Evaluation of a continuous glucose monitoring system compared with an in-house standard laboratory assay and a handheld point-of-care glucometer in critically ill neonatal foals

Evaluation of point-of-care capillary and venous blood glucose concentrations in hospitalized neonatal foals

OBJECTIVE

To compare glucose measurements from capillary and venous blood samples using a point-of-care (POC) glucometer with a standard laboratory (colorimetric, glucose oxidase) assay (LABGLU) in a population of hospitalized, neonatal foals.

DESIGN

Multicenter, prospective, experimental study, conducted between March 2019 and June 2020.

SETTING

Four university teaching hospitals and 1 private referral hospital.

ANIMALS

Fifty-four hospitalized neonatal (≤30 days of age) foals.

INTERVENTIONS

Simultaneous capillary (muzzle, POCMUZ) and venous (jugular, POCJUG) blood samples were obtained to determine POC glucose concentrations. Venous samples were also analyzed by LABGLU. Each foal was sampled at the time of enrollment or admission to the hospital and at 1 subsequent point during hospitalization. Indirect mean arterial pressure and hematocrit were concurrently recorded.

MEASUREMENTS AND MAIN RESULTS

Bland-Altman analysis showed a mean bias (95% limits of agreement) of -28.0 (-88.6 to 32.6) mg/dL for comparison of POCJUG with LABGLU, -8.2 (-94.3 to 78.0) mg/dL for POCMUZ and LABGLU, and 18.8 (-44.4 to 82.0) mg/dL for POCMUZ and POCJUG. A total of 63.5% of the POCJUG and 45.2% of the POCMUZ samples exceeded the reference value by ±15 mg/dL (for LABGLU samples <75 mg/dL) or ±15% (for LABGLU samples ≥75mg/dL). Concordance correlation coefficient (95% confidence interval [CI]) indicated a fair agreement between POCJUG and LABGLU (0.75, 95% CI: 0.66-0.82) and between POCMUZ and LABGLU (0.71, 95% CI: 0.58-0.80). Fifty percent (14/28) of hypoglycemic foals on the reference method were incorrectly classified as euglycemic by POCJUG, and 5 of 28 were incorrectly classified by POCMUZ.

CONCLUSIONS

In the sampled population, the chosen POC glucometer lacked agreement with the standard laboratory measurement. Limits of agreement were wide for both POCJUG and POCMUZ. Inaccuracies in POC results could impact decision-making in the clinical management of glycemic control in hospitalized neonatal foals and, importantly, increase the risk of hypoglycemic events being underdiagnosed in critical patients.

Accuracy and validation of a point-of-care blood glucose monitoring system for use in horses

Abnormal blood glucose (BG) levels often seen in critically ill horses are significantly associated with adverse patient outcomes and increased mortality. Rapid and accurate BG monitoring is now considered an essential component of evidence-based equine practice and can provide critical information quickly for treatment. Although several point-of-care (POC) BG monitoring hand-held devices are commercially available for veterinary use, none contains a unique algorithm validated for use in horses. The AlphaTrak 3 (AT3) BG monitoring system is a first-of-its-kind device with an equine-specific algorithm that allows stall-side clinical decision making, and frequent monitoring at minimal cost. As such, AT3 is potentially a preferred alternative to more costly and time-consuming standard diagnostic reference laboratory methods. The objective of this study was to determine the accuracy of the AT3 device in measuring BG levels in equine whole blood samples in comparison to results obtained by the Beckman Coulter AU480 reference analyzer per ISO15197:2013 specifications. Accuracy of the AT3 equine algorithm were initially verified by testing equine blood samples with artificially adjusted blood glucose levels followed by its validation in a field study. Testing with artificially adjusted equine samples (n = 129) showed that 98.9% of glucose measurements ranging from 29 to 479 mg/dL fell within ISO accuracy threshold of ±15 mg/dL or ±15% of the average reference value. In addition, 100% of the AT3 measurements fell in consensus error grid (CEG) zone A, which indicates that test outcomes have a minimal likelihood of adverse clinical impact. In a follow-up field study involving 96 horses, 98.4% of AT3 measurements met the ISO accuracy threshold and 99.2% of AT3 measurements fell in CEG zone A. These results demonstrate that the AT3 glucometer has a high degree of accuracy in horses and is a dependable, convenient, and cost-effective device for accurately monitoring equine BG levels in farm or clinical settings.

Use of FreeStyle Libre for continuous glucose monitoring in adult horses

OBJECTIVES

To evaluate the feasibility of using the FreeStyle Libre (a continuous glucose monitoring system [CGMS]) for instantaneous continuous monitoring of interstitial glucose in adult horses and examine the applicability and accuracy of this system in horses submitted to combined glucose-insulin test (CGIT).

