Performance of glucose dehydrogenase-and glucose oxidase-based blood glucose meters at high altitude and low temperature

Effect of short-term exposure to high-altitude hypoxic climate on feed-intake, blood glucose level and physiological responses of native and non-native goat

The exposure to high altitude and cold stress poses challenges in maintaining normal physiological standards and body homeostasis in non-native animals. To enhance our understanding of the physiology of native and non-native goats in high-altitude environments, we conducted a comparative study to examine the impact of natural hypoxic and cold stress conditions on their feed intake (FIT) and associated changes in physiological responses, including plasma glucose concentration (PGC). The study took place at an altitude of 3505.2 m above mean sea level and involved twenty-two healthy females from two different breeds of goats. This study was conducted over a period of 56 days after the arrival of non-native Black Bengal goats (BBN) and compared with native Changthangi (CHAN) goats. Both groups were extensively reared in a natural high-altitude and cold-stress environment in Leh, India, and were subjected to defined housing and management practices. The parameters evaluated included FIT, PGC, respiration rate, heart rate, pulse rate, and rectal temperature. High altitudes had a significant (p < 0.05) impact on FIT, PGC, respiration rate, heart rate, pulse rate, and rectal temperature in BBN, whereas these parameters remained stable in CHAN throughout the study period. Additionally, the detrimental effects of high-altitude stress were more pronounced in non-native goats compared to native goats. These findings suggest that physiological responses in non-native goats tend to stabilize after an initial period of adverse effects in high-altitude environments. Based on the physiological responses and glucose concentration, it is recommended to pay special attention to the nutrition of non-native goats for up to the third week (21 days) after their arrival in high-altitude areas.

Enzyme-functionalized alginate microparticles enable anaerobic culture under ambient oxygen

Methods for culturing oxygen-sensitive cells and organisms under anaerobic conditions are vital to biotechnology research. Here, we report a biomaterial-based platform for anaerobic culture that consists of glucose oxidase (GOX) functionalized alginate microparticles (ALG-GOX), which are designed to deplete dissolved [O2 ] through enzymatic activity. ALG-GOX microparticles were synthesized via a water-in-oil emulsion and had a size of 132.0 ± 51.4 µm. Despite having a low storage modulus, the microparticles remained stable under aqueous conditions due to covalent crosslinking through amide bonds. Enzyme activity was tunable based on the loaded GOX concentration, with a maximum activity of 3.6 ± 0.3 units/mg of microparticles being achieved at an initial loading concentration of 5 mg/mL of GOX in alginate precursor solution. High enzyme activity in ALG-GOX microparticles resulted in rapid oxygen depletion, producing a suitable environment for anaerobic culture. Microparticles loaded with both GOX and catalase (ALG-GOX-CAT) to reduce H2 O2 buildup exhibited sustained activity for potential long-term anaerobic culture. ALG-GOX-CAT microparticles were highly effective for the anaerobic culture of Bacteroides thetaiotaomicron, with 10 mg/mL of ALG-GOX-CAT microparticles supporting the same level of growth in an aerobic environment compared to an anaerobic chamber after 16 h (8.70 ± 0.96 and 10.03 ± 1.03 million CFU, respectively; N.S. p = 0.07). These microparticles could be a valuable tool for research and development in biotechnology.

People With Diabetes Using Insulin Flying Across Multiple Time Zones: Limitations and Opportunities for Diabetes Technologies

Increasingly, people with diabetes (PWD) are using wearable and other devices to support self-management. During air travel, there are 4 stakeholders involved in maximizing the safety of wireless devices for diabetes care used in flight: (1) manufacturers of the devices, (2) airlines, (3) the Transportation Security Administration, and (4) the U.S. Food and Drug Administration. These stakeholders have all developed technologies and policies that assist PWD who prepare for and take appropriate actions during long-haul flights. This article discusses the performance and use of 6 classes of specific wireless diabetes devices during an airplane flight, including the following: (1) blood glucose monitors, (2) continuous glucose monitors, (3) insulin pumps, (4) smart pens for dosing insulin injections, (5) advanced hybrid closed-loop systems, and (6) spinal cord stimulators for painful diabetic neuropathy. Through the policies and safeguards of the 4 stakeholders and the proper self-care measures that insulin-using PWD can take, it is possible to maintain safe glycemic levels on flights across multiple time zones.

UIAA Medical Commission Recommendations for Mountaineers, Hillwalkers, Trekkers, and Rock and Ice Climbers with Diabetes

Hillebrandt, David, Anil Gurtoo, Thomas Kupper, Paul Richards, Volker Schöffl, Pankaj Shah, Rianne van der Spek, Nikki Wallis, and Jim Milledge. UIAA Medical Commission recommendations for mountaineers, hillwalkers, trekkers, and rock and ice climbers with diabetes. High Alt Med Biol. 24: 110-126.-The object of this advice article is not only to give the diabetic mountaineer general guidance but also to inform his or her medical team of practical aspects of care that may not be standard for nonmountaineers. The guidelines are produced in seven sections. The first is an introduction to the guidelines, and the second is an introduction to this medical problem and is designed to be read and understood by diabetic patients and their companions. The third section is for use in an emergency in mountains. The fourth is for rock, ice, and competition climbers operating in a less remote environment. These initial sections are deliberately written in simple language. The fifth and sixth sections are written for clinicians and those with skills to read more technical information, and the seventh looks at modern technology and its pros and cons in diabetes management in a remote area. Sections One and Two could be laminated and carried when in the mountains, giving practical advice.

