Effect of ambient temperature and humidity on performance of blood glucose meters

Investigation of Glucose-Water Mixtures as a Function of Concentration and Temperature by Infrared Spectroscopy

The main aim of the present paper is to characterize the hydration properties of glucose and the hydrogen bond network in glucose-water mixtures. For these purposes, temperature scans on ten concentration values of glucose-water mixtures were performed by means of Fourier Transform InfraRed (FTIR) spectroscopy. More specifically, in order to get this information an analysis of the intramolecular OH stretching mode, investigating the 3000-3700 cm^-1 spectral range, was performed by means of an innovative approach based on the evaluation of the Spectral Distance (SD). The adopted procedure allows evaluating the glucose hydration number as well as characterizing the temperature behavior of the hydrogen bond network in the glucose-water mixtures. The obtained results for the hydration number are in excellent agreement with literature data and suggest the existence of a particular concentration value for which the hydrogen bond network shows a maximum strength.

Reduced frequency of severe hypoglycemia at mild ambient temperatures between 10 and 20 °C: A population-based study under marine west coast climate conditions

AIMS

To determine the association between ambient temperature and severe hypoglycemia.

METHODS

This was a prospective observational study performed in a prehospital setting. Data from the Emergency Medical Service in Hamburg (Germany) and data from the local weather station were evaluated over a 5-year period. Lowess-regression analysis was conducted to assess the relationship between ambient temperature and frequency of severe hypoglycemia. Additionally, three temperature-ranges were defined in order to compare them with each other with regard to frequency of severe hypoglycemia (<10°C vs. 10-20°C vs. >20°C).

RESULTS

In 2592 patients severe hypoglycemia was diagnosed and treated by emergency physicians (T1DM: n=829/32%; T2DM: n=1763/68%). The median age of patients was 64 (57-72 [20-85]) years. Compared to mild temperatures (10-20°C) the frequency of severe hypoglycemia increased significantly at temperatures above 20°C (+18% (95%-CI: [7%; 22%], p=0.007) and below 10°C (+15% (95%-CI: [6%; 24%], p<0.001).

CONCLUSIONS

The results suggest the existence of a "thermal comfort zone" covering a temperature range from 10 to 20°C in which the frequency of severe hypoglycemia was significantly lower than below 10°C and above 20°C.

Obtaining accurate glucose measurements from wild animals under field conditions: comparing a hand held glucometer with a standard laboratory technique in grey seals

Glucose is an important metabolic fuel and circulating levels are tightly regulated in most mammals, but can drop when body fuel reserves become critically low. Glucose is mobilized rapidly from liver and muscle during stress in response to increased circulating cortisol. Blood glucose levels can thus be of value in conservation as an indicator of nutritional status and may be a useful, rapid assessment marker for acute or chronic stress. However, seals show unusual glucose regulation: circulating levels are high and insulin sensitivity is limited. Accurate blood glucose measurement is therefore vital to enable meaningful health and physiological assessments in captive, wild or rehabilitated seals and to explore its utility as a marker of conservation relevance in these animals. Point-of-care devices are simple, portable, relatively cheap and use less blood compared with traditional sampling approaches, making them useful in conservation-related monitoring. We investigated the accuracy of a hand-held glucometer for 'instant' field measurement of blood glucose, compared with blood drawing followed by laboratory testing, in wild grey seals (Halichoerus grypus), a species used as an indicator for Good Environmental Status in European waters. The glucometer showed high precision, but low accuracy, relative to laboratory measurements, and was least accurate at extreme values. It did not provide a reliable alternative to plasma analysis. Poor correlation between methods may be due to suboptimal field conditions, greater and more variable haematocrit, faster erythrocyte settling rate and/or lipaemia in seals. Glucometers must therefore be rigorously tested before use in new species and demographic groups. Sampling, processing and glucose determination methods have major implications for conclusions regarding glucose regulation, and health assessment in seals generally, which is important in species of conservation concern and in development of circulating glucose as a marker of stress or nutritional state for use in management and monitoring.

The Effects of Temperature and Relative Humidity on Point-of-Care Glucose Measurements in Hospital Practice in a Tropical Clinical Setting

BACKGROUND

Hospitals in tropical countries experience conditions that exceed manufacturer temperature and humidity limits for point-of-care (POC) glucose reagents. Our goal was to assess the effects of out-of-limits storage temperature, operating temperature, and operating humidity on POC glucose measurement reliability.