DESIGN

Laboratory measurements and continuous glucose monitoring system (CGMS) readings were analyzed using a 2 × 2 factorial statistical model with repeated measures over time. This analysis assessed the effects of the test (factor 1), group (factor 2), and their interactions (test × group, test × time, and group × time). Pearson's correlation analysis was applied to blood glucose values. Mean comparisons were conducted using the t-test, and agreement between techniques was assessed via the Bland-Altman method, with a 95% confidence interval.

SETTING

Field study on private horse farms in association with a veterinary school.

ANIMALS

Ten healthy stallions were assigned to one of two groups based on their body condition scores (BCS). Group 1 (G1, n = 5) consisted of nonobese horses with a BCS of 5 or 6, while Group 2 (G2, n = 5) consisted of obese horses with a BCS of 7 or higher.

INTERVENTIONS

A CGMS sensor was attached to the dorsolateral aspect of the proximal one third of each horse's neck. Laboratory blood glucose measurements and CGMS interstitial glucose readings were compared at different time points for up to 7 days after sensor fixation. Obese horses were also submitted to CGIT on Day 4.

MEASUREMENTS AND MAIN RESULTS

A comparative analysis of glucose measurements obtained in G1 and G2 horses using the CGMS and enzymatic methods revealed significant group × time interactions (P < 0.001) and time effects (P < 0.001). No interactions were detected between group (P = 0.45), test (P = 0.62), group and test (P = 0.28), or time and test (P = 0.92). In G1 and G2, tests were significantly correlated (r = 0.84 and P = 0.00) at all time points (T0-T5). Agreement between the glucose values obtained using different methods was excellent despite a small time delay in CGMS detection of rapid changes in blood glucose.

CONCLUSIONS

It was concluded that the CGMS can be used for indirect assessment of glycemic status (ie, based on interstitial glucose measurements) in nonobese and obese adult horses submitted to CGIT.

Comparison of two glucose-monitoring systems for use in horses

OBJECTIVE

To determine the accuracy of 2 interstitial glucose-monitoring systems (GMSs) for use in horses compared with a point-of-care (POC) glucometer and standard laboratory enzymatic chemistry method (CHEM).

ANIMALS

8 clinically normal adult horses.

PROCEDURES

One of each GMS device (Dexcom G6 and Freestyle Libre 14-day) was placed on each horse, and blood glucose concentration was measured via POC and CHEM at 33 time points and compared with simultaneous GMS readings. An oral glucose absorption test (OGAT) was performed on day 2, and glucose concentrations were measured and compared.

RESULTS

Glucose concentrations were significantly correlated with one another between all devices on days 1 to 5. Acceptable agreement was observed between Dexcom G6 and Freestyle Libre 14-day when compared with CHEM on days 1, 3, 4, and 5 with a combined mean bias of 10.45 mg/dL and 1.53 mg/dL, respectively. During dextrose-induced hyperglycemia on day 2, mean bias values for Dexcom G6 (10.49 mg/dL) and FreeStyle Libre 14-day (0.34 mg/dL) showed good agreement with CHEM.

CLINICAL RELEVANCE

Serial blood glucose measurements are used to diagnose or monitor a variety of conditions in equine medicine; advances in near-continuous interstitial glucose monitoring allow for minimally invasive glucose assessment, thereby reducing stress and discomfort to patients. Data from this study support the use of the Dexcom G6 and Freestyle Libre 14-day interstitial glucose-monitoring systems to estimate blood glucose concentrations in horses.

Human continuous glucose monitors for measurement of glucose in dairy cows

If validated for use in dairy cattle, interstitial continuous glucose monitors (CGMs) could be easily implemented, informative tools for research, clinical, and perhaps even on-farm applications. To evaluate their efficacy, 2 experiments were conducted, during which lactating Holstein cows were fit with indwelling jugular catheters, as well as FreeStyle Libre (FSL; Abbott) and Dexcom G6 (DexCom Inc.) CGMs secured either behind their polls, lateral to their ears, or beneath their pin bones on their upper rear legs. During the first experiment, blood (measured with a handheld glucometer) and interstitial glucose measurements were collected from 13 cows every 4 h for 96 h. In the second experiment, the same measurements were collected from 8 cows every 15 min for 6 h. At the mid-point of the sampling period (3 h), cows received a bolus dose of dextrose to facilitate comparisons across a broad range of glucose concentrations. Results from both experiments determined that functional longevity of the sensors was greatest for those sensors secured near the ear. Likewise, interstitial measurements from the ear sensors were most closely correlated with blood glucose concentrations (r = 0.82 and r = 0.71 for FSL ear and Dexcom G6 ear, respectively). Unfortunately, accuracy calculated as absolute relative error was low, at 60.7% or less. As a result of the low accuracy, even though both ear sensors detected an increase in glucose concentrations following the bolus dose, neither produced results exactly matching blood glucose measurements. The results of this work indicate that the FSL and Dexcom G6 CGMs are not currently capable of replacing blood-based glucose measurements.