Point-of-care Glucose Monitoring in COVID-19 Intensive Care Unit: How's It Different?

How to cite this article: Panda R, Hirolli D, Baidya DK. Point-of-care Glucose Monitoring in COVID-19 Intensive Care Unit: How's It Different? Indian J Crit Care Med 2021;25(12):1465-1466.

Comparison of Accu Chek Inform II point-of-care test blood glucose meter with Hexokinase Plasma method for a diabetes mellitus population during surgery under general anesthesia

Purpose

Blood glucose (BG) concentrations of patients with diabetes mellitus (DM) are monitored during surgery to prevent hypo- and hyperglycemia. Access to point-of-care test (POCT) glucose meters at an operating room will usually provide monitoring at shorter intervals and may improve glycemic control. However, these meters are not validated for patients under general anesthesia.

Methods

This cross-sectional study included 75 arterial BG measurements from 75 patients (71 with DM, mostly insulin dependent) who underwent elective non-cardiac surgery under general anesthesia. Arterial blood samples were taken at least 60 minutes after induction. One drop of blood was used for Accu Chek Inform II (ACI II) POCT BG meter and the residual blood was sent to the clinical laboratory for a Hexokinase Plasma reference method. A Bland–Altman plot was used to visualize the differences between both methods, and correlation was assessed using the intra-class correlation coefficient (ICC).

Results

The results showed an estimated mean difference of 0.8 mmol/L between ACI II and the reference method, with limits of agreement equal to -0.6 and 2.2 mmol/L. In general, the reference method produced higher values than ACI II. ICC was 0.955 (95% CI 0.634–0.986), P < 0.001, and concordance correlation coefficient (CCC) was 0.955 (95% CI 0.933–0.970).

Conclusion

Arterial BG measurements during surgery in patients with DM under general anesthesia using POCT BG meter are in general lower than laboratory measurements, but the ICC and CCC show a clinically acceptable correlation. We conclude that POCT measurements conducted on arterial specimens using the ACI II provide sufficiently accurate results for glucose measurement during surgery under general anesthesia.

Evaluation of the Abbot FreeStyle Optium Neo H blood glucose meter in the hyperbaric oxygen environment

INTRODUCTION

This study investigated the effects of hyperbaric oxygen treatment (HBOT) on the accuracy and reliability of point-of-care fingertip capillary blood glucose values in euglycaemic non-diabetic participants compared against venous serum blood glucose samples processed in an accredited pathology laboratory.

METHOD

Ten non-diabetic hyperbaric staff members (age 35-55 years) underwent a standard 243 kPa HBOT exposure for 95 minutes. Blood glucose levels were measured via (i) finger-prick capillary test using the FreeStyle Optium™ Neo H glucometer and (ii) venous serum test using the Cobas 6000 laboratory analyser. Samples were taken at (T1) 0 minutes (pre-HBOT), (T2) 25 minutes, and (T3) 55 minutes into HBOT.

RESULTS

All participants were euglycaemic at T1 (BGL 3.8-5.4 mmol·L⁻¹). The highest venous serum value was 5.90 mmol·L⁻¹ at T3 and the highest capillary value was 6.30 mmol·L⁻¹ at T1. Post hoc tests showed a statistically significant difference between the mean capillary result pre-dive (T1) and readings at T2 (P = 0.001) and T3 (P < 0.001) while differences between T2 and T3 capillary results were not statistically significant, illustrating the effect of HBOT on capillary beds. Differences in venous values across the time points were not significant.

CONCLUSION

Venous serum glucose samples processed in an accredited laboratory may be more consistently accurate, but capillary point-of-care testing avoids delays in sample processing and provides glucose data that are of clinical relevance. The FreeStyle Optium™ Neo H glucometer is safe to use and provides a reliable measurement of blood glucose in the HBOT environment.

Wilderness Medical Society Clinical Practice Guidelines for Diabetes Management

The Wilderness Medical Society convened an expert panel in 2018 to develop a set of evidence-based guidelines for the treatment of type 1 and 2 diabetes, as well as the recognition, prevention, and treatment of complications of diabetes in wilderness athletes. We present a review of the classifications, pathophysiology, and evidence-based guidelines for planning and preventive measures, as well as best practice recommendations for both routine and urgent therapeutic management of diabetes and glycemic complications. These recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks or burdens for each recommendation.