METHODS

Quality control measurements were performed monthly using glucose test strips stored under controlled conditions and in inpatient wards under ambient conditions. Glucose test strips were evaluated in groups organized by operating temperatures of 24-25 (group 1), 28-29 (group 2), and 33-34°C (group 3), and relative humidity (RH) of ≤70 (group A), ~80 (group B), and ~90% (group C).

RESULTS

Glucose results for different storage conditions were inconsistent. Measurements at higher operating temperatures had lower values with mean differences of -2.4 (P < .001) and -36.5 (P < .001) mg/dL (28-29 vs 24-25°C), and -3.6 (P < .001) and -37.4 (P < .001) mg/dL (33-34 vs 24-25°C) for low and high control levels, respectively. Measurements at higher RH had lower values with mean differences of -4.0 (P < .001) and -13.2 (P < .001) mg/dL (~80 vs ≤70% RH), and -5.8 (P < .001) and -16.6 (P < .001) mg/dL (~90 vs ≤70% RH) for low and high levels, respectively.

CONCLUSIONS

High temperature and high RH decreased glucose concentrations for the POC oxidase-based system we evaluated. We recommend that individual hospitals perform stress testing, then determine if maximum absolute differences, which represent highest risk for patients, are clinically significant for decision making by using error grid analysis.

Point-of-Care Glucose and Ketone Monitoring

Early and rapid identification of hypo- and hyperglycemia as well as ketosis is essential for the practicing veterinarian as these conditions can be life threatening and require emergent treatment. Point-of-care testing for both glucose and ketone is available for clinical use and it is important for the veterinarian to understand the limitations and potential sources of error with these tests. This article discusses the devices used to monitor blood glucose including portable blood glucose meters, point-of-care blood gas analyzers and continuous glucose monitoring systems. Ketone monitoring options discussed include the nitroprusside reagent test strips and the 3-β-hydroxybutyrate ketone meter.

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.

Vulnerability of point-of-care test reagents and instruments to environmental stresses: implications for health professionals and developers

Strategic integration of point-of-care (POC) diagnostic tools during crisis response can accelerate triage and improve management of victims. Timely differential diagnosis is essential wherever care is provided to rule out or rule in disease, expedite life-saving treatment, and improve utilization of limited resources. POC testing needs to be accurate in any environment in which it is used. Devices are exposed to potentially adverse storage and operating conditions, such as high/low temperature and humidity during emergencies and field rescues. Therefore, characterizing environmental conditions allows technology developers, operators, and responders to understand the broad operational requirements of test reagents, instruments, and equipment in order to improve the quality and delivery of care in complex emergencies, disasters, and austere environmental settings. This review aims to describe the effects of environmental stress on POC testing performance and its impact on decision-making, to describe how to study the effects, and to summarize ways to mitigate the effects of environmental stresses through good laboratory practice, development of robust reagents, and novel thermal packaging solutions.

Effects of humidity on foil and vial packaging to preserve glucose and lactate test strips for disaster readiness

OBJECTIVE

Efficient emergency and disaster response is challenged by environmental conditions exceeding test reagent storage and operating specifications. We assessed the effectiveness of vial and foil packaging in preserving point-of-care (POC) glucose and lactate test strip performance in humid conditions.

METHODS

Glucose and lactate test strips in both packaging were exposed to mean relative humidity of 97.0 ± 1.1% in an environmental chamber for up to 168 hours. At defined time points, stressed strips were removed and tested in pairs with unstressed strips using whole blood samples spiked to glucose concentrations of 60, 100, and 250 mg/dL (n = 20 paired measurements per level). A Wilcoxon signed rank test was used to compare stressed and unstressed test strip measurements.

RESULTS

Stressed glucose and lactate test strip measurements differed significantly from unstressed strips, and were inconsistent between experimental trials. Median glucose paired difference was as high as 12.5 mg/dL at the high glucose test concentration. Median lactate bias was -0.2 mmol/L. Stressed strips from vial (3) and foil (7) packaging failed to produce results.