Evaluation of a continuous glucose monitoring system in neonatal foals

Background

Monitoring blood glucose concentrations is common in critically ill neonatal foals, especially septic foals and those receiving naso‐esophageal feedings or IV parenteral nutrition. Glucose typically is measured using a point‐of‐care (POC) glucometer but requires repeated restraint and blood collections, which may cause irritation at venipuncture sites and increased demands on nursing staff. Continuous glucose monitoring systems (CGMS) may provide an accurate alternative for monitoring blood glucose concentration.

Objectives

To determine the correlation and accuracy of a CGMS to monitor neonatal foals' blood glucose concentrations as compared to a POC glucometer and laboratory chemistry analysis (CHEM).

Animals

Samples from 4 healthy and 4 ill neonatal foals.

Methods

A CGMS was placed on each foal, and glucose measurements acquired from this device were compared to simultaneous measurements of blood glucose concentration using a POC glucometer and CHEM.

Results

Two‐hundred matched glucose measurements were collected from 8 neonatal foals. The mean bias (95% limits of agreement) between CGMS and CHEM, CGMS and POC glucometer, and POC glucometer and CHEM was 3.97 mg/dL (−32.5 to 40.4), 18.2 mg/dL (−28.8 to 65.2), and 22.18 mg/dL (−9.3 to 53.67), respectively. The Pearson's correlation coefficient (r) was significantly correlated among all devices: GCMS and CHEM (r = 0.81), CGMS and POC glucometer (r = 0.77) and POC glucometer‐CHEM (r = 0.92).

Conclusions and Clinical Importance

Within the blood glucose concentration ranges in this study (78‐212 mg/dL), CGMS measurements were significantly correlated with CHEM, suggesting that it is an acceptable method to provide meaningful, immediate, and continuous glucose concentration measurements in neonatal foals while eliminating the need for repeated restraint and blood collection.

Blood glucose and subcutaneous continuous glucose monitoring in critically ill horses: A pilot study

This pilot prospective study reports the feasibility, management and cost of the use of a continuous glucose monitoring (CGM) system in critically ill adult horses and foals. We compared the glucose measurements obtained by the CGM device with blood glucose (BG) concentrations. Neonatal foals (0–2 weeks of age) and adult horses (> 1 year old) admitted in the period of March-May 2016 with clinical and laboratory parameters compatible with systemic inflammatory response syndrome (SIRS) were included. Glucose concentration was monitored every 4 hours on blood samples with a point-of-care (POC) glucometer and with a blood gas analyzer. A CGM system was also placed on six adults and four foals but recordings were successfully obtained only in four adults and one foal. Glucose concentrations corresponded fairly well between BG and CGM, however, there appeared to be a lag time for interstitial glucose levels. Fluctuations of glucose in the interstitial fluid did not always follow the same trend as BG. CGM identified peaks and drops that would have been missed with conventional glucose monitoring. The use of CGM system is feasible in ill horses and may provide clinically relevant information on glucose levels, but there are several challenges that need to be resolved for the system to gain more widespread usability.

Comparison of a continuous indwelling glucometer with a point-of-care device in healthy adult horses

BACKGROUND

Blood glucose is tightly regulated in horses; however, since hypoglycaemia and hyperglycaemia are associated with poor prognosis, close monitoring is warranted. This study aimed at evaluating a continuous indwelling glucometer (CIG) by comparing performance with a point-of-care glucometer (POC).

METHODS

Ten horses were equipped with CIG and an intravenous catheter. Interstitial glucose concentrations were determined by CIG every 5 min at rest, during insulin-induced hypoglycaemia and dextrose-induced hyperglycaemia, and compared with blood glucose determined by POC. Glucose concentrations were compared by two-way repeated measures analysis of variance and weighted kappa with Bland-Altman plots to determine agreement between assays.

RESULTS

Horses tolerated CIG well; however, five devices had to be replaced. There were no statistically significant differences between assays at rest or during hyperglycaemia; however, during hypoglycaemia, glucose concentrations determined by CIG were significantly higher (P=0.01). The mean bias (95% limits of agreement) between assays ranged from -0.03 (-2.46 to 2.52) mmol/l (hyperglycaemia) to 0.97 (-1.23 to 3.16) mmol/l (hypoglycaemia). Assay agreement was 'good' with observed agreements of 87.04% (κ=0.67).

CONCLUSIONS OF THE STUDY

CIG has acceptable accuracy in horses as compared with POC but overestimates glucose concentrations during hypoglycaemia and requires frequent replacement, limiting its clinical application.