One-shot optimization of multiple enzyme parameters: Tailoring glucose oxidase for pH and electron mediators

Enzymes are biological catalysts with many industrial applications, but natural enzymes are usually unsuitable for industrial processes because they are not optimized for the process conditions. The properties of enzymes can be improved by directed evolution, which involves multiple rounds of mutagenesis and screening. By using mathematical models to predict the structure-activity relationship of an enzyme, and by defining the optimal combination of mutations in silico, we can significantly reduce the number of bench experiments needed, and hence the time and investment required to develop an optimized product. Here, we applied our innovative sequence-activity relationship methodology (innov'SAR) to improve glucose oxidase activity in the presence of different mediators across a range of pH values. Using this machine learning approach, a predictive model was developed and the optimal combination of mutations was determined, leading to a glucose oxidase mutant (P1) with greater specificity for the mediators ferrocene-methanol (12-fold) and nitrosoaniline (8-fold), compared to the wild-type enzyme, and better performance in three pH-adjusted buffers. The k_cat /K_M ratio of P1 increased by up to 121 folds compared to the wild type enzyme at pH 5.5 in the presence of ferrocene methanol.

The Effects of High Altitude on Glucose Homeostasis, Metabolic Control, and Other Diabetes-Related Parameters: From Animal Studies to Real Life

Exposure to high altitude activates several complex and adaptive mechanisms aiming to protect human homeostasis from extreme environmental conditions, such as hypoxia and low temperatures. Short-term exposure is followed by transient hyperglycemia, mainly triggered by the activation of the sympathetic system, whereas long-term exposure results in lower plasma glucose concentrations, mediated by improved insulin sensitivity and augmented peripheral glucose disposal. An inverse relationship between altitude, diabetes, and obesity has been well documented. This is the result of genetic and physiological adaptations principally to hypoxia that favorably affect glucose metabolism; however, the contribution of financial, dietary, and other life-style parameters may also be important. According to existing evidence, people with diabetes are capable of undertaking demanding physical challenges even at extreme altitudes. Still, a number of issues should be taken into account, including the increased physical activity leading to changes in insulin demands and resistance, the performance of measurement systems under extreme weather conditions and the potential deterioration of metabolic control during climbing expeditions. The aim of this review is to present available evidence in the field in a comprehensive way, beginning from the physiology of glucose homeostasis adaptation mechanisms to high altitudes and ending to what real life experience has taught us.

MANAGEMENT OF DIABETES DURING AIR TRAVEL: A SYSTEMATIC LITERATURE REVIEW OF CURRENT RECOMMENDATIONS AND THEIR SUPPORTING EVIDENCE

OBJECTIVE

Individuals with diabetes are increasingly seeking pretravel advice, but updated professional recommendations remain scant. We performed a systematic review on diabetes management during air travel to summarize current recommendations, assess supporting evidence, and identify areas of future research.

METHODS

A systematic review of the English literature on diabetes management during air travel was undertaken utilizing PubMed and MEDLINE. Publications regarding general travel advice; adjustment of insulin and noninsulin therapies; and the use of insulin pumps, glucometers and subcutaneous glucose sensors at altitude were included. Gathered information was used to create an updated summary of glucose-lowering medication adjustment during air travel.

RESULTS

Sixty-one publications were identified, most providing expert opinion and few offering primary data (47 expert opinion, 2 observational studies, 2 case reports, 10 device studies). General travel advice was uniform, with increasing attention to preflight security. Indications for oral antihyperglycemic therapy adjustments varied. There were few recommendations on contemporary agents and on nonhypoglycemic adverse events. There was little consensus on insulin adjustment protocols, many antedating current insulin formulations. Most publications advocated adjusting insulin pump time settings after arrival; however, there was disagreement on timing and rate adjustments. Glucometers and subcutaneous glucose sensors were reported to be less accurate at altitude, but not to an extent that would preclude their clinical use.

CONCLUSION

Recommendations for diabetes management during air travel vary significantly and are mostly based on expert opinion. Data from systematic investigation on glucose-lowering medication adjustment protocols may support the development of a future consensus statement.

ABBREVIATIONS

CSII = continuous subcutaneous insulin infusion (device) DPP-4 = dipeptidyl peptidase 4 EGA = error grid analysis GDH = glucose dehydrogenase GOX = glucose oxidase GLP1 = glucagon-like peptide-1 NPH = neutral protamine Hagedorn SGLT2 = sodium-glucose cotransporter-2.

The real world of blood glucose point-of-care testing (POCT) system running in China teaching hospital

BACKGROUND

 The blood glucose point-of-care testing (POCT) system is important in the decision-making process involving patients suspected of having hypoglycemia. To investigate the real world of the POCT system being used in teaching hospitals in China.

METHODS

The survey was conducted by Hisend Research Group from May 2015 to July 2015 in four teaching hospitals in China. The survey questions were referred to the ISO 15197:2013 standard requirements for the use of the POCT system in a hospital setting.

RESULTS

A total of 170 subjects were included from 4 hospitals, which included nursing staff, nurse unit managers, employees from the department of medical instruments, and staff members employed by the clinical laboratories in the Tianjin Metabolism Hospital, Nanjing First Hospital, First Affiliated Hospital of Dalian Medical University, and the First hospital affiliated with the Xi'an Transportation University. The average score for the four hospitals surveyed in this study was 66.6, which varied from 46.1 to 79.7. The main factors influencing the scores were the multiple choices of blood-glucose meters, and the quality control assessment.

