Evaluation of a flash glucose monitoring system in dogs with diabetic ketoacidosis

A dose titration protocol for once-daily insulin glargine 300 U/mL for the treatment of diabetes mellitus in dogs

BACKGROUND

In purpose-bred dogs, insulin glargine 300 U/mL (IGla300) has long duration of action, peakless time-action profile, and low potency, making it suitable for use as a basal insulin.

HYPOTHESIS

To evaluate IGla300 in client-owned diabetic dogs monitored using a flash glucose monitoring system (FGMS).

ANIMALS

Ninety-five client-owned diabetic dogs, newly diagnosed or previously treated with other insulin formulations, with or without concurrent diseases.

METHODS

Prospective multi-institutional study. Clinical signs and standardized assessment of FGMS data, using treatment and monitoring guidelines established a priori, guided dose adjustments and categorization into levels of glycemic control.

RESULTS

The initial IGla300 dose was 0.5 U/Kg q24h for newly diagnosed dogs and (median dose [range]) 0.8 U/Kg (0.2-2.5) q24h for all dogs. Glycemic control was classified as good or excellent in 87/95 (92%) dogs. The IGla300 was administered q24h (1.9 U/kg [0.2-5.2]) and q12h (1.9 U/kg/day [0.6-5.0]) in 56/95 (59%) and 39/95 (41%) dogs, respectively. Meal-time bolus injections were added in 5 dogs (0.5 U/kg/injection [0.3-1.0]). Clinical hypoglycemia occurred in 6/95 (6%) dogs. Dogs without concurrent diseases were more likely to receive IGla300 q24h than dogs with concurrent diseases (72% vs 50%, respectively; P = .04).

CONCLUSIONS AND CLINICAL IMPORTANCE

Insulin glargine 300 U/mL can be considered a suitable therapeutic option for once-daily administration in diabetic dogs. Clinicians should be aware of the low potency and wide dose range of IGla300. In some dogs, twice-daily administration with or without meal-time bolus injections may be necessary to achieve glycemic control. Monitoring with FGMS is essential for dose titration of IGla300.

A concept for human use of real-time and remote monitoring of diabetic subjects using intermittent scanned continuous glucose measurement

BACKGROUND

Flash glucose monitoring systems like the FreeStyle Libre (FSL) sensor have gained popularity for monitoring glucose levels in people with diabetes mellitus. This sensor can be paired with an off-label converted real-time continuous glucose monitor (c-rtCGM) plus an ad hoc computer/smartphone interface for remote real-time monitoring of diabetic subjects, allowing for trend analysis and alarm generation.

OBJECTIVES

This work evaluates the accuracy and agreement between the FSL sensor and the developed c-rtCGM system. As real-time monitoring is the main feature, the system's connectivity was assessed at 5-min intervals during the trials.

METHODS

One week of glucose data were collected from 16 type 1 diabetic rats using the FSL sensor and the c-rtCGM. Baseline blood samples were taken the first day before inducing type 1 diabetes with streptozotocin. Once confirmed diabetic rats, FSL and c-rtCGM, were implanted, and to improve data matching between the two monitoring devices, the c-rtCGM was calibrated to the FSL glucometer readings. A factorial design 2 × 3^3 and a second-order regression was used to find the base values of the linear model transformation of the raw data obtained from the sensor. Accuracy, agreement, and connectivity were assessed by median absolute relative difference (Median ARD), range averaging times, Parkes consensus error grid analysis (EGA), and Bland-Altman analysis with a non-parametric approach.

RESULTS

Compared to the FSL sensor, the c-rtCGM had an overall Median ARD of 6.58%, with 93.06% of results in zone A when calibration was not carried out. When calibration frequency changed from every 50 h to 1 h, the overall Median ARD improved from 6.68% to 2.41%, respectively. The connectivity evaluation showed that 95% of data was successfully received every 5 min by the computer interface.

CONCLUSIONS AND CLINICAL IMPORTANCE

The results demonstrate the feasibility and reliability of real-time and remote subjects with diabetes monitoring using the developed c-rtCGM system. Performing calibrations relative to the FSL readings increases the accuracy of the data displayed at the interface.

Assessment of the FreeStyle Libre 2 interstitial glucose monitor in hypo- and euglycemic cats

BACKGROUND

Continuous glucose monitoring systems have been validated for eu- and hyperglycemic cats. The FreeStyle Libre 2 (FSL2) is sufficiently accurate in people during hypoglycemia to guide critical treatment decisions without confirmation of blood glucose concentration (BG).

OBJECTIVES

Assess FSL2 accuracy in cats with hypoglycemia.