Blood-glucose levels in newborn piglets and the associations between blood-glucose levels, intrauterine growth restriction and pre-weaning mortality

Objectives

The aim of this study was to investigate the associations between blood-glucose levels in one-day-old-piglets (ODOP), intrauterine growth restriction (IUGR) and pre-weaning mortality in a commercial piglet-producing herd in Norway.

Material and methods

The study was carried out in a non-crate commercial piglet-producing herd in Norway and 426 live born piglets from 31 litters were included. Piglets were blood-sampled, ear tagged, weighed and measured within 24 h after birth. Litter size, cross fostering and deaths until weaning were recorded. Blood was collected by vein puncture of Vena subcutanea abdominis and blood-glucose levels were measured using a handheld glucometer. Piglets were given an IUGR-score (1–3) based on head-morphology where a score of 3 is defined as an intrauterine growth restricted piglet.

Results

Of the 426 live born piglets, 391 piglets survived until weaning, resulting in 8.22% pre-weaning mortality. Mean piglet weight in ODOP was 1.59 kg (SD = 0.36), and mean blood-glucose level was 5.48 mmol/l (SD = 1.44). IUGR score 3 piglets had lower blood-glucose levels (Coef. = − 1.7 mmol/l, P < .001) than normal piglets (IUGR score 1). Males had significantly higher blood glucose levels (Coef. = 0.23 mmol/l, P = .044) compared to females. There was a trend that blood-glucose levels in individual piglets were lower in large litters with − 0.07 mmol/l per extra piglet born (P = .054). Piglets with blood-glucose levels in the second quartile had reduced risk of pre-weaning mortality (OR = 0.32, P = .046) compared to piglets with blood-glucose levels in the lower quartile. This is also true for piglets in the third and fourth quartile (OR = 0.13, P = 0.004).

Conclusion

This study identified IUGR to be associated with low blood-glucose levels in ODOP. It also found increased pre-weaning mortality in ODOP with low blood-glucose. By identifying IUGR piglets by the shape of their head, piglet producers may reduce pre-weaning mortality by making sure these piglets get enough colostrum, milk or supplement feeding (i.e. energy).

Precision and accuracy of a point-of-care glucometer in horses and the effects of sample type

Point-of-care glucometry is used commonly in clinical and research settings; however, accuracy and precision of this method are concerns. The objectives of this study were to determine the accuracy of glucometry in adult horses and the precision of duplicate measurements. Blood samples were collected from 62 horses into one plain syringe, one EDTA tube and three fluoride oxalate (FO) tubes. Immediately after collection, glucose concentrations in whole blood were determined, in duplicate, by glucometry from the syringe (plain whole blood [WB] group), EDTA tube (EDTA group) and one FO tube (FO group). One FO sample was used to measure plasma glucose concentration by a laboratory chemistry analyser (LAB group) ≤1 h after collection. The third FO tube was used to measure plasma glucose concentration by glucometry after 3 h storage (FO3hr group). Adequate precision was present for all groups (coefficient of variation: 0.7-3.5%) except WB (5.5-9.4%). Between groups, correlations were significant (P < 0.05; except for WB-EDTA), varied with group comparison, and tended to be lowest for comparisons involving WB. Mean bias was lowest for WB-LAB and greatest for FO-LAB and FO3hr-LAB; however, the limits of agreement were ≥4.65 mmol/L for WB-LAB and ≤2.75 mmol/L for most other comparisons. For the glucometer used, performance was influenced by sample type: WB was unsuitable, while FO or EDTA samples resulted in adequate precision and accuracy, provided under-estimation of glucose concentrations is accounted for by using method-specific reference ranges. Glucometer performance and optimal sample type(s) should be determined prior to use in horses.

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.

The clinical value of whole blood point-of-care biomarkers in large animal emergency and critical care medicine

OBJECTIVE

To summarize the current medical literature and provide a clinical perspective of whole blood point-of-care (POC) biomarkers in large animal emergency and critical care practice.

DATA SOURCES

Original studies, reviews, and textbook chapters in the human and veterinary medical fields.

SUMMARY

POC biomarkers are tests used to monitor normal or disease processes at or near the patient. In both human and veterinary medicine these tools are playing an increasingly important role in the management of critical diseases. The most important whole blood POC biomarkers available for veterinary practitioners include l-lactate, cardiac troponin I, serum amyloid A, triglyceride, creatinine, and glucose, although many other tests are available or on the horizon.

CONCLUSION

Whole blood POC biomarkers enable clinicians to provide improved management of critical diseases in large animals. These tools are especially useful for establishing a diagnosis, guiding therapy, and estimating disease risk and prognosis.