Evaluation of the Accuracy of FreeStyle Libre 2 for Glucose Monitoring in White New Zealand Rabbits

BACKGROUND

Studies are currently being conducted on rabbits requiring serial glucose monitoring. The FreeStyle Libre 2 (FSL2), a serial glucose monitoring device, has been validated in humans, dogs and cats, but not in rabbits.

OBJECTIVES

This study aimed to evaluate the accuracy of the FSL2 in rabbits.

METHODS

Six healthy rabbits were used in this study. Interstitial glucose (IG) was measured using the FSL2, and blood glucose (BG) was measured using a portable blood glucose meter (PBGM); their results were compared with those from a clinical chemistry analyser. For the first 3 h, IG and BG were measured at 1-h intervals. Subsequently, they were measured every 8 h over a 48-h period. Regular insulin 0.2 U/kg was then administered to the rabbits, and IG and BG were measured every 15 min over a 90-min period.

RESULTS

Before insulin treatment, no measurements fell within the hypoglycaemic range (BG < 100 mg/dL). In the euglycaemic range (BG ≥ 100 mg/dL), the PBGM and FSL2 showed 85.7% and 23.8% accuracies, respectively. After insulin treatment, the PBGM showed 95.5% and 81.3% accuracies in the hypoglycaemic and euglycaemic ranges, respectively. The FSL2 showed 68.1% and 37.5% accuracies in the hypoglycaemic and euglycaemic ranges, respectively. Parkes consensus error grid analysis showed that the PBGM and FSL2 had 100% agreement for Zones A (no effect on clinical action) and B (altered clinical action unlikely to affect outcome) in rabbits with and without insulin treatment.

CONCLUSIONS

There was limited agreement between the FSL2 and reference standard BG measurements. However, the FSL2 allows clinically acceptable identification of hypoglycaemic states in rabbits.

Dietary supplement guava leaf extract regulates growth, feed utilization, immune function, nutrient digestibility and redox regulation in growing rabbits

The use of agricultural waste in animal production has gained global interest. An eight-week trial was conducted to investigate the impacts of adding ethanolic guava leaf extract (GLE) as a feed supplement on the growth, feed utilization, immune response, nutrient digestibility, redox regulation, and blood health of growing rabbits. Ninety weaned growing rabbits were randomly assigned to three groups. The first group was fed a basal diet (GLE0), while the other two groups were fed the control diet fortified with 15 mg (GLE15) or 20 mg (GLE20) of GLE per kg of diet for 8 weeks. The HPLC analysis of GLE exhibited the presence of gallic acid, ferulic acid, catechin, and caffeic acid in significant amounts. The results indicated that final body weight, daily body weight, daily feed intake and nutrient digestibility were significantly higher in the GLE-treated groups compared to the un-treated group (p < 0.05). Dietary supplementation of GLE significantly reduced lipid contents including triglycerides, total cholesterol, LDL, HDL, and VLDL (P < 0.05), with the most significant results observed when adding 20 mg/kg to the diet. AST and ALT levels as well as cortisol hormone in rabbits fed GLE were lower than those in the GLE0 group (P < 0.05). Immunoglobulins (IgG and IgA), antioxidant biomarkers (SOD and TAC) and T3 hormone were significantly improved by GLE supplementation (P < 0.001). Rabbits fed with GLE had lower levels of ROS and MDA compared to those in the GLE0 group (P < 0.001). Moreover, the hepatic and intestinal architectures were maintained in all rabbits fed diets with GLE. The results suggest that GLE supplementation (20 mg/kg diet) in fattening rabbit diets could efficiently improve growth, health status, blood physiology, antioxidant capacity and tissue histology.