ANIMALS

Nine healthy, purpose-bred cats.

METHODS

Hyperinsulinemic-hypoglycemic clamps were performed by IV infusion of regular insulin (constant rate) and glucose (variable rate). Interstitial glucose concentration (IG), measured by FSL2, was compared to BG measured by AlphaTrak2. Data were analyzed for all paired measurements (n = 364) and separately during stable BG (≤1 mg/dL/min change over 10 minutes). Pearson's r test, Bland-Altman test, and Parkes Error Grid analysis respectively were used to determine correlation, bias, and clinical accuracy (P < .05 considered significant).

RESULTS

Overall, BG and IG correlated strongly (r = 0.83, P < .0001) in stable glycemia and moderately at all rates of change (r = 0.69, P < .0001). Interstitial glucose concentration underestimated BG in euglycemia, but the BG-IG difference was progressively smaller as BG decreased (12.9 ± 12.2, 8.8 ± 11.2, -3.2 ± 7.4, and -7.8 ± 5.2 mg/dL in the ranges of 80-120 [n = 64], 60-79 [n = 29], 50-59 [n = 71], and 29-49 mg/dL [n = 53], respectively).

CONCLUSIONS

Although IG underestimates BG throughout most of the hypo-euglycemic range, IG generally overestimates BG in marked hypoglycemia (<60 mg/dL). It is therefore imperative to evaluate FSL2 results in this critical range with caution.

Diabetes Ketoacidosis and Hyperosmolar Hyperglycemic Syndrome in Companion Animals

Diabetes mellitus is a common endocrinopathy in dogs and cats. Diabetes ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are life-threatening complications of diabetes resulting from an imbalance between insulin and the glucose counter-regulatory hormones. The first part of this review focuses on the pathophysiology of DKA and HHS, and rarer complications such as euglycemic DKA and hyperosmolar DKA. The second part of this review focuses on the diagnosis and treatment of these complications.

Successful multimodal treatment of extreme hypertriglyceridemia in a juvenile diabetic dog

OBJECTIVE

To describe the therapeutic protocol used to normalize severe hypertriglyceridemia in a dog.

CASE SUMMARY

A 7-month-old, 1.2-kg female Pomeranian presented with acute polyuria, polydipsia, and ocular discoloration. Diagnoses included diabetic ketosis, severe hypertriglyceridemia (>225 mmol/L [>20,000 mg/dl]), lipemia retinalis, and bilateral uveitis. The triglyceride concentration was near normal within 2 days of initiating treatment with fenofibrate, regular insulin constant rate infusion (CRI), manual therapeutic plasma exchange (TPE), and a low-fat diet. All clinical signs resolved. The dog has had no relapse of hypertriglyceridemia at the time of writing the manuscript, 6 months later, with continued treatment of diabetes mellitus.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first case report documenting the combination of fenofibrate, insulin CRI, and manual TPE for treatment of severe hyperlipidemia in a dog. Detailed protocols for manual TPE and a novel insulin CRI are provided. A discussion of multiple spurious biochemical and hematologic errors associated with the severe hypertriglyceridemia is also provided.

Continuous Glucose Monitoring in Dogs and Cats: Application of New Technology to an Old Problem

In recent years, glucose monitoring has been revolutionized by the development of continuous glucose monitoring systems (CGMS), which are wearable non/minimally invasive devices that measure glucose concentration almost continuously for several consecutive d/wk. The Abbott FreeStyle Libre is the CGMS used most commonly. It has adequate clinical accuracy both in dogs and cats, even though the accuracy is lower in the hypoglycemic range. It allows an accurate identification of glycemic excursions occurring throughout the day as well as of glucose variations during consecutive days, enabling the clinician to make a more informed decision about the insulin dose and frequency of administration.

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

BACKGROUND

Serum fructosamine (sFA) is used to assess glycaemic control in dogs with diabetes mellitus (DM). Nevertheless, its interpretation is hindered by several limitations.

METHODS

This retrospective study evaluates the long-term diagnostic performance of sFA for monitoring clinical control of DM. sFA, bodyweight, appetite, presence of polyuria/polydipsia and clinical scores (CS; well-controlled DM, CS-0; uncontrolled DM, CS-1) were recorded.

