Performance of glucose dehydrogenase (GDH) based and glucose oxidase (GOX) based blood glucose meter systems at moderately high altitude

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.

The modern pharmacological approach to diabetes: innovative methods of monitoring and insulin treatment

INTRODUCTION

Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterised by a high blood sugar level over a prolonged period of time. In order to maintain this blood glucose value in normal parameters, a careful monitoring of it and insulin administration are necessary.

AREAS COVERED

Thus, to facilitate this procedure, new blood glucose monitoring systems have been studied. The smart lens, the nano tattoo, non-invasive sensors based on reverse ionthophoresis and glucose oxidase - based continuous blood glucose monitoring systems, are the methods described in this study. Of course, not only is blood glucose monitoring important, but also the lifestyle of a drug or the way a drug is administered, especially in the cae of insulin. How insulin is administered is also a topic that we address in this article. In an attempt to promote compliance with the administration, we have discussed about new forms of administering insulin such as: oral, intranasal, administration on the oral mucosa and last but not least, transdermal administration.

EXPERT OPINION

Further, the attention of specialists should be directed to devices based on sensors, with a role in the interruption of insulin administration, in case of detection of hypoglycemia or the additional dose of insulin, if hyperglycemia is detected.

Electrochemical Sensing of Glucose Using Glucose Oxidase/PEDOT:4-Sulfocalix [4]arene/MXene Composite Modified Electrode

Glucose is one of the most important monosaccharides found in the food, as a part of more complex structures, which is a primary energy source for the brain and body. Thus, the monitoring of glucose concentration is more important in food and biological samples in order to maintain a healthy lifestyle. Herein, an electrochemical glucose biosensor was fabricated by immobilization of glucose oxidase (GOX) onto poly(3,4-ethylenedioxythiophene):4-sulfocalix [4]arene (PEDOT:SCX)/MXene modified electrode. For this purpose, firstly, PEDOT was synthesized in the presence of SCX (counterion) by the chemical oxidative method. Secondly, MXene (a 2D layered material) was synthesized by using a high-temperature furnace under a nitrogen atmosphere. After that, PEDOT:SCX/MXene (1:1) dispersion was prepared by ultrasonication which was later utilized to prepare PEDOT:SCX/MXene hybrid film. A successful formation of PEDOT:SCX/MXene film was confirmed by HR-SEM, Fourier transform infrared (FT-IR), and Raman spectroscopies. Due to the biocompatibility nature, successful immobilization of GOX was carried out onto chitosan modified PEDOT:SCX/MXene/GCE. Moreover, the electrochemical properties of PEDOT:SCX/MXene/GOX/GCE was studied through cyclic voltammetry and amperometry methods. Interestingly, a stable redox peak of FAD-GOX was observed at a formal potential of –0.435 V on PEDOT:SCX/MXene/GOX/GCE which indicated a direct electron transfer between the enzyme and the electrode surface. PEDOT:SCX/MXene/GOX/GCE also exhibited a linear response against glucose concentrations in the linear range from 0.5 to 8 mM. The effect of pH, sensors reproducibility, and repeatability of the PEDOT:SCX/MXene/GOX/GCE sensor were studied. Finally, this new biosensor was successfully applied to detect glucose in commercial fruit juice sample with satisfactory recovery.

One-step selective affinity purification and immobilization of His-tagged enzyme by recyclable magnetic nanoparticles

The NiFe2O4 magnetic nanoparticles (NF-MNPs) were prepared for one-step selective affinity purification and immobilization of His-tagged recombinant glucose dehydrogenase (GluDH). The prepared nanoparticles were characterized by a Fourier-transform infrared spectrophotometer and microscopy. The immobilization and purification of His-tagged GluDH on NF-MNPs were investigated. The optimal immobilization conditions were obtained that mixed cell lysis and carriers in a ratio of 0.13 in pH 8.0 Tris-HCl buffer at 30℃ and incubated for 2 h. The highest activity recovery and protein bindings were 71.39% and 38.50 μg mg-1 support, respectively. The immobilized GluDH exhibited high thermostability, pH-stability and it can retain more than 65% of the initial enzyme after 10 cycles for the conversion of glucose to gluconolactone. Comparing with a commercial Ni-NTA resin, the NF-MNPs displayed a higher specific affinity with His-tagged recombinant GluDH.

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.

