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.     

Evaluation of four portable blood glucose meters in diabetic and non-diabetic dogs and cats

Background: Monitoring of an animal's blood glucose concentration is critical for diagnostic and therapeutic decisions. Over the past few decades, portable blood glucose meters (PBGMs) have been used to monitor blood glucose concentrations in animals. Recently, new and improved PBGMs have been made available on the market.

Objective: The purpose of this study was to evaluate four PBGMs for use in dogs and cats.

Animals and methods: A total of 155 venous blood samples of dogs and 85 venous blood samples of cats were tested using four PBGMs. Control solutions from manufacturers were used to determine the precision of each meter. The coefficient of variation was calculated to determine precision during a set of replicates. Pearson's correlation analysis, Passing–Bablok regression, and Bland–Altman analysis were used to determine the accuracy of four PBGMs against the hexokinase reference method. Error grid analysis was used to evaluate clinical relevance.

Results: All PBGMs, except CERA-PET®, were clinically acceptable for monitoring blood glucose concentrations; AlphaTrak® and VetMate® appeared to be the most accurate ones, demonstrating that to use PBGMs for glucose monitoring, it is important to understand the strengths or limitations of each meter. The difference in results between the PBGMs and the reference method increased at high glucose concentration ranges, which were also affected by the hematocrit.

Conclusions: Although readings of the PBGMs and the reference method varied across glycemic ranges (low, normal, and high glucose concentrations), most PBGMs were clinically acceptable for monitoring blood glucose concentrations in dogs and cats.     

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.     

Comparison of glucose concentrations in canine whole blood,plasma, and serum measured with a veterinary point-of-care glucometer

Previous studies have determined that, compared to whole blood, serum or plasma used in a portable blood glucometer (PBG) may provide more accurate results. We investigated the accuracy of a veterinary PBG (AlphaTRAK 2; Zoetis) for the measurement of glucose concentrations in serum, plasma, and whole blood compared to plasma glucose concentration measured by a biochemical analyzer. Blood samples from 53 client-owned dogs were collected. Lin concordance correlation coefficient (ρ_c) and Bland–Altman plots were used to determine correlation and agreement between the results obtained for the different sample types. Glucose concentration in whole blood measured by the veterinary PBG was more strongly correlated with the glucose concentration measured by the biochemical analyzer (ρ_c = 0.92) compared to plasma and serum glucose concentrations (ρ_c = 0.59 and 0.57, respectively). The mean differences between the glucose concentrations in whole blood, plasma, and serum measured by the veterinary PBG and the glucose concentration determined by the biochemical analyzer were 1.0, 6.3, and 6.7 mmol/L (18, 113, and 121 mg/dL), respectively. Our findings suggest that, when using this veterinary PBG, the accuracy of a glucose measurement obtained is higher when using whole blood compared to plasma or serum. Use of whole blood allows for more correct assessment and diagnosis, which are necessary for appropriate therapeutic intervention.     

Evaluation of a portable glucose meter for use in cattle and sheep

Background: In farm animal practice, determination of blood glucose concentration under field conditions is often necessary. Objective: As there is no portable glucose meter device developed for use in farm animals, the analytical accuracy of a portable glucometer designed for people was evaluated for its use in cattle and sheep. Methods: Blood samples from 90 cattle and 101 sheep were used in the study. Glucose concentration was determined in whole blood immediately after blood collection from the jugular vein with the One Touch Vita portable glucometer and in serum with an enzymatic colorimetric method. The agreement between methods was assessed by Passing and Bablok regression analysis. The precision and the accuracy of the measurements were determined using the concordance correlation coefficient. Results: There was a strong linear relationship between the glucose values obtained using the portable glucometer and those obtained by the bench method in both cattle and sheep. Precision was 95% for cattle and 88% for sheep, whereas accuracy was 92% and 99%, respectively. The mean glucose values obtained using the portable glucometer were significantly lower by 8.3% in cattle and 3.2% in sheep than those determined by the bench method. Conclusion: The One Touch Vita portable glucometer can be used in clinical practice to determine blood glucose concentrations in cattle and sheep, but reference intervals (RI) must be corrected to allow for negative bias. Based on these equations the RI for blood glucose in cattle and sheep using the portable glucometer were corrected to 1.84–4.17 and 2.41–4.35 mmol/L, respectively.     