Evaluating the Bias of Two Point-of-Care Glucometers for Calves and Ewes: Awareness for Ruminant Practitioners

(1) Background: Multiple point-of-care (POC) glucometers are in use in veterinary medicine, but few are compared to each other. This leaves the potential for clinicians to be unaware of the effect of bias when comparing results from different POC glucometers. (2) Methods: Samples from healthy calves and ewes were simultaneously compared with two POC veterinary glucometers, the Precision Xtra and the AlphaTrak2, under both the “canine” and “feline” settings. The results of each sample were statistically analyzed with linear regression and Bland–Altman analysis. (3) Results: 170 samples from healthy calves and 108 samples from healthy ewes were available for comparison. Calves: The AT2 consistently overestimated blood glucose concentrations when compared to the PX device with the calves. Correlationt with the PX was r = 0.8496 (canine setting) and r = 0.8861 (feline setting). Both the canine and feline settings demonstrated a consistent bias (41.11 and 33.64 mg/dL, respectively). Ewes: The AT2 consistently overestimated blood glucose concentrations when compared to the PX device with the ewes. Correlation with the PX was R = 0.4710 (canine setting) and R = 0.7269 (feline setting). Both the canine and feline settings demonstrated a consistent bias (21.23 and 14.54 mg/dL, respectively). (4) Clinicians should be aware of the potential for consistent bias when evaluating calf and sheep blood glucose concentrations as the AT2 device, at both settings, overestimated blood glucose compared to the previously validated PX. This reliability appears to change when the values are farther from the normal ranges, which should be considered when making clinical decisions based on data from these devices.

Rabbit Pediatrics

Rabbits encompass roles spanning from companion animals, wildlife species to laboratory animal models. Pediatric care of these species therefore may extend to various disciplines of veterinary medicine. Rabbits are born altricial but have a unique perinatal relationship between kit and doe with infrequent nursing. Nursing is immunologically protective to the kit and close contact with the doe allows for colonization of their gastrointestinal tract with bacterial flora. The most common diseases that pediatric rabbits are faced with are gastrointestinal in nature with orphaned and hand-reared rabbits at higher risk due to the aforementioned effects on their immune system.

Diagnostic agreement between three point-of-care glucose and β-hydroxybutyrate meters and reference laboratory methods in stingrays

Point-of-care (POC) glucose and β-hydroxybutyrate (β-HB) meters can potentially provide rapid insight into an elasmobranch's metabolic state in clinical and field research settings. This study evaluated the diagnostic agreement of three commercial POC meters against reference laboratory methods for glucose and β-HB concentrations in stingrays. Blood was collected during anesthetized exams from 28 stingrays representing four species: cownose rays (Rhinoptera bonasus), Atlantic stingrays (Hypanus sabina), southern stingrays (Hypanus americanus), and yellow stingrays (Urobatis jamaicensis). Glucose and β-HB concentrations were measured with each POC meter using whole blood and plasma; in parallel, plasma glucose and β-HB concentrations were measured via reference laboratory methods. Agreement between POC meters and reference laboratory methods was assessed using Bland-Altman methods, Passing-Bablok regression, observed total error, percent relative error, and linear mixed effect models. Plasma glucose and β-HB concentrations determined by reference laboratory methods ranged from <20-63 mg/dL to 0.05-5.38 mmol/L, respectively. One human POC meter-the Precision Xtra-showed the greatest agreement with reference laboratory methods when measuring glucose with whole blood [mean bias and 95% CI: 0 (-3-4) mg/dL] and β-HB with plasma [mean bias and 95% CI: 0.1 (-0.04-0.2) mmol/L]. Stingray sex, weight, buffy coat, and packed cell volume did not significantly affect the agreement between POC meters and reference laboratory methods. Across all three POC meters, mean bias and imprecision for plasma β-HB concentrations were relatively small (0-0.1 mmol/L and 0%, respectively). Utilizing POC meters to measure glucose and β-HB in stingrays may be viable when reference methods are unavailable.

Nutritive Support for Critical Exotic Patients

Malnutrition and need for nutritive support are both very common in exotic animals requiring critical care. Assessment and monitoring of body condition, weight, protein absorption, and catabolic loss is recommended to help guide restorative therapy. Several critical care diets are available based on digestive strategy. Fluid requirements and evaporative water loss can vary based on taxa; ectoderms suffer evaporative losses at a greater magnitude than endotherms. Enteral and parenteral nutrition strategies can be appropriate for patients, with natural history and anatomic and physiologic differences considered as much as possible.

