Effect of ambient temperature on analytical and clinical performance of a blood glucose monitoring system: Omnitest Sensor glucose meter

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.

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.

Hypoglycemia at admission is associated with inhospital mortality in Ugandan patients with severe sepsis

OBJECTIVE

Dysglycemia during sepsis is associated with poor outcomes in resource-rich settings. In resource-limited settings, hypoglycemia is often diagnosed clinically without the benefit of laboratory support. We studied the utility of point-of-care glucose monitoring to predict mortality in severely septic patients in Uganda.

DESIGN

Prospective observational study.

SETTING

One national and two regional referral hospitals in Uganda.

PATIENTS

We enrolled 532 patients with sepsis at three hospitals in Uganda. The analysis included 418 patients from the three sites with inhospital mortality data, a documented admission blood glucose concentration, and evidence of organ dysfunction at admission (systolic blood pressure≤100 mm Hg, lactate>4 mmol/L, platelet number<100,000/μL, or altered mental status).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated the association between admission point-of-care blood glucose concentration and inhospital mortality. We also assessed the accuracy of altered mental status as a predictor of hypoglycemia. Euglycemia occurred in 33.5% (140 of 418) of patients, whereas 16.3% (68 of 418) of patients were hypoglycemic and 50.2% (210 of 418) were hyperglycemic. Univariate Cox regression analyses comparing in-hospital mortality among hypoglycemic (35.3% [24 of 68], hazard ratio 2.0, 95% confidence interval 1.2-3.6, p=.013) and hyperglycemic (29.5% [62 of 210], hazard ratio 1.5, 95% confidence interval 0.96-2.4, p=.08) patients to euglycemic (19.3% [27 of 140]) patients showed statistically significantly higher rates of inhospital mortality for patients with hypoglycemia. Hypoglycemia (adjusted hazard ratio 1.9, 95% confidence interval 1.1-3.3, p=.03) remained significantly and independently associated with inhospital mortality in the multivariate model. The sensitivity and specificity of altered mental status for hypoglycemia were 25% and 86%, respectively.

CONCLUSION

Hypoglycemia is an independent risk factor for inhospital mortality in patients with severe sepsis and cannot be adequately assessed by clinical examination. Correction of hypoglycemia may improve outcomes of critically ill patients in resource-limited 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.

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.

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.

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

OBJECTIVE

Self-monitoring of blood glucose (SMBG) is a fairly efficient method of preventing hypoglycaemia in diabetic patients. Blood glucose meters (BGMs) are influenced by factors such as altitude, temperature, blood oxygen concentration, low atmospheric pressure or humidity. In this study we aimed at evaluating the performance of glucose dehydrogenase (GDH) or glucose oxidase (GOX) based glucometers at moderately high altitude.

METHOD

A total of 286 female or male patients, most of whom had type 2 diabetes, were included in this study. The simultaneous readings made by two different glucometers were compared with the readings made at the reference laboratory.

RESULTS

Blood glucose levels measured by a GDH based glucometer at moderately high altitude were significantly (p=0.007) higher compared to those measured at the reference laboratory. Although blood glucose levels measured by a GOX based glucometer were lower compared to those measured at the reference laboratory, the difference was not significant (p=0.54). The difference between GOX and GDH readings with regard to blood glucose levels was also significant (p=0.001). Blood glucometers were influenced by moderately high altitude.

CONCLUSION

The use of a GOX based glucometer at moderately high altitude may be useful in detecting hypoglycaemia at these conditions, since significantly higher blood glucose levels were measured with a GDH based glucometer compared to reference readings.

Assessing the quality of Bionime self-monitoring blood glucose system Rightest GM110: a critical evaluation of interference and ambient circumstances

BACKGROUND

The key issue in preventing chronic diabetic complications is to maintain near-normoglycemia. Analytical evaluation of Bionime self-monitoring blood glucose (SMBG) Rightest GM110 was carried out in this study.

METHODS

The evaluation was executed according to the Standards for Reporting Diagnostic Accuracy (STARD) and the Clinical and Laboratory Standards Institute (CLSI). The evaluation procedure mainly focused on analytical performance. The accuracy tests included hematocrit, interferants, temperature, humidity, altitude and clinical evaluations.

RESULTS

Good linearity response (R(2)>0.99) and satisfactory precision (CVs: 1.1-2.8%) were observed in glucose concentrations of 0.6-30.5 mmol/l. In hematocrit test, the Rightest GM110 was suitable for use in sample containing hematocrit in the range of 30-55%. Interfering test indicated that almost all substances tested were insignificant, with bias <10% in medium- and hyper-glycemia samples. Satisfactory stability was also found under various ambient circumstances, with bias within +/-10%. In clinical trials, values within the acceptable zone (A+B) were 100% and values within zone A exceed 95% in error grid analysis.

CONCLUSIONS

The Bionime Rightest GM110 is reliable to display accurate glucose concentrations in specimens with irresistible interfering factors.

Using two discrete frequencies within the middle infrared to quantitatively determine glucose in serum

Tight glucose monitoring is essential for the reduction of diabetic complications. This research investigated the changes of absorption spectra observed in serum at three prominent glucose absorption peaks in the middle infrared using a demountable liquid, transmission cell. Two frequencies of light were used to determine the glucose absorption: one at 1193 cm(-1 ) to determine the background water absorption and the other at one of the characteristic peaks (1035, 1080, and 1109 cm(-1)). The peak at 1035 cm(-1) was best for quantitative determination with a standard of error of 20.6 mg/dl (1.1 mmol/L). While interference from other serum constituents could cause problems, urea and albumin-two constituents known to have close absorption peaks-were determined to have no effect on the ability to determine the glucose levels at 1035 cm( -1).