RESULTS

The study included 75 dogs (321 visits; median 3 visits/dog; range 1-19). Mean sFA was higher (p < 0.001) on visits with CS-1 (584 μmol/L; 95% confidence interval [95% CI] 561-608) than on visits with CS-0 (506 μmol/L; 95% CI 484-528). Increases in sFA increased   the odds ratio for CS-1 (1.37; 95% CI 1.24-1.52, p < 0.001). sFA was moderately predictive of the CS (area under receiver operating characteristic curve = 0.75; 95% CI 0.70-0.80; p < 0.0001), with a 486 μmol/L cutoff yielding 80% sensitivity and 59% specificity. Mean sFA was lower (p = 0.005) when hypoglycaemic episodes were suspected (496 μmol/L; 95% CI 450-541) than in their absence (572 μmol/L; 95% CI 548-596). sFA is moderately accurate for classifying CS in diabetic dogs. Decreasing sFA over follow-ups indicates improved CS but might suggest occurrence of hypoglycaemic episodes.

LIMITATIONS

Retrospective design, variable treatments and comorbidities are limitations of this study.

CONCLUSION

sFA has a moderate clinical utility in the long-term monitoring of diabetic dogs, but may serve as a first-line, accessible diagnostic tool. Discordant CS and sFA evaluation, or decreased sFA, warrants additional monitoring (i.e., continuous glucose monitoring).

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

Objectives

Home blood glucose monitoring using a portable blood glucose meter is important in the management of feline diabetes mellitus, but taking blood samples may be stressful for owners and cats. A flash glucose monitoring system measuring interstitial glucose, such as the FreeStyle Libre, overcomes some of these drawbacks. The aim of this study was to evaluate the practical use and analytical and clinical accuracy of the FreeStyle Libre in 41 client-owned diabetic cats.

Methods

In this prospective study, interstitial glucose concentrations were measured with the FreeStyle Libre and compared with blood glucose concentrations measured with a portable blood glucose meter (AlphaTRAK) on days 1, 7 or 8 and 14 after application of the device. Cat behaviour during application, location, skin reaction at the attachment site and owner satisfaction were assessed. Accuracy was determined by fulfilment of ISO 15197:2013 criteria, including Bland–Altman plotting and error grid analysis.

Results

Placing the device was easy, with 70% of cats showing no reaction. Most sensors were placed on the thoracic wall. Skin reactions at the attachment site were not present or mild in almost all cats. Owners were very satisfied with the use of the FreeStyle Libre. Median functional life of the sensor was 10 days (range 1–14). Good correlation was found between interstitial and blood glucose measurements (rho[r] = 0.88, P <0.0001). Fifty-three percent of interstitial glucose concentrations were within a maximum deviation of 15% from blood glucose concentrations and 92.7% were within the safe risk zones 0 and 1 of the surveillance error grid.

Conclusions and relevance

The flash glucose monitoring system was easy to use and owners of diabetic cats were satisfied with its use. Although the device did not completely fulfil ISO requirements, it is sufficiently accurate for glucose monitoring in diabetic cats.

Less is more? Ultra-low carbohydrate diet and working dogs' performance

New Zealand farm working dogs are supreme athletes that are crucial to agriculture in the region. The effects that low or high dietary carbohydrate (CHO) content might have on their interstitial glucose (IG) and activity during work are unknown. The goals of the study were to determine if the concentration of IG and delta-g (a measurement of activity) will be lower in dogs fed an ultra-low CHO high fat diet in comparison to dogs fed a high CHO low fat diet, and to determine if low concentrations of IG are followed by reduced physical activity. We hypothesized that feeding working farm dogs an ultra-low CHO diet would reduce their IG concentrations which in turn would reduce physical activity during work. We prospectively recruited 22 farm dogs from four farms. At each farm, dogs were randomized to one of two diets and had a month of dietary acclimation to their allocated diet. The macronutrient proportions as a percentage of metabolizable energy (%ME) for the high CHO low fat diet (Diet 1) were 23% protein, 25% fat, and 52% CHO, and for the ultra-low CHO high fat diet (Diet 2) 37% protein, 63% fat, and 1% CHO. Following the acclimation period, we continuously monitored IG concentrations with flash glucose monitoring devices, and delta-g using triaxial accelerometers for 96 h. Dogs fed Diet 2 had a lower area under the curve (±SE) for IG (AUC _{Diet 2} = 497 ± 4 mmol/L/96h, AUC _{Diet 1} = 590 ± 3 mmol/L/96h; P = 0.002) but a higher area under the curve (±SE) for delta-g (AUC _{Diet 2} = 104,122 ± 6,045 delta-g/96h, AUC _{Diet 1} = 80,904 ± 4,950 delta-g/96h; P< 0.001). Interstitial glucose concentrations increased as the activity level increased (P < 0.001) and were lower for Diet 2 within each activity level (P < 0.001). The overall incidence of low IG readings (< 3.5 mmol/L) was 119/3810 (3.12%), of which 110 (92.4%) readings occurred in the Diet 2 group (P = 0.001). In the Diet 2 group, 99/110 (90%) of the low IG events occurred during the resting period (19:00–06:00). We conclude that feeding Diet 2 (ultra-low CHO high fat diet) to working farm dogs was associated with increased delta-g despite decreased IG concentrations. Interstitial glucose concentrations were positively associated with dogs’ activity levels independent of diet. Lastly, events of low IG occurred at a low incidence and were predominantly seen between 19:00–06:00 in dogs fed the ultra-low CHO high fat diet.