Endocrine Diagnostics for Exotic Animals

Endocrine disease in exotic species is less common than in small animals. Nevertheless, the diagnostic principles used in small animals can be adapted to evaluate endocrine disease in many of the exotic species although species-specific aspects need to be considered. This article covers important diseases such as thyroid dysfunction in reptiles and birds, hyperthyroidism in guinea pigs, and hyperadrenocorticism in ferrets. Glucose metabolism in neoplasms affecting normal physiology, such as insulinoma in ferrets and gastric neuroendocrine carcinoma in bearded dragons, is discussed. Calcium abnormalities, including metabolic bone disease in reptiles and hypocalcemia in birds, are also covered.

Analytical validation of a portable human Accu-Chek glucometer in honeybee hemolymph

Glucose and trehalose are the main energy sources used by honeybees (Apis mellifera) for daily activities. However, there is no validated point-of-care method to reliably measure both sugars. We performed an analytical validation of a portable human glucometer (Accu-Chek; Roche) for glucose measurement in honeybee hemolymph compared to a reference method (GluCH, UniCel DxC 600; Beckman Coulter). We used 30 pooled hemolymph samples collected from the antennae of anesthetized honeybees and diluted 1:4 in 0.9% saline. We evaluated dilution linearity, spike recovery, and inter- and intra-assay imprecision. Glucose concentration was measured over time (2 h, 4 h, 8 h, 12 h, 1 d, 2 d, 3 d, 7 d, 21 d, 28 d) at various storage temperature (25°C, 4°C, -20°C, -80°C). The trehalose concentration was measured indirectly by trehalase hydrolyzation. Glucose concentrations measured by both instruments had a strong correlation (0.985, p < 0.0001) and a bias of -7.33 mmol/L (±1.96SD: 13.70 to -28.36), with linear agreement at <20 mmol/L (physiologic value: 100 mmol/L). The accuracy of the glucometer decreased at >20 mmol/L. Recovery of 115-130% of diluted spikes indicated good specificity. Inter- and intra-assay imprecision were 2.50% and 2.21%, respectively. Glucose concentrations fluctuated in stored samples dependent on time and temperature; however, glucose concentrations were constant with storage at -80°C for ≥28 d. The Accu-Chek glucometer is an adequate instrument to measure honeybee glucose concentration in hemolymph diluted with 0.9% NaCl, with good accuracy and precision at <20 mmol/L. Hemolymph storage at -80°C is suitable for long-term conservation of glucose.

Glucose and Lactate Reference Intervals for White Sturgeon and Evaluation of Two Point-of-Care Devices in Sturgeon Infected with Veronaea botryosa

White Sturgeon Acipenser transmontanus are cultured for human consumption as well as for conservation purposes. In this study, two commercially available portable devices for measuring glucose and lactate were compared to a benchtop analyzer and blood reference intervals were generated using heparin plasma collected from 43 healthy White Sturgeon yearlings. The generated normal ranges were used to compare plasma values collected from Veronaea botryosa-infected White Sturgeon at 10, 20, and 30 d postchallenge (dpc). In the 43 healthy yearlings, significantly different glucose and lactate values were obtained when comparing the portable devices to the benchtop analyzer. In the portable devices, blood glucose showed a consistent bias of 12.3 mg/dL and blood lactate showed a proportional bias. The detected blood glucose values in infected sturgeon were significantly different from those in noninfected controls when using the benchtop analyzer at 20 and 30 dpc and when using the portable device at 20 dpc. However, blood glucose in infected individuals and controls was within the reference interval on either device. No significant difference was noted for lactate measurements in infected sturgeon. The results of this study indicate that portable devices for blood glucose and blood lactate evaluation in White Sturgeon may be useful in a setting where relative values are an acceptable approximation of absolute values.

Comparison of 2 glucose analytical methodologies in immature Kemp's ridley sea turtles: dry chemistry of plasma versus point-of-care glucometer analysis of whole blood

Blood glucose measurements provide important diagnostic information regarding stress, disease, and nutritional status. Glucose analytical methodologies include dry chemistry analysis (DCA) of plasma and point-of-care (POC) glucometer analysis of whole blood; however, these 2 methods differ in cost, required sample volume, and processing time. Because POC glucometers use built-in equations based on features of mammalian blood to convert whole blood measurements to plasma equivalent units, obtained glucose data must be compared and validated using gold-standard chemistry analytical methodology in reptiles. For in-water, trawl-captured, immature Kemp's ridley sea turtles (Lepidochelys kempii) from Georgia, USA, we observed significant, positive agreement between the 2 glucose determination methods; however, the glucometer overestimated glucose concentrations by 1.4 mmol/L on average in comparison to DCA and produced a wider range of results. The discordance of these results suggests that POC glucometer glucose data should be interpreted in the context of methodology- and brand-specific reference intervals along with concurrent packed cell volume data.