CONCLUSION

Our data indicates that the real world use of the POCT system in hospital settings in China needs more closer adherence to a quality management framework.

Interferences and Limitations in Blood Glucose Self-Testing: An Overview of the Current Knowledge

In general, patients with diabetes performing self-monitoring of blood glucose (SMBG) can strongly rely on the accuracy of measurement results. However, various factors such as application errors, extreme environmental conditions, extreme hematocrit values, or medication interferences may potentially falsify blood glucose readings. Incorrect blood glucose readings may lead to treatment errors, for example, incorrect insulin dosing. Therefore, the diabetes team as well as the patients should be well informed about limitations in blood glucose testing. The aim of this publication is to review the current knowledge on limitations and interferences in blood glucose testing with the perspective of their clinical relevance.

A Comparison Study Between Point-of-Care Testing Systems and Central Laboratory for Determining Blood Glucose in Venous Blood

BACKGROUND

Diabetes mellitus is a metabolic disease that is characterized by hyperglycemia. Blood glucose (BG) is helpful for the diagnosis and treatment of diabetes and an important part of the management of diabetes. Point-of-care testing (POCT) is generally used by patients themselves or medical personnel to monitor BG. The objective of this article was to evaluate the accuracy and consistency of POCT on venous blood samples and compare it with the central laboratory system to determine the reliability of POCT measurement results as diagnostic criteria.

METHOD

A total of 162 venous whole blood samples were pooled in this study, which included different concentrations and were determined by three POCT systems randomly. The results were compared with the central laboratory system, which uses the Glucose GOD-PAP method (HITACHI 7600-120). The accuracy was evaluated by the International Organization for Standardization (ISO) 15197:2013.

RESULT

Bland-Altman and Passing-Bablok regression analysis showed three POCT systems that were comparable with the reference method (0.65, 95% CI: -0.57 to 1.86, Y = -0.11 + 0.95X for ACCU-CHEK^® Performa; 0.40, 95% CI: -1.3 to 2.1, Y = 0.036 + 0.96X for ACCU-CHEK^® Active; 0.70, 95% CI: -0.44 to 1.83, Y = -0.073 + 0.95X for OneTouch ^® UltraVue). According to ISO 15197:2013, all POCT systems showed 100% of the results within 0.83 mmol/l (15 mg/dl) at BG concentrations <5.55 mmol/l (100 mg/dl); 92%, 89.2%, and 95.7% of the measurement results within 15% at BG concentrations ≥5.55 mmol/l (100 mg/dl) for ACCU-CHEK^® Performa, ACCU-CHEK^® Active, and OneTouch^® UltraVue, respectively.

CONCLUSIONS

The POCT system cannot replace the central laboratory system as a provider of a standard result in clinical diagnosis. It can only be used as a screening test.

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.

Cardiometabolic risk factors in native populations living at high altitudes

BACKGROUND

It is generally accepted that metabolic changes that take place in individuals exposed to high elevation are because of ambient hypoxia, which occurs as a consequence of a low total atmospheric pressure. The discovery of hypoxia inducible factor 1 (HIF1), a transcription factor, has been a breakthrough in the understanding of adaption to high altitudes.

OBJECTIVE

The purpose of the present review was to discuss specific epidemiological aspects of cardiovascular disease (CVD) risk factors and their mechanisms in vulnerable, understudied populations living at high altitudes.

RESULTS

Obesity prevalence has been inversely associated with elevation. HIF1 has been related to plasma leptin--a hormone secreted by adipose tissue that produces negative feedback on appetite--and inversely associated with obesity. Diverse factors, such as genetics, chronic hypoxia, diet and lifestyle behaviours, could have an influence on the high dyslipidaemia rates of high-altitude natives. Hypoxia could mediate the effects of altitude on human physiology, including lipid metabolism. Genetic studies suggest that dyslipidaemia could be related to the HIF1. Hypoxia inhibits oxidative phosphorylation and stimulates the oxygen signalling pathway through the HIF1. Low fasting glycaemia in individuals at high altitudes has been shown. An increased GLUT4 protein content in skeletal muscle in response to hypoxia has been reported and could be associated with lower glucose levels. Given the high prevalence of dyslipidaemia and the low prevalence of obesity and diabetes in these impoverished high-altitude communities, changes in lifestyle including decreased physical activity and the consumption of a more westernised diet would likely increase the prevalence of CVD related mortality.

CONCLUSIONS

Control over major CVD risk factors, when identified early, could be the key to reducing morbidity and mortality in patients with limited access to medical services such as Native populations.

