyle Libre, Abbott, UK) was recently developed for humans. It continuously measures the interstitial glucose (IG) concentrations for 14 days.

Objectives: To assess the clinical and analytical accuracy of the FGMS in diabetic dogs.

Animals: Ten client-owned diabetic dogs on insulin treatment.

Methods: Prospective and observational study. The FGMS was placed on the neck for up to 14 days. During the 1st-2nd, 6-7th, and 13-14th days from application, the IG measurements were compared with the plasma (EDTA) glucose (PG) concentrations analyzed by a reference hexokinase based method.

Results: The application and the use of the FGMS were apparently painless, easy, and well tolerated by all dogs. Mild erythema at the site of the application was found in 5/10 dogs at the end of the wearing period. A good correlation between IG and PG concentrations (rho = 0.94; P < .001) was found. The FGMS was 93, 99, and 99% accurate at low, normal, and high blood glucose concentrations. Mean ± standard deviation difference from the reference method was 2.3 ± 46.8 mg/dL.

Conclusion and clinical importance: The FGMS is easy to use and is accurate for IG glucose measurement in diabetic dogs.

Keywords: Canine; Diabetes mellitus; FreeStyle Libre; Noninvasive glucose measurement.

Figure 1

FreeStyle Libre FGMS is composed of the following: (A) the reader that in one‐second shows the glucose reading; (B) the sensor that with a small catheter measures the interstitial blood glucose in the subcutaneous tissue; and (C) the sensor is applied on the skin by the provided applicator.

Figure 2

(A) The sensor is applied on the neck of the dog; (B) with extra‐tape to secure it on the skin surface; and (C) a bandage was used as an additional security.

Figure 3

Bland–Altman plots represent the differences between blood glucose concentrations obtained by the use of FGMS versus the reference method (hexokinase). (A) the values obtained by the use of FGMS and the PBGM (Accu‐Check Aviva Nano); and (B) including all samples for ISO15197: 2013. On the x‐axis are, the reference glucose values plotted against the absolute errors for each corresponding value. The standard required limits defined by the gray symmetric lines: at ±15 mg/dL from the reference value for glucose determinations <100 mg/dL and at ±15% from the reference for glucose ≥100 mg/dL. Percentages express the number of samples within limits when reference was < or ≥100 mg/dL and for the total number of measurements (central% value).

Figure 4

Parkes Consensus error grid analysis for the values obtained by FGMS and the representation with the percentage of values within A+B zones. The reference glucose values on the x‐axis are plotted against the blood glucose by the glucose meter (y‐axis). The different zones designate the magnitude of risk derived from the determination: no effect on clinical action (zone A), altered clinical action: little or no effect on clinical outcome (zone B), altered clinical action: likely to affect clinical outcome (zone C), altered clinical action: could have significant medical risk (zone D), and altered clinical action could have dangerous consequences (zone E) (Parkes et al,14).