Associations between biochemical parameters and referral centre in pet rabbits with urolithiasis

OBJECTIVES

To determine the association between signalment, selected haematologic and biochemical parameters and referral centre in pet rabbits with imaging evidence of urolithiasis presented to two veterinary teaching hospitals in North America.

MATERIALS AND METHODS

The medical record database of two veterinary teaching hospitals was searched from 2009 to 2019 for records of pet rabbits that received both imaging studies and plasma biochemistry profiles. Information regarding signalment, bodyweight, packed cell volume, total solids, and plasma biochemistry profiles was obtained. Univariable and multivariable logistic regression models were performed to identify statistically significant parameters associated with imaging evidence of urolithiasis.

RESULTS

Of the 324 examined rabbits, 33 (10.2%) had confirmed evidence of urolithiasis on imaging. Increasing plasma calcium and sodium concentrations and referral centre were significantly associated with the presence of urolithiasis on the univariable logistic regression model. However, only plasma calcium concentration and the referral centre demonstrated significant associations on the multivariable logistic regression model.

CLINICAL SIGNIFICANCE

Results indicate that urolithiasis in pet rabbits that receive imaging is associated with mildly increasing plasma calcium concentration and referral centre. The association with referral centre may indicate there are geographic influences on urolithiasis or on imaging. However, the identified associations have low predictive value for the diagnosis of urolithiasis, indicating the need for additional diagnostic modalities.

Comparison of 2 portable human glucometers for the measurement of blood glucose concentration in White New Zealand rabbits

We compared measurements of blood glucose concentrations in 30 healthy adult White New Zealand rabbits using 2 commercial portable glucometers (PGM1 and PGM2) and a laboratory chemical analyzer. Results were analyzed with Pearson correlation, Passing-Bablok regression analysis, Bland-Altman analysis, and a modified error grid. Measurements with PGM1 were significantly correlated (r = 0.37) with those obtained from the laboratory reference method (RM); Bland-Altman and Passing-Bablok analyses indicated no significant systematic or proportional differences (mean difference of -0.26, 95% CI of mean difference of -0.54 to 0.01, and LOA of -1.70 to 1.17); and error grid resulted in 100% of measurements in zone A. No significant correlation (r = -0.05) was detected between PGM2 and RM; Bland-Altman and Passing-Bablok analyses results indicated a mean difference of 2.14, 95% CI of mean difference of 1.67-2.60, and limit of agreement of -0.32 to 4.59, which overestimated blood glucose concentration, with 53% of glucose measurements in error grid zone A and 47% in zone B. PGM1 was considered accurate in normoglycemic rabbits, whereas the use of PGM2 could result in overestimations of glycemia.

Investigation for correction formulas on the basis of packed cell volume for blood glucose concentration measurements obtained with portable glucometers when used in rabbits

OBJECTIVE

To determine effects of PCV on blood glucose (BG) concentration measurements obtained with a human portable blood glucometer (HPBG) and a veterinary portable blood glucometer (VPBG) on canine (cVPBG) and feline (fVPBG) settings (test methods) when used in rabbits and to develop correction formulas to mitigate effects of PCV on such measurements.

SAMPLE

48 resuspended blood samples with known PVCs (range, 0% [plasma] to 92% [plasma and packed RBCs]) from 6 healthy research rabbits (experimental sample set) and 252 historic measurements of BG concentration and PCV in 84 client-owned rabbits evaluated at a veterinary hospital (validation data set).

PROCEDURES

Duplicate measurements of BG concentration with each test method and of PCV were obtained for each sample in the experimental sample set, and the mean results for each variable for each test method and sample were compared with results from a clinical laboratory analyzer (reference method) used to determine the true BG concentration for each sample. Mean ± SD differences in measurements between the reference and test methods were calculated. Linear regression and modified Clarke error grid analysis were used to develop correction formulas for the test methods given known PCVs, and these formulas were evaluated on the validation data set with linear regression and a modified Clarke error grid.

