The Influence of Skin Thickness on Flash Glucose Monitoring System Accuracy in Dogs with Diabetes Mellitus

Abstract

A flash glucose monitoring system (FGMS) has been validated for use in diabetic dogs. However, it is unknown whether skin thickness affects FGMS measurements. The aim of this study was to evaluate whether FGMS accuracy is affected by skin thickness. Fourteen client-owned diabetic dogs on insulin treatment were prospectively enrolled in the study. The dogs were divided into two groups according to their ultrasound-measured skin thickness: dogs with skin thickness < 5 mm (Group 1) and dogs with skin thickness > 5 mm (Group 2). On days 1, 7 and 14, glucose curves were obtained simultaneously using the FGMS and a validated portable blood glucose meter. Paired measurements were used to calculate the mean bias and to determine accuracy according to ISO 15197:2013 criteria. The mean bias was significantly inversely correlated (p = 0.02; r = −0.6) with the mean skin thickness. Clinical accuracy was observed only in Group 2, with 99% of the results in zone A + B of the Parkes consensus error grid analysis. In conclusion, skin thickness seems to affect FGMS measurements, and the device is accurate in dogs with thicker skin (>5 mm); in dogs with thin skin (<5 mm), the clinical accuracy is low, and the results should be interpreted with caution.

Evaluation of the FreeStyle Libre, a flash glucose monitoring system, in client-owned cats with diabetes mellitus

“…Based on capillary BG measurements, samples were classified as hypoglycaemic (<3.9 mmol/l), normoglycaemic (3.9–10.0 mmol/l) or hyperglycaemic (>10.0 mmol/l). 41 …”

“…The sensor is suitable for up to 14 days of use. 6 , 20 , 22 , 33 – 35 To date, only a few studies have been published regarding the use of the FreeStyle Libre in dogs and cats, 13 , 33 – 41 with only four of them specifically in cats. 13 , 35 , 37 , 40 …”

Clinical utility of serum fructosamine in long‐term monitoring of diabetes mellitus in dogs

“…The most commonly used additional glycaemic control monitoring tools in diabetic dogs include HbA1c and FGMS. However, both have certain shortcomings, possibly limiting their utility as sole monitoring markers 3,15,22 . HbA1c allows assessment of glycaemic control during the preceding 2–3 months, but might be less suitable when frequent therapeutic changes are being made 3 .…”

“…Moreover, when the diagnostic accuracy of sFA and HbA1c for differentiating good glycaemic control from moderate or poor control (determined by CS and BG curve data) is compared, the latter shows no advantage over sFA 3 . FGMS provides elaborate data on daily responses to insulin, 24 but several technical limitations might potentially lead to inaccurate readings, and prolonged use might be cost‐prohibitive compared to sFA 15,22 . Furthermore, inaccuracies of FGMS in dogs with thin skin and in dogs with hypoglycaemia do occur, somewhat limiting the overall reliability of FGMS‐generated data 15,22,25 .…”

“…However, both have certain shortcomings, possibly limiting their utility as sole monitoring markers. 3,15,22 HbA1c allows assessment of glycaemic control during the preceding 2-3 months, but might be less suitable when frequent therapeutic changes are being made. 3 HbA1c is also affected by concurrent anaemia, increased erythrocyte turnover, hyperlipidaemia and hyperbilirubinaemia.…”