CONCLUSIONS

Both packaging designs appeared to protect glucose and lactate test strips for at least 1 week of high humidity stress. Documented strip failures revealed the need for improved manufacturing process.

Dynamic Temperature and Humidity Environmental Profiles: Impact for Future Emergency and Disaster Preparedness and Response

Introduction

During disasters and complex emergencies, environmental conditions can adversely affect the performance of point-of-care (POC) testing. Knowledge of these conditions can help device developers and operators understand the significance of temperature and humidity limits necessary for use of POC devices. First responders will benefit from improved performance for on-site decision making.

Objective

To create dynamic temperature and humidity profiles that can be used to assess the environmental robustness of POC devices, reagents, and other resources (eg, drugs), and thereby, to improve preparedness.

Methods

Surface temperature and humidity data from the National Climatic Data Center (Asheville, North Carolina USA) was obtained, median hourly temperature and humidity were calculated, and then mathematically stretched profiles were created to include extreme highs and lows. Profiles were created for: (1) Banda Aceh, Indonesia at the time of the 2004 Tsunami; (2) New Orleans, Louisiana USA just before and after Hurricane Katrina made landfall in 2005; (3) Springfield, Massachusetts USA for an ambulance call during the month of January 2009; (4) Port-au-Prince, Haiti following the 2010 earthquake; (5) Sendai, Japan for the March 2011 earthquake and tsunami with comparison to the colder month of January 2011; (6) New York, New York USA after Hurricane Sandy made landfall in 2012; and (7) a 24-hour rescue from Hawaii USA to the Marshall Islands. Profiles were validated by randomly selecting 10 days and determining if (1) temperature and humidity points fell inside and (2) daily variations were encompassed. Mean kinetic temperatures (MKT) were also assessed for each profile.

Results

Profiles accurately modeled conditions during emergency and disaster events and enclosed 100% of maximum and minimum temperature and humidity points. Daily variations also were represented well with 88.6% (62/70) of temperature readings and 71.1% (54/70) of relative humidity readings falling within diurnal patterns. Days not represented well primarily had continuously high humidity. Mean kinetic temperature was useful for severity ranking.

Conclusions

Simulating temperature and humidity conditions clearly reveals operational challenges encountered during disasters and emergencies. Understanding of environmental stresses and MKT leads to insights regarding operational robustness necessary for safe and accurate use of POC devices and reagents. Rescue personnel should understand these principles before performing POC testing in adverse environments.

FergusonWJ, LouieRF, TangCS, Paw UKT, KostGJ. Dynamic temperature and humidity environmental profiles: impact for future emergency and disaster preparedness and response. Prehosp Disaster Med. 2014;29(1):1-8.

Effects of dynamic temperature and humidity stresses on point-of-care glucose testing for disaster care

OBJECTIVE

To characterize the performance of glucose meter test strips using simulated dynamic temperature and humidity disaster conditions.

METHODS

Glucose oxidase- and glucose dehydrogenase-based test strips were dynamically stressed for up to 680 hours using an environmental chamber to simulate conditions during Hurricane Katrina. Paired measurements vs control were obtained using 3 aqueous reagent levels for GMS1 and 2 for GMS2.

RESULTS

Stress affected the performance of GMS1 at level 1 (P < .01); and GMS2 at both levels (P < .001), lowering GMS1 results but elevating GMS2 results. Glucose median-paired differences were elevated at both levels on GMS2 after 72 hours. Median-paired differences (stress minus control) were as much as -10 mg/dL (range, -65 to 33) at level 3 with GMS1, with errors as large as 21.9%. Glucose median-paired differences were as high as 5 mg/dL (range, -1 to 10) for level 1 on GMS2, with absolute errors up to 24.4%.

CONCLUSIONS

The duration of dynamic stress affected the performance of both GMS1 and GMS2 glucose test strips. Therefore, proper monitoring, handling, and storage of point-of-care (POC) reagents are needed to ensure their integrity and quality of actionable results, thereby minimizing treatment errors in emergency and disaster settings.

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.