Glucose homeostasis during short-term and prolonged exposure to high altitudes

Most of the literature related to high altitude medicine is devoted to the short-term effects of high-altitude exposure on human physiology. However, long-term effects of living at high altitudes may be more important in relation to human disease because more than 400 million people worldwide reside above 1500 m. Interestingly, individuals living at higher altitudes have a lower fasting glycemia and better glucose tolerance compared with those who live near sea level. There is also emerging evidence of the lower prevalence of both obesity and diabetes at higher altitudes. The mechanisms underlying improved glucose control at higher altitudes remain unclear. In this review, we present the most current evidence about glucose homeostasis in residents living above 1500 m and discuss possible mechanisms that could explain the lower fasting glycemia and lower prevalence of obesity and diabetes in this population. Understanding the mechanisms that regulate and maintain the lower fasting glycemia in individuals who live at higher altitudes could lead to new therapeutics for impaired glucose homeostasis.

Physical activity at altitude: challenges for people with diabetes: a review

BACKGROUND

A growing number of subjects with diabetes take part in physical activities at altitude such as skiing, climbing, and trekking. Exercise under conditions of hypobaric hypoxia poses some unique challenges on subjects with diabetes, and the presence of diabetes can complicate safe and successful participation in mountain activities. Among others, altitude can alter glucoregulation. Furthermore, cold temperatures and altitude can complicate accurate reading of glucose monitoring equipment and storage of insulin. These factors potentially lead to dangerous hyperglycemia or hypoglycemia. Over the last years, more information has become available on this subject.

PURPOSE

To provide an up-to-date overview of the pathophysiological changes during physical activity at altitude and the potential problems related to diabetes, including the use of (continuous) blood glucose monitors and insulin pumps. To propose practical recommendations for preparations and travel to altitude for subjects with diabetes.

DATA SOURCES AND SYNTHESIS

We researched PubMed, medical textbooks, and related Internet sites, and extracted human studies and data based on relevance for diabetes, exercise, and altitude.

LIMITATIONS

Given the paucity of controlled trials regarding diabetes and altitude, we composed a narrative review and filled in areas lacking diabetes-specific studies with data obtained from nondiabetic subjects.

CONCLUSIONS

Subjects with diabetes can take part in activities at high, and even extreme, altitude. However, careful assessment of diabetes-related complications, optimal preparation, and adequate knowledge of glycemic regulation at altitude and altitude-related complications is needed.

Impact of partial pressure of oxygen in blood samples on the performance of systems for self-monitoring of blood glucose

BACKGROUND

The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample.

MATERIALS AND METHODS

Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ≤45 mm Hg, approximately 70 mm Hg, and ≥150 mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70 mm Hg, which was considered to be similar to pO2 values in capillary blood samples, and the mean BG value at pO2 levels ≤45 mm Hg and ≥150 mm Hg were calculated.

RESULTS

The GOD systems showed mean relative differences between 11.8% and 44.5% at pO2 values ≤45 mm Hg and between -14.6% and -21.2% at pO2 values ≥150 mm Hg. For the GDH system, the mean relative differences were -0.3% and -0.2% at pO2 values ≤45 mm Hg and ≥150 mm Hg, respectively.

CONCLUSIONS

The magnitude of the pO2 impact on BG measurements seems to vary among the tested oxygen-sensitive GOD systems. The pO2 range in which oxygen-sensitive systems operate well should be provided in the product information.

System accuracy of blood glucose monitoring systems: impact of use by patients and ambient conditions

For self-monitoring of blood glucose by people with diabetes, the reliability of the measured blood glucose values is a prerequisite in order to ensure correct therapeutic decisions. Requirements for system accuracy are defined by the International Organization for Standardization (ISO) in the standard EN ISO 15197:2003. However, even a system with high analytical quality is not a guarantee for accurate and reliable measurement results. Under routine life conditions, blood glucose measurement results are affected by several factors. First, the act of performing measurements as well as the handling of the system may entail numerous possible error sources, such as traces of glucose-containing products on the fingertips, the use of deteriorated test strips, or the incorrect storage of test strips. Second, ambient and sampling conditions such as high altitude, partial pressure of oxygen, ambient temperature, and the use of alternate test sites can have an influence on measurement results. Therefore, the user-friendliness of a system and the quality of the manufacturer's labeling to reduce the risk of handling errors are also important aspects in ensuring reliable and accurate measurement results. In addition, the analytical performance of systems should be less prone to user errors and ambient conditions. Finally, people with diabetes must be aware of the information and instructions in the manufacturer's labeling and must be able to measure and interpret blood glucose results correctly.

In-vitro performance of the Enlite Sensor in various glucose concentrations during hypobaric and hyperbaric conditions

BACKGROUND

There is a need for reliable methods of glucose measurement in different environmental conditions. The objective of this in vitro study was to evaluate the performance of the Enlite® Sensor when connected to either the iPro™ Continuous Glucose Monitor recording device or the Guardian® REAL-Time transmitting device, in hypobaric and hyperbaric conditions.

METHODS

Sixteen sensors connected to eight iPro devices and eight Guardian REAL-Time devices were immersed in three beakers containing separate glucose concentrations: 52, 88, and 207 mg/dl (2.9, 4.9, and 11.3 mmol/liter). Two different pressure tests were conducted: a hypobaric test, corresponding to maximum 18000 ft/5500 m height, and a hyperbaric test, corresponding to maximum 100 ft/30 m depth. The linearity of the sensor signals in the different conditions was evaluated.