RESULTS

Blood glucose concentrations were falsely low for cVPBG and fVPBG used on samples with PCV < 31% and were falsely high for all test methods used on samples with PCV > 43%. Compared with original measurements, formula-corrected measurements overall had better agreement with reference method measurements for the experimental sample set; however, only the formula-corrected HPBG measurements had improved agreement for the validation data set.

CONCLUSIONS AND CLINICAL RELEVANCE

Findings indicated that, in rabbits, HPBG measurements had improved accuracy with the use of the correction formula HPBG measurement of BG concentration + ([0.75 × PCV] - 15); however, the correction formulas did not improve the accuracy of VPBG measurements, and we believe that neither the cVPBG nor fVPBG should be used in rabbits.

Pre-/analytical factors affecting whole blood and plasma glucose concentrations in loggerhead sea turtles (Caretta caretta)

Blood glucose is vital for many physiological pathways and can be quantified by clinical chemistry analyzers and in-house point-of-care (POC) devices. Pre-analytical and analytical factors can influence blood glucose measurements. This project aimed to investigate pre-analytical factors on whole blood and plasma glucose measurements in loggerhead sea turtles (Caretta caretta) by evaluating the effects of storage (refrigeration) up to 48h after sampling and of packed cell volume (PCV) on whole blood glucose analysis by POC glucometer (time series n = 13); and by evaluating the effects of storage (room temperature and refrigeration) on plasma glucose concentrations using a dry slide chemistry analyzer (DCA) at various conditions: immediate processing and delayed plasma separation from erythrocytes at 24h and 48h (time series n = 14). The POC glucometer had overall strong agreement with the DCA (CCC = 0.76, r = 0.84, C_b = 0.90), but consistently overestimated glucose concentrations (mean difference: +0.4 mmol/L). The POC glucometer results decreased significantly over time, resulting in a substantial decline within the first 2h (0.41±0.47 mmol/L; 8±9%) that could potentially alter clinical decisions, thereby highlighting the need for immediate analysis using this method. The effects of PCV on glucose could not be assessed, as the statistical significance was associated with one outlier. Storage method significantly affected plasma glucose measurements using DCA, with room temperature samples resulting in rapid decreases of 3.57±0.89 mmol/L (77±9%) over the first 48h, while refrigerated samples provided consistent plasma glucose results over the same time period (decrease of 0.26±0.23 mmol/L; 6±5%). The results from this study provide new insights into optimal blood sample handling and processing for glucose analysis in sea turtles, show the suitability of the POC glucometer as a rapid diagnostic test, and confirm the reliability of plasma glucose measurements using refrigeration. These findings emphasize the need to consider pre-/analytical factors when interpreting blood glucose results from loggerhead sea turtles.

Evaluation of point-of-care analysers for blood gas and clinical chemistry in Hermann's tortoises (Testudo hermanni)

OBJECTIVE

To assess the agreement between point-of-care and laboratory analysers in measuring biochemical and blood gas analytes in venous samples from tortoises and to define preliminary reference intervals for venous blood gas analysis in Hermann's tortoises (Testudo hermanni).

MATERIALS AND METHODS

Jugular venous blood samples from 47 Hermann's tortoises underwent paired analysis with a portable gas analyser (i-STAT 1, Abaxis), a portable chemical analyser (VetScan VS2, Abaxis), and with the respective reference analysers. Agarose gel electrophoresis was used to determine albumin concentrations on 12 specimens. Agreement was evaluated with Bland-Altman plots and regression analysis using the Passing-Bablok method.

RESULTS

Point-of-care analysers had variable agreement with the reference analysers, presenting constant or proportional bias depending on the analyte. Relevant analytes in reptiles, such as ionised and total calcium, had acceptable agreement. The method for determining albumin concentration currently available in both point-of-care and laboratory analysers significantly overestimated albumin concentrations as compared to protein electrophoresis.