Geoenvironmental diabetology

Many reports have documented the negative health consequences that environmental stressors can have on patients with diabetes. Studies examining the interaction between the environment and a patient with diabetes can be unified under a single discipline termed "geoenvironmental diabetology." Geoenvironmental diabetology is defined more specifically as the study of how geophysical phenomena impact a patient with diabetes, to include effects on metabolic control, ancillary equipment (e.g., glucometers and insulin pumps), medications, supplies, access to care, and influences on the adaptive strategies employed by patients to care for their diabetes under extreme circumstances. Geological events such as natural disasters (e.g., earthquakes) or extreme weather (e.g., heat waves) are examples of stressors that can affect patients with diabetes and that can be included under the heading of geoenvironmental diabetology. As proposed here, geoenvironmental diabetology refers to how events in the physical world affect those with diagnosed diabetes, rather than how environmental factors might trigger development of disease. As the global prevalence of diabetes continues to increase, including in parts of the world that are especially vulnerable to disasters and climate change, further discussion is warranted on how to best prepare for management of diabetes under conditions of extreme geological and weather events and a changing climate. An overview is presented of various studies that have detailed how geoenvironmental phenomena can adversely affect patients with diabetes and concludes with a discussion of requirements for developing strategies for geoenvironmental diabetes management.

Challenges to glycemic measurement in the perioperative and critically ill patient: a review

Accurate monitoring of glucose in the perioperative environment has become increasingly important over the last few years. Because of increased cost, turnaround time, and sample volume, the use of central laboratory devices for glucose measurement has been somewhat supplanted by point-of-care (POC) glucose devices. The trade-off in moving to these POC systems has been a reduction in accuracy, especially in the hypoglycemic range. Furthermore, many of these POC devices were originally developed, marketed, and received Food and Drug Administration regulatory clearance as home use devices for patients with diabetes. Without further review, many of these POC glucose measurement devices have found their way into the hospital environment and are used frequently for measurement during intense insulin therapy, where accurate measurements are critical. This review covers the technology behind glucose measurement and the evidence questioning the use of many POC devices for perioperative glucose management.

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.

Effect of high altitude on blood glucose meter performance

Participation in high-altitude wilderness activities may expose persons to extreme environmental conditions, and for those with diabetes mellitus, euglycemia is important to ensure safe travel. We conducted a field assessment of the precision and accuracy of seven commonly used blood glucose meters while mountaineering on Mount Rainier, located in Washington State (elevation 14,410 ft). At various elevations each climber-subject used the randomly assigned device to measure the glucose level of capillary blood and three different concentrations of standardized control solutions, and a venous sample was also collected for later glucose analysis. Ordinary least squares regression was used to assess the effect of elevation and of other environmental potential covariates on the precision and accuracy of blood glucose meters. Elevation affects glucometer precision (p = 0.08), but becomes less significant (p = 0.21) when adjusted for temperature and relative humidity. The overall effect of elevation was to underestimate glucose levels by approximately 1-2% (unadjusted) for each 1,000 ft gain in elevation. Blood glucose meter accuracy was affected by elevation (p = 0.03), temperature (p < 0.01), and relative humidity (p = 0.04) after adjustment for the other variables. The interaction between elevation and relative humidity had a meaningful but not statistically significant effect on accuracy (p = 0.07). Thus, elevation, temperature, and relative humidity affect blood glucose meter performance, and elevated glucose levels are more greatly underestimated at higher elevations. Further research will help to identify which blood glucose meters are best suited for specific environments.

Quality assurance of point-of-care testing in the Costa del Sol Healthcare Area (Marbella, Spain)

Traditionally, point-of-care testing (POCT) has been used throughout the healthcare system without the involvement of the central laboratory. After an exhaustive study of the situation of these laboratories in the Costa del Sol Healthcare Area, we designed a quality control program for the POCT. This program targeted the tests done at the points of care throughout the hospital and the Primary Healthcare Area (PHA), using the Joint Commission on Accreditation of Healthcare Organisations (JCAHO) standards for waived testing. We developed two programs: hospital-based tests and ambulatory POCT for outpatients in PHA. The hospital-based POCT apparatus was used for gases, glucose, qualitative urinalysis, Helicobacter pylori detection in gastrointestinal biopsies and coagulation tests. Ambulatory POCT was used to detect glucose, qualitative urinalysis and pregnancy tests. The personnel responsible are nursing staff with no continuing training program. There was no explicit quality control program and most of the results were used as screening except for glucose in the neonatal department. Criteria for selection of kits and devices were basically based on ergonomic and economic evaluation. Therefore, we performed an evaluation of precision and accuracy of two glucose meter devices. We implemented the internal and external quality programs (IQC and EQC) for glucose testing. We elaborated a guide of standard proceedings for quantitative and qualitative POCT and created an annual course for nursing staff. The annual evaluation of the indicators showed 96% for degree of compliance with IQC; 54% of nursing staff participated in the training program; 98% of the glucometers were operating; and 88% agreement between central laboratory and POCT. As there is no previous experience in our healthcare system, this represents a promising new area of working with nurses, who show great interest in participating in these new programs.