RESULTS

The sensors worked continuously, and the sensor signals were collected without interruption at all pressures tested. When comparing the input signals for glucose (ISIGs) and the different glucose concentrations during altered pressure, linearity (R(2)) of 0.98 was found. During the hypobaric test, significant differences (p < .005) were seen when comparing the ISIGs during varying pressure at two of the glucose concentrations (52 and 207 mg/dl), whereas no difference was seen at the 88 mg/dl glucose concentration. During the hyperbaric test, no differences were found.

CONCLUSIONS

The Enlite Sensors connected to either the iPro or the Guardian REAL-Time device provided values continuously. In hyperbaric conditions, no significant differences were seen during changes in ambient pressure; however, during hypobaric conditions, the ISIG was significantly different in the low and high glucose concentrations.

Effects of simulated altitude on blood glucose meter performance: implications for in-flight blood glucose monitoring

BACKGROUND

Most manufacturers of blood glucose monitoring equipment do not give advice regarding the use of their meters and strips onboard aircraft, and some airlines have blood glucose testing equipment in the aircraft cabin medical bag. Previous studies using older blood glucose meters (BGMs) have shown conflicting results on the performance of both glucose oxidase (GOX)- and glucose dehydrogenase (GDH)-based meters at high altitude. The aim of our study was to evaluate the performance of four new-generation BGMs at sea level and at a simulated altitude equivalent to that used in the cabin of commercial aircrafts.

METHODOLOGY/PRINCIPAL FINDINGS

Blood glucose measurements obtained by two GDH and two GOX BGMs at sea level and simulated altitude of 8000 feet in a hypobaric chamber were compared with measurements obtained using a YSI 2300 blood glucose analyzer as a reference method. Spiked venous blood samples of three different glucose levels were used. The accuracy of each meter was determined by calculating percentage error of each meter compared with the YSI reference and was also assessed against standard International Organization for Standardization (ISO) criteria. Clinical accuracy was evaluated using the consensus error grid method. The percentage (standard deviation) error for GDH meters at sea level and altitude was 13.36% (8.83%; for meter 1) and 12.97% (8.03%; for meter 2) with p = .784, and for GOX meters was 5.88% (7.35%; for meter 3) and 7.38% (6.20%; for meter 4) with p = .187. There was variation in the number of time individual meters met the standard ISO criteria ranging from 72-100%. Results from all four meters at both sea level and simulated altitude fell within zones A and B of the consensus error grid, using YSI as the reference.

CONCLUSIONS

Overall, at simulated altitude, no differences were observed between the performance of GDH and GOX meters. Overestimation of blood glucose concentration was seen among individual meters evaluated, but none of the results obtained would have resulted in dangerous failure to detect and treat blood glucose errors or in giving treatment that was actually contradictory to that required.

Effect of ambient temperature on analytical performance of self-monitoring blood glucose systems

BACKGROUND

The analytical quality of self-monitoring of blood glucose (SMBG) can be affected by environmental conditions such as temperature. The objective of this study was to determine the influence of (1) a shift in the ambient temperature immediately before measurement and (2) taking measurements in the lower and upper part of the operating temperature range.

METHODS

Nine different SMBG systems on the Norwegian market were tested with heparinized venous blood (4.8 and 19.0 mmol/L). To test the shift in ambient temperature effect, the glucometer and strips were equilibrated for 1 h at 5°C or 1 h at 30°C before the meter and strips were moved to room temperature, and measurements were performed after 0, 5, 10, 15, and 30 min. To test the lower and upper temperature range, measurements were performed at 10°C and at 39°C after 1 h for temperature equilibration of the glucometer and strips. All these measurements were compared with measurements performed simultaneously on a meter and strips kept at room temperature the whole time.

RESULTS

Six of nine SMBG systems overestimated and/or underestimated the results by more than 5% after moving meters and strips from 5°C or 30°C to room temperature immediately before the measurements. Two systems underestimated the results at 10°C. One system overestimated and another underestimated the results by more than 5% at 39°C.

CONCLUSIONS

The effect on analytical performance was most pronounced after a rapid shift in the ambient temperature. Therefore patients need to wait at least 15 min for temperature equilibration of affected meters and strips before measuring blood glucose.