CLINICAL SIGNIFICANCE

While the use of POC analysers is extremely advantageous in small animal primary care facilities, agreement between point-of-care and laboratory analysers varies depending on the analyte. For certain analytes, interchangeability of results is limited and specific reference intervals for point-of-care analysers are required. Veterinarians should be aware of the size and the direction of the bias of each analyte.

Evaluation of a point-of-care blood glucose monitor in healthy goats

OBJECTIVE

To assess agreement between a point-of-care glucometer (POCG) and a laboratory chemistry analyzer for blood glucose measurements in goats.

DESIGN

Prospective study.

SETTING

University teaching hospital.

ANIMALS

Eighteen healthy adult goats.

INVESTIGATIONS

Whole blood samples were obtained via jugular venipuncture prior to premedication with xylazine and butorphanol (T0), following premedication (T20), and after 1 hour of inhalant anesthesia (T60). Each sample was tested with a POCG and a laboratory analyzer (HITA). Agreement was assessed using concordance correlation coefficients and calculation of bias and 95% limits of agreement.

MEASUREMENTS AND MAIN RESULTS

Mean blood glucose concentration at T0 was 3.9 ± 0.6 mmol/L (70 ± 10 mg/dL; POCG) and 2.9 ± 0.4 mmol/dL (53 ± 8 mg/dL; HITA). Glucose concentrations at T20 were 6.7 ± 2.4 mmol/L (121 ± 43 mg/dL) and 5.4 ± 2.1 mmol/L (97 ± 37 mg/dL) and at T60 were 5.7 ± 1.7 mmol/L (102 ± 31 mg/dL) and 4.7 ± 1.3 mmol/L (85 ± 24 mg/dL) when measured with the POCG and HITA, respectively. The POCG overestimated blood glucose compared to the HITA. The bias ± SD was 1.08 ± 0.53 mmol/L (19.4 ± 9.5 mg/dL) (95% LOA 0.04 to 2.11 mmol/L [0.7 to 38.0 mg/dL]) and the concordance correlation coefficient was 0.82. After correcting the results of the POCG using a mixed-effects linear model, the bias was 0.0 ± 0.38 mmol/L (0.0 ± 6.8 mg/dL) (95% LOA ± 0.74 mmol/L [± 13.4 mg/dL]) and the concordance correlation coefficient was 0.98.

CONCLUSIONS

The POCG overestimated blood glucose concentrations in goats, compared to the HITA, but when the POCG concentrations were corrected, the agreement was excellent.

Evidence-Based Advances in Rabbit Medicine

Rabbit medicine has been continuously evolving over time with increasing popularity and demand. Tremendous advances have been made in rabbit medicine over the past 5 years, including the use of imaging tools for otitis and dental disease management, the development of laboratory testing for encephalitozoonosis, or determination of prognosis in rabbits. Recent pharmacokinetic studies have been published, providing additional information on commonly used antibiotics and motility-enhancer drugs, as well as benzimidazole toxicosis. This article presents a review of evidence-based advances for liver lobe torsions, thymoma, and dental disease in rabbits and controversial and new future promising areas in rabbit medicine.

Point-of-care devices for physiological measurements in field conditions. A smorgasbord of instruments and validation procedures

Point-of-care (POC) devices provide quick diagnostic results that increase the efficiency of patient care. Many POC devices are currently available to measure metabolites, blood gases, hormones, disease biomarkers or pathogens in samples as diverse as blood, urine, feces or exhaled breath. This diversity is potentially very useful for the comparative physiologist in field studies if proper validation studies are carried out to justify the accuracy of the devices in non-human species under different conditions. Our review presents an account of physiological parameters that can be monitored with POC devices and surveys the literature for suitable quantitative and statistical procedures for comparing POC measurements with reference "gold standard" procedures. We provide a set of quantitative tools and report on different correlation coefficients (Lin's Concordance Correlation Coefficient or the more widespread Pearson correlation coefficient), describe the graphical assessment of variation using Bland-Altman plots and discuss the difference between Model I and Model II regression procedures. We also report on three validation datasets for lactate, glucose and hemoglobin measurements in birds using the newly proposed procedures. We conclude the review with a haphazard account of future developments in the field, emphasizing the interest in lab-on-a-chip devices to carry out more complex experimental measurements than the ones currently available in POC devices.