Performance of the Ascensia ENTRUST glucose meter for determination of blood glucose concentration in rats

Background: The Ascensia ENTRUST blood glucose meter is intended for self‐monitoring of blood glucose by diabetic patients. Use of such a glucometer would minimize blood volume requirements for the measurement of glucose in small laboratory animals. Objective: The purpose of this study was to assess the performance of the Ascensia ENTRUST for measuring glucose in whole blood from Wistar rats by evaluating the effect of anticoagulant and sample processing delay and comparing normalized results with plasma glucose concentration. Methods: Blood samples were collected from the retroorbital sinus of 30 male Wistar rats with a wide range of blood glucose concentrations. Glucose concentration was measured with the Ascensia ENTRUST in nonheparinized (NH) and heparinized samples immediately after collection (Hep‐0) and in heparinized samples after a 15 min delay at 23–28°C (Hep‐15). Heparinized samples were centrifuged and glucose concentration was determined in plasma using an automated chemistry analyzer. Results were compared to assess the effect of anticoagulant (NH vs Hep‐0) and time (Hep 0 vs Hep 15), and to compare normalized Hep‐15 results with plasma glucose concentration. Results: Glucose concentration was not significantly different between NH and Hep‐0 samples. Glucose concentration was lower in Hep‐15 (77±36.9 mg/dL) than Hep‐0 (88±39.7 mg/dL) samples, but the difference was not significant. With normalization, Hep‐15 glucose concentration correlated well (r≥.98) with plasma glucose concentration but was lower by 6.0±16.7 mg/dL, with a positive bias at low glucose concentrations and a negative bias at high concentrations. Conclusion: The Ascensia ENTRUST may be adequate for repeated blood glucose measurements in rats, but its results do not accurately predict plasma glucose concentrations measured by an automated clinical chemistry analyzer.     

Accuracy of a continuous glucose monitoring system in dogs and cats with diabetic ketoacidosis

Objective – (1) To determine the ability of a continuous interstitial glucose monitoring system (CGMS) to accurately estimate blood glucose (BG) in dogs and cats with diabetic ketoacidosis. (2) To determine the effect of perfusion, hydration, body condition score, severity of ketosis, and frequency of calibration on the accuracy of the CGMS. Design – Prospective study. Setting – University Teaching Hospital. Animals – Thirteen dogs and 11 cats diagnosed with diabetic ketoacidosis were enrolled in the study within 24 hours of presentation. Interventions – Once BG dropped below 22.2 mmol/L (400 mg/dL), a sterile flexible glucose sensor was placed aseptically in the interstitial space and attached to the continuous glucose monitoring device for estimation of the interstitial glucose every 5 minutes. Measurements and Main Results – BG measurements were taken with a portable BG meter every 2–4 hours at the discretion of the primary clinician and compared with CGMS glucose measurements. The CGMS estimates of BG and BG measured on the glucometer were strongly associated regardless of calibration frequency (calibration every 8 h: r=0.86, P<0.001; calibration every 12 h: r=0.85, P<0.001). Evaluation of this data using both the Clarke and Consensus error grids showed that 96.7% and 99% of the CGMS readings, respectively, were deemed clinically acceptable (Zones A and B errors). Interpatient variability in the accuracy of the CGMS glucose measurements was found but was not associated with body condition, perfusion, or degree of ketosis. A weak association between hydration status of the patient as assessed with the visual analog scale and absolute percent error (Spearman's rank correlation, ρ=?0.079, 95% CI=?0.15 to ?0.01, P=0.03) was found, with the device being more accurate in the more hydrated patients. Conclusions – The CGMS provides clinically accurate estimates of BG in patients with diabetic ketoacidosis.