Wavesense technology glucometer Linus for routine self-monitoring and clinical practice

Conventional glucometer systems for plasma/blood glucose monitoring are based on colorimetry or static electrochemistry using a fixed input signal. The recent glucometer Linus, Wellion, Agamatrix, USA, based on wavesense dynamic electrochemistry, uses a time-varying input signal to give a more accurate glucose reading. The purpose of this study was to compare the plasma glucose (PG) readings obtained by nursing staff from glucometer Linus and PG values estimated on an approved analyzer Daytona™, Randox, Global Medical Instrumentation, Inc., MN, USA. In the course of 5 weeks, 221 fingerprick capillary blood samples were taken from persons with diabetes at different times and investigated using glucometer Linus. Within two following minutes, blood from the same fingerprick was also collected in a tube and centrifuged; the plasma was analyzed on the Daytona™ analyzer. Statistical analysis was performed using the software SPSS v. 15.0, SPSS Inc., Chicago, IL, USA. A total of 221 paired PG values were plotted on the error grid diagram indicating that 218 values (98.6%) of the glucose readings (Linus vs. Daytona) were within the clinically accurate zone A (maximum difference ±20%) and 3 values (1.4%) within the acceptable zone B. Daytona showed 4 PG values <4.2 mmol/l (75 mg/dl) and their difference of respective Linus readings was always <0.83 mmol/l (15 mg/dl). Correlation of results was strong (r = 0.992). Glucometer Linus readings correspond to the ISO and FDA standards. So, Linus appears to be an accurate device for PG-self-monitoring and clinical practice.

New plasma separation glucose oxidase-based glucometer in monitoring of blood with different PO2 levels

BACKGROUND

The PalmLab glucometer is a newly designed plasma separation glucose oxidase (GO)-based glucometer. Past studies have shown that the accuracy of GO-based glucometers is compromised when measurements are taken in patients with high PO(2) levels. We performed a two-arm study comparing the fitness of the PalmLab blood glucometer with that of a standard glucose analyzer in monitoring blood glucose levels in pediatric patients, especially when arterial partial pressure of oxygen (PO(2)) was high.

METHODS

In the first arm of the study, arterial blood samples from pediatric patients were measured by the PalmLab blood glucometer and the YSI 2302 Plus Glucose/Lactate analyzer. In the second arm of the study, venous blood samples from adult volunteers were spiked with glucose water to prepare three different levels of glucose (65, 150, and 300mg/dL) and then oxygenated to six levels of PO(2) (range, 40-400mmHg). The biases of the PalmLab glucometer were calculated.

RESULTS

A total of 162 samples were collected in the first arm of the study. Results of linear regression showed that the coefficient of determination (R(2)) between PalmLab glucometer and standard glucose analyzer was 0.9864. Error grid analysis revealed that all the results were within Zone A (clinically accurate estimate zone). The biases between the two systems were low at different PO(2) levels. In the second arm of the study, the results were also unaffected by changes in PO(2).

CONCLUSION

The PalmLab glucometer provides accurate results in samples with high PO(2) and is suitable for measuring arterial glucose levels in pediatric patients.

Accuracy of handheld blood glucose meters at high altitude

Background

Due to increasing numbers of people with diabetes taking part in extreme sports (e.g., high-altitude trekking), reliable handheld blood glucose meters (BGMs) are necessary. Accurate blood glucose measurement under extreme conditions is paramount for safe recreation at altitude. Prior studies reported bias in blood glucose measurements using different BGMs at high altitude. We hypothesized that glucose-oxidase based BGMs are more influenced by the lower atmospheric oxygen pressure at altitude than glucose dehydrogenase based BGMs.

Methodology/Principal Findings

Glucose measurements at simulated altitude of nine BGMs (six glucose dehydrogenase and three glucose oxidase BGMs) were compared to glucose measurement on a similar BGM at sea level and to a laboratory glucose reference method. Venous blood samples of four different glucose levels were used. Moreover, two glucose oxidase and two glucose dehydrogenase based BGMs were evaluated at different altitudes on Mount Kilimanjaro. Accuracy criteria were set at a bias <15% from reference glucose (when >6.5 mmol/L) and <1 mmol/L from reference glucose (when <6.5 mmol/L). No significant difference was observed between measurements at simulated altitude and sea level for either glucose oxidase based BGMs or glucose dehydrogenase based BGMs as a group phenomenon. Two GDH based BGMs did not meet set performance criteria. Most BGMs are generally overestimating true glucose concentration at high altitude.

Conclusion

At simulated high altitude all tested BGMs, including glucose oxidase based BGMs, did not show influence of low atmospheric oxygen pressure. All BGMs, except for two GDH based BGMs, performed within predefined criteria. At true high altitude one GDH based BGM had best precision and accuracy.

International recommendations for glucose control in adult non diabetic critically ill patients

INTRODUCTION

The purpose of this research is to provide recommendations for the management of glycemic control in critically ill patients.

METHODS

Twenty-one experts issued recommendations related to one of the five pre-defined categories (glucose target, hypoglycemia, carbohydrate intake, monitoring of glycemia, algorithms and protocols), that were scored on a scale to obtain a strong or weak agreement. The GRADE (Grade of Recommendation, Assessment, Development and Evaluation) system was used, with a strong recommendation indicating a clear advantage for an intervention and a weak recommendation indicating that the balance between desirable and undesirable effects of an intervention is not clearly defined.

RESULTS

A glucose target of less than 10 mmol/L is strongly suggested, using intravenous insulin following a standard protocol, when spontaneous food intake is not possible. Definition of the severe hypoglycemia threshold of 2.2 mmol/L is recommended, regardless of the clinical signs. A general, unique amount of glucose (enteral/parenteral) to administer for any patient cannot be suggested. Glucose measurements should be performed on arterial rather than venous or capillary samples, using central lab or blood gas analysers rather than point-of-care glucose readers.