Assessment of five portable blood glucose meters for use in cats

OBJECTIVE

To evaluate the clinical and analytic accuracy of 5 portable blood glucose meters (PBGM) in cats, with emphasis on the detection of potential sources of error.

ANIMALS

200 cats.

PROCEDURE

Venous blood glucose readings from 5 PBGM were compared with the results of a hexokinase reference method. Agreement among methods was determined by error grid analysis and statistical methods.

RESULTS

A total of 2,975 PBGM readings and 513 reference values were analyzed. The accuracy of the PBGM varied in different glycemic ranges. The largest differences between PBGM readings and reference values were in the high glycemic range; 4 PBGM underestimated and 1 PBGM overestimated the reference values in most instances. In the low and reference glycemic ranges, the absolute differences between PBGM readings and reference values were small. Despite the analytic differences in accuracy, 4 PBGM had 100% and 1 PBGM had 98.7% of readings in the clinically acceptable values of the error grid analysis. Within- and between-day precisions were good for all PBGM. Significant differences were not detected between readings of EDTA and lithium-heparinized blood and fresh blood without anticoagulant. Compared with these blood types, 1 PBGM had significantly different readings with fluoride anticoagulated blood. In blood samples with a low Hct, all PBGM overestimated glucose concentrations. Sample volumes < 3 microl resulted in inaccurate measurements in 3 PBGM.

CONCLUSIONS AND CLINICAL RELEVANCE

Performance varied among the 5 PBGM analyzed; however, all PBGM were deemed acceptable for clinical use in cats.

Evaluation of five portable blood glucose meters for use in dogs

OBJECTIVE

To evaluate clinical and analytical accuracy of 5 portable blood glucose meters (PBGM) used to measure blood glucose concentrations in dogs and to determine potential sources of error.

DESIGN

Prospective study.

ANIMALS

221 dogs.

PROCEDURE

Venous blood samples were obtained, and results of the 5 PBGM were compared with results of a hexokinase reference method. Agreement among methods was determined by use of error grid analysis and statistical methods.

RESULTS

Accuracy of the PBGM varied with glucose concentration of the sample. The largest differences between results of the PBGM and results of the reference method were obtained with samples with high glucose concentrations; 4 PBGM tended to underestimate and 1 PBGM tended to overestimate the true glucose concentration. Absolute differences between results of the PBGM and results of the reference method were small for samples with low glucose concentrations and samples with concentrations in the reference range. None of the PBGM yielded measurements that would result in clinically unacceptable errors. Within-run and between-day precision was good for all PBGM, and results were not affected by use of EDTA or heparin to anticoagulate blood. Readings of the PBGM were significantly higher for blood samples with low Hct than for samples with normal Hct. For 3 PBGM, samples < 3 microliters resulted in inaccurate measurements.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that currently available PBGM are sufficiently accurate for use in clinical practice to determine blood glucose concentrations in dogs.

Important features of blood glucose meters

OBJECTIVE

To provide an overview of several blood glucose meters that will enhance practicing pharmacists' knowledge and understanding of these devices to allow education of the patient with diabetes.

DATA SOURCES

Original and review articles, blood glucose meter package inserts and manuals.

DATA SYNTHESIS

Careful blood glucose control is essential to prevent long-term complications of diabetes. Newer blood glucose meters have a broad variety of features, including small size, extended memory capacity, blood glucose manipulation techniques, and computer downloading capabilities. The decision to choose a blood glucose meter should be based on a number of criteria, including the patient's needs, ease of use, and affordability.

CONCLUSION

Pharmacists must position themselves to differentiate among the numerous blood glucose meters available on the market and make appropriate recommendations based on patient-specific needs.