Diabetes-Related Knowledge of Polish National Mountain Leaders

Nabrdalik, Katarzyna, Hanna Kwiendacz, Monika Gubała, Kinga Tyrała, Mariusz Seweryn, Andrzej Tomasik, Tomasz Sawczyn, Michał Kukla, Władysław Grzeszczak, and Janusz Gumprecht. Diabetes-related knowledge of Polish national mountain leaders. High Alt Med Biol. 19:237-243, 2018.-Mountain trekking is a popular activity for patients with diabetes. In Poland, mountain leaders often accompany organized groups to ensure their safety during treks; we aimed to evaluate their competency in caring for diabetic clients by assessing their diabetes-related knowledge. This was a cross-sectional study among Polish, certified, active mountain leaders carried out by means of an anonymous, standardized 41-item questionnaire adapted from a study by Wee et al. It was distributed through e-mail to 500 leaders. A total of 106 (21.2%) mountain leaders completed the questionnaire (males 60.4%) with a mean (standard deviation [SD]) age of 38.6 (13.5) years. Their mean (SD) length of experience acting as a mountain leader was 11.9 (10.2) years. The average score was 72.4% of the maximum possible (29.7 of 41 points). Results varied significantly depending on gender (p = 0.006). The percentage of correct answers among questions in each section varied between 23.6% and 100%. The main sources of diabetes-related knowledge identified by respondents were members of their family and their friends who suffer from diabetes (33%). First aid courses were indicated as sources of information by only 12.6% of the informants. Results of the questionnaire revealed that respondents did have a reasonable level of diabetes-related knowledge. There were topics in which the respondents achieved lower than an average score, demonstrating a need for further education.

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.

Increased levels of serum γ-glutamyltransferase and uric acid on metabolic, hepatic and kidney parameters in subjects at high altitudes

BACKGROUND

Currently there are no studies on γ-glutamyltransferase (γGT) levels at high altitude or on the relationship between γGT, uric acid and several dysfunctions. The aim of the study was to determine the association between serum γGT and uric acid levels in subjects at high altitude with hemoglobin, glycemia, and lipidic, hepatic and kidney markers.

METHODS

The present study was performed in 487 subjects aged 30-75 years living at 4100 m of altitude. A venous blood sample was drawn from each subject to measure hemoglobin, glucose, and lipid levels and markers of liver and kidney function. Quartiles for serum γGT and uric acid were calculated and associated with different physiological variables. A p-value <0.05 was considered statistically significant.

RESULTS

Serum γGT values were higher in men (38.35± 2.54 IU/L) than in women (30.33±1.76 IU/L) (p<0.01). Similarly, serum uric acid levels were higher in men (5.78± 0.12 mg/dL) than in women (4.29±0.08 mg/dL; p<0.001). Serum γGT levels in the top quartile were associated with higher glycemia, overweight/obesity, increased levels of non-high-density lipoprotein (non-HDL) cholesterol, triglycerides, alanine aminotransferase, alkaline phosphatase, uric acid, creatinine, and hemoglobin. Levels of uric acid in the top quartile were associated with overweight/obesity, elevated non-HDL cholesterol, triglycerides, creatinine, γGT and hemoglobin. Higher arterial blood pressure was associated with high levels of uric acid but not with γGT levels.

CONCLUSIONS

At high altitude, increased γGT levels were associated with hyperglycemia; increased uric acid levels were associated with overweight/obesity, hemoglobin, dyslipidemia, high blood pressure and kidney disease.

Simultaneously improving stability and specificity of cell surface displayed glucose dehydrogenase mutants to construct whole-cell biocatalyst for glucose biosensor application

The improved stability and substrate specificity of cell surface displayed glucose dehydrogenase (GDH) mutants by replacing four amino acids from Bacillus subtilis by using site-directed mutagenesis was systematically investigated. A series of mutated GDHs including E170R/Q252L, V149K/E170R/Q252L, E170R/Q252L/G259A and V149K/E170R/Q252L/G259A, were fused to the ice nucleation protein for displaying on cell surface of Eschericia coli. Q252L/E170R/V149K, Q252L/E170R/G259A and Q252L/E170R/V149K/G259A variants were found stable at a wide pH range and shown excellent thermostability. Especially, the Q252L/E170R/V149K/G259A mutant showed half-life of ~3.8days at 70 °C. Q252L/E170R/V149K/G259A variant exhibited the narrowest substrate specificity for d-glucose. The whole cell displayed GDH mutant could be cultured in a large scale with excellent enzyme activity and productivity. In addition, a sensitive and stable electrochemical glucose biosensor can be prepared using the GDH-mutant bacteria modified electrode. Thus, the whole cell biocatalysts are promising candidates for exploitation in a wide range of industrial applications.

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.

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.

Quality of glucose measurement with blood glucose meters at the point-of-care: relevance of interfering factors

AIM

A good understanding of the relevance of interfering factors having an impact on blood glucose (BG) measurement is needed to obtain the required quality. This depends on the application in which meters designed for self-monitoring of BG (SMBG) are used.

METHODS

By means of a literature search all publications (from January 1, 1980 to August 10, 2009) were identified that report about the influence of potentially interfering substances/factors on the measurement quality of BG meters.

RESULTS

Certain substances (e.g., maltose) can have a profound and misleading impact on the BG measurement result when the enzymatic reaction embedded on the given test strips cross-reacts. Also, a number of other drugs (e.g., acetaminophen) and factors (like temperature and altitude) affect the reliability of BG measurement massively. However, the susceptibility of the BG meter (depending on the enzyme technology of the test strips) differs significantly.