CONCLUSIONS

Thirty recommendations were obtained with a strong (21) and a weak (9) agreement. Among them, only 15 were graded with a high level of quality of evidence, underlying the necessity to continue clinical studies in order to improve the risk-to-benefit ratio of glucose control.

Increases in whole blood glucose measurements using optically based self-monitoring of blood glucose analyzers due to extreme Canadian winters

BACKGROUND

Temperature and humidity have been reported to influence the results of whole blood glucose (WBG) measurements.

METHODS

To determine whether patient WBG values were affected by seasonal variation, we conducted a retrospective analysis of 3 years' worth of weekly averages of patient WBG in five Edmonton hospitals.

RESULTS

In all five hospitals, the winter WBG averages were consistently higher than the summer WBG averages, with the differences varying between 5% and 9%. Whole blood glucose averages were negatively correlated with the outside temperature. This seasonal variation was not observed in weekly patient averages of specimens run in a central hospital laboratory.

INTERPRETATION

It is probable that the seasonal variation of WBG arises from the very low indoor humidities that are associated with external subzero temperatures. These increases in WBG in cold weather may be due to limitations in the WBG measuring systems when operated in decreased humidities and/or increased evaporation of the blood sample during the blood glucose measurement process. The implications of this seasonal variation are significant in that it (1) introduces increased variability in patient WBG, (2) may result in increased glucose-lowering therapy during periods of external cold and low indoor humidity, and (3) confounds evaluations of WBG meter technology in geographic regions of subzero temperature and low indoor humidity. To mitigate the risk of diagnosing and treating factitious hyperglycemia, the humidity of patient care areas must be strictly controlled.

Factors affecting blood glucose monitoring: sources of errors in measurement

Glucose monitoring has become an integral part of diabetes care but has some limitations in accuracy. Accuracy may be limited due to strip manufacturing variances, strip storage, and aging. They may also be due to limitations on the environment such as temperature or altitude or to patient factors such as improper coding, incorrect hand washing, altered hematocrit, or naturally occurring interfering substances. Finally, exogenous interfering substances may contribute errors to the system evaluation of blood glucose. In this review, I discuss the measurement of error in blood glucose, the sources of error, and their mechanism and potential solutions to improve accuracy in the hands of the patient. I also discuss the clinical measurement of system accuracy and methods of judging the suitability of clinical trials and finally some methods of overcoming the inaccuracies. I have included comments about additional information or education that could be done today by manufacturers in the appropriate sections. Areas that require additional work are discussed in the final section.

Self-Monitoring of Blood Glucose (SMBG) in insulin- and non-insulin-using adults with diabetes: consensus recommendations for improving SMBG accuracy, utilization, and research

Current clinical guidelines for diabetes care encourage self-monitoring of blood glucose (SMBG) to improve glycemic control. Specific protocols remain variable, however, particularly among non-insulin-using patients. This is due in part to efficacy studies that neglect to consider (1) the performance of monitoring equipment under real-world conditions, (2) whether or how patients have been taught to take action on test results, and (3) the physiological, behavioral, and social circumstances in which SMBG is carried out. As such, a multidisciplinary group of specialists, including several endocrinologists, a health psychologist, a diabetes nurse practitioner, and a patient advocate (the Panel), discuss within this review article how the potential of SMBG might be fully realized in today's healthcare environment. The resulting recommendations cover technological, clinical, behavioral, and research considerations with the aim of achieving short- and long-term benefits, ranging from fewer hypoglycemic episodes to lower complication-related costs. The panel also made suggestions for designing future studies that increase the ability to discern optimal models of SMBG utilization for individuals with diabetes who may, or may not, use insulin.

Adverse impact of temperature and humidity on blood glucose monitoring reliability: a pilot study

BACKGROUND

The effect of temperature and humidity on the reliability of glucose monitoring systems (GMS) has not been well reported. We performed a study to determine if the effect of temperature and humidity on glucose values could be accurately predicted.

METHODS

Eight GMS, including meter, strips, and glucose control solution (GCS), were placed in an environmental chamber for 50 days. Failure of the environmental chamber allowed for the serendipitous observation of the effect on glucose results of a range of temperature (54-87 degrees F) and humidity (49-100%) typically experienced by patients when performing self-monitoring of blood glucose. GCS was used to generate glucose results in triplicate for each meter daily. Temperature and humidity variations were recorded, and a linear model was generated to explain the variation in glucose results.

RESULTS

Both temperature and humidity had significant effects on the reliability of nearly all GMS. The effect of temperature was greater than the effect of humidity.

CONCLUSIONS

In this pilot study, GMS were unreliable at temperatures and humidity within the manufacturers' recommended limits. Such variations could result in clinically significant errors in diabetes management. Further studies are needed to confirm the potential inadequacies of GMS with multiple meters and real-time patient blood samples. Glucose meter manufacturers should develop systems that either are less affected by climate or adjust reported values based on ambient temperature and humidity.