Validation of a flash glucose monitoring system in outpatient diabetic cats

BACKGROUND

Interstitial glucose (IG) concentration measurement using a flash glucose monitoring system (FGMS) is a noninvasive, affordable, and informative method to regulate patients with diabetes mellitus (DM) but has not been fully validated in outpatient cats with DM.

OBJECTIVES

To further validate the FreeStyle Libre FGMS in outpatient diabetic cats.

ANIMALS

Eight client-owned cats with DM.

METHODS

Prospective observational validation study. Tissue glue was used to attach the sensor to the cat. Lin's concordance correlation coefficient (ρc ) was used to compare IG concentrations measured by the FGMS to blood glucose concentrations measured using an automated biochemistry analyzer (ABA) and point-of-care glucometer (POCG).

RESULTS

Data from 15 sensor placements in 8 cats were analyzed. Paired IG and ABA glucose concentrations (139 samples) had excellent correlation (ρc  = 0.96) as did IG and POCG glucose concentrations (142 samples, ρc  = 0.92). Sensor failure or displacement were recorded for 12/15 (80%) sensor placements. Median time of sensor activity was 7 days (range, 2-13 days).

CONCLUSIONS AND CLINICAL IMPORTANCE

In outpatient cats with DM, the FGMS-measured IG concentration correlated well with ABA-measured blood glucose concentration, but a high rate of sensor failures was observed.

Evaluation of fructosamine concentration as an index marker for glycaemic control in diabetic dogs

BACKGROUND

Although fructosamine is a commonly used surrogate marker to assess glycaemic control in diabetic dogs, its diagnostic accuracy has been questioned. The main objective of this study was to evaluate the reliability of fructosamine measurements to diagnose well and poorly controlled diabetes mellitus (DM), using continuous glucose monitoring as a gold standard.

METHODS

Twenty-four dogs with treated DM and continuous glucose monitoring for mean (±SD) 13.1 (±1.7) days were retrospectively analysed. Two assessment strategies were applied to categorize glycaemic control, and fructosamine concentrations were determined shortly after sensor cessation using a colorimetric assay.

RESULTS

Correlations of individual fructosamine concentrations with mean glucose as well as percentage of measurements > 15 mmol/L were not significant (p = 0.372, p = 0.129). Fructosamine did not differ between dogs with and without hypoglycaemic episodes (p = 0.64). Receiver operating characteristic analysis for fructosamine to diagnose either good or poor glycaemic control revealed AUC values of 0.71 (p = 0.025) indicating moderate accuracy, and 0.7 (p = 0.135) indicating AUC is non-discriminatory, respectively. The respective positive likelihood ratios for the optimal cutoffs to identify good (<396 μmol/L) and poor control (>449 μmol/L) were three.

CONCLUSIONS

Fructosamine measurement is an imperfect surrogate marker for classifying glycaemic control in diabetic dogs and can only complement serial glucose measurements.

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

Simple Summary

A flash glucose monitoring system (FGMS) has been validated for use in dogs with diabetes mellitus and diabetic ketoacidosis. It continuously measures the glucose in the interstitial fluid through a small filament (5 mm long) inserted under the skin. Interstitial glucose concentrations are reportedly comparable to whole blood glucose concentrations. However, several factors can influence the performance of interstitial sensors, including the proportion of interstitial fluid in a tissue. The influence of skin thickness on flash glucose monitoring system accuracy has not been investigated in previous studies; therefore, the aim of this study was to evaluate whether FGMS accuracy is affected by skin thickness. On the basis of our results, skin thickness seems to affect FGMS measurements; the mean bias was significantly inversely correlated (p = 0.02; r = −0.6) with the mean skin thickness, and clinical accuracy according to ISO 15197:2013 criteria was observed only in dogs with skin thickness > 5 mm, with 99% of the results falling in zone A + B of the Parkes consensus error grid analysis. In dogs with thin skin (<5 mm), the clinical accuracy was low, and the results should be interpreted with caution.

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.