CONCLUSIONS

In daily practice the factors that have a relevant impact on the reliability of BG measurements with modern BG meters are rarely met. Clearly this also depends on the intended use (SMBG in patient hands vs. point-of-care testing in hospitals). To avoid misleading measurement results requires adequate training of all people involved.

Toward an injectable continuous osmotic glucose sensor

BACKGROUND

The growing pandemic of diabetes mellitus places a stringent social and economic burden on the society. A tight glycemic control circumvents the detrimental effects, but the prerogative is the development of new more effective tools capable of longterm tracking of blood glucose (BG) in vivo. Such discontinuous sensor technologies will benefit from an unprecedented marked potential as well as reducing the current life expectancy gap of eight years as part of a therapeutic regime.

METHOD

A sensor technology based on osmotic pressure incorporates a reversible competitive affinity assay performing glucose-specific recognition. An absolute change in particles generates a pressure that is proportional to the glucose concentration. An integrated pressure transducer and components developed from the silicon micro- and nanofabrication industry translate this pressure into BG data.

RESULTS

An in vitro model based on a 3.6 x 8.7 mm large pill-shaped implant is equipped with a nanoporous membrane holding 4-6 nm large pores. The affinity assay offers a dynamic range of 36-720 mg/dl with a resolution of +/-16 mg/dl. An integrated 1 x 1 mm(2) large control chip samples the sensor signals for data processing and transmission back to the reader at a total power consumption of 76 microW.

CONCLUSIONS

Current studies have demonstrated the design, layout, and performance of a prototype osmotic sensor in vitro using an affinity assay solution for up to four weeks. The small physical size conforms to an injectable device, forming the basis of a conceptual monitor that offers a tight glycemic control of BG.

Glucose meters: a review of technical challenges to obtaining accurate results

Glucose meters are universally utilized in the management of hypoglycemic and hyperglycemic disorders in a variety of healthcare settings. Establishing the accuracy of glucose meters, however, is challenging. Glucose meters can only analyze whole blood, and glucose is unstable in whole blood. Technical accuracy is defined as the closeness of agreement between a test result and the true value of that analyte. Truth for glucose is analysis by isotope dilution mass spectrometry, and frozen serum standards analyzed by this method are available from the National Institute of Standards and Technology. Truth for whole blood has not been established, and cells must be separated from the whole blood matrix before analysis by a method like isotope dilution mass spectrometry. Serum cannot be analyzed by glucose meters, and isotope dilution mass spectrometry is not commonly available in most hospitals and diabetes clinics to evaluate glucose meter accuracy. Consensus standards recommend comparing whole blood analysis on a glucose meter against plasma/serum centrifuged from a capillary specimen and analyzed by a clinical laboratory comparative method. Yet capillary samples may not provide sufficient volume to test by both methods, and venous samples may be used as an alternative when differences between venous and capillary blood are considered. There are thus multiple complexities involved in defining technical accuracy and no clear consensus among standards agencies and professional societies on accuracy criteria. Clinicians, however, are more concerned with clinical agreement of the glucose meter with a serum/plasma laboratory result. Acceptance criteria for clinical agreement vary across the range of glucose concentrations and depend on how the result will be used in screening or management of the patient. A variety of factors can affect glucose meter results, including operator technique, environmental exposure, and patient factors, such as medication, oxygen therapy, anemia, hypotension, and other disease states. This article reviews the challenges involved in obtaining accurate glucose meter results.

Thermal stress and point-of-care testing performance: suitability of glucose test strips and blood gas cartridges for disaster response

OBJECTIVE

Point-of-care testing (POCT) devices are deployed in the field for emergency on-site testing under a wide range of environmental conditions. Our objective was to evaluate the performance of glucose meter test strips and handheld blood gas analyzer cartridges following thermal stresses that simulate field conditions.

METHODS

We evaluated electrochemical and spectrophotometric glucose meter systems and a handheld blood gas analyzer. Glucose test strips were cold-stressed (-21 degrees C) and heat-stressed (40 degrees C) for up to 4 weeks. Blood gas cartridges were stressed at -21 degrees C, 2 degrees C, and 40 degrees C for up to 72 hours. Test strip and cartridge performance was evaluated using aqueous quality control solutions. Results were compared with those obtained with unstressed POCT strips and cartridges.

RESULTS

Heated glucose test strips and blood gas cartridges yielded elevated results. Frozen test strips and cooled cartridges yielded depressed glucose and blood gas results, respectively. Frozen cartridges failed.

CONCLUSIONS

The performance of glucose test strips and blood gas cartridges was affected adversely by thermal stresses. Heating generated elevated results, and cooling depressed results. Disaster medical assistance teams and emergency medical responders should be aware of these risks. Field POCT devices must be robust to withstand adverse conditions. We recommend that industry produce POCT devices and reagents suitable for disaster medical assistance teams.