Showing papers on "Glucose Measurement published in 1999"

Spectroscopic and Clinical Aspects of Noninvasive Glucose Measurements

Abstract: Frequent determination of glucose concentrations in diabetic patients is an important tool for diabetes management. This requires repetitive lancing and finger bleeding. Use of noninvasive (NI) detection techniques offers several advantages, such as the absence of pain and exposure to sharp objects and biohazard materials, the potential for increased frequency of testing, and hence, tighter control of the glucose concentrations, and the potential for a closed-loop system including a monitor and an insulin pump. These potential advantages have led to considerable interest in the commercialization of NI glucose monitoring devices. Review of the scientific, patent, and commercial literature indicates that the spectroscopic basis for NI determination of glucose is not yet well established, and attempts at commercialization may be several steps ahead of our understanding the origin and characteristics of an in vivo glucose-specific or glucose-related signal. Several technologies have potential for leading to viable measuring devices, but most of the data are based on in vitro experimentation. Because of the technical complexity of in vivo glucose measurements, this review aims at discussing the gap between the established need and current technology limitations.

Noninvasive Glucose Monitoring: Comprehensive Clinical Results

Abstract: ContextIntensive diabetes management using frequent blood glucose measurements to guide therapy has been shown to significantly improve short- and long-term outcomes. Development of a device that makes possible frequent, automatic, painless, and accurate measurements of glucose would facilitate intensive management.ObjectiveTo determine the accuracy of the GlucoWatch automatic glucose biographer (Cygnus Inc) compared with that of serial blood glucose measurements.DesignMulticenter comparative study of the GlucoWatch biographer and the HemoCue blood glucose analyzer (Aktiebolaget Leo) performed between August 29 and October 17, 1998. Participants wore up to 2 biographers during the 15-hour study session and performed 2 fingersticks per hour for comparative blood glucose measurements. The biographers were calibrated with a single HemoCue measurement after a 3-hour warm-up period. Diet and insulin were manipulated to produce a broad glycemic range during the study.SettingControlled clinical environment at 2 diabetes centers and 3 contract research organizations in the United States.ParticipantsA total of 92 subjects (mean [SD] age, 42.1 [15.1] years; 59.8% women) with type 1 or 2 diabetes requiring treatment with insulin.Main Outcome MeasuresMean error, mean absolute error, correlation, slope, and intercept using Deming regression, and clinical significance of differences between biographer readings and blood glucose measurements using the Clarke error grid.ResultsResults showed close tracking of blood glucose over a range of 2.2 to 22.2 mmol/L (40-400 mg/dL) for up to 12 hours using a single point calibration. The biographer readings lagged behind serial blood glucose values by a mean of 18 minutes. An analysis of 2167 data pairs shows a linear relationship (r = 0.88; slope = 1.03; intercept = −0.33 mmol/L [−6 mg/dL]) between biographer readings and serial glucose measurements. The mean absolute error between the 2 measurements was 15.6% (mean error [SD], −0.07 [1.82] mmol/L [−1 {33} mg/dL]), and 96.8% of the data fell in the therapeutically relevant regions of the error grid analysis.ConclusionThese results demonstrate close agreement between GlucoWatch biographer readings and blood glucose measurements using repeated fingerstick blood samples. The automatic, frequent, and noninvasive measurements obtained with the biographer provides more information about glucose levels than the current standard of care.

Advances in Photoacoustic Noninvasive Glucose Testing

Abstract: We report here on in vitro and in vivo experiments that are intended to explore the feasibility of photoacoustic spectroscopy as a tool for the noninvasive measurement of blood glucose. The in vivo results from oral glucose tests on eight subjects showed good correlation with clinical measurements but indicated that physiological factors and person-to-person variability are important. In vitro measurements showed that the sensitivity of the glucose measurement is unaffected by the presence of common blood analytes but that there can be substantial shifts in baseline values. The results indicate the need for spectroscopic data to develop algorithms for the detection of glucose in the presence of other analytes.

Extracellular glucose concentrations in the rat hippocampus measured by zero-net-flux: effects of microdialysis flow rate, strain, and age.

Abstract: The concentration of glucose in the brain's extracellular fluid remains controversial, with recent estimates and measurements ranging from 035 to 33 mM In the present experiments, we used the method of zeronet-flux microdialysis to determine glucose concentration in the hippocampal extracellular fluid of awake, freely moving rats In addition, the point of zero-net-flux was measured across variations in flow rate to confirm that the results for glucose measurement were robust to such variations In 3-month-old male Sprague-Dawley rats, the concentration of glucose in the hippocampal extracellular fluid was found to be 100 +/- 005 mM, which did not vary with changes in flow rate Three-month-old and 24-month-old Fischer-344 rats both showed a significantly higher hippocampal extracellular fluid glucose concentration, at 124 +/- 007 and 121 +/- 004 mM, respectively; there was no significant difference between the two age groups The present data demonstrate variation in extracellular brain glucose concentration between rat strains When taken together with previous data showing a striatal extracellular glucose concentration on the order of 05 mM, the data also demonstrate variation in extracellular glucose between brain regions Traditional models of brain glucose transport and distribution, in which extracellular concentration is assumed to be constant, may require revision

Transcutaneous glucose measurement using near-infrared spectroscopy during hypoglycemia.

Abstract: OBJECTIVE: To analyze a transcutaneous near-infrared spectroscopy system as a technique for in vivo noninvasive blood glucose monitoring during euglycemia and hypoglycemia. RESEARCH DESIGN AND METHODS: Ten nondiabetic subjects and two patients with type 1 diabetes were examined in a total of 27 studies. In each study, the subject's plasma glucose was lowered to a hypoglycemia level (approximately 55 mg/dl) followed by recovery to a glycemic level of approximately 115 mg/dl using an intravenous infusion of insulin and 20% dextrose. Plasma glucose levels were determined at 5-min intervals by standard glucose oxidase method and simultaneously by a near-infrared spectroscopic system. The plasma glucose measured by the standard method was used to create a calibration model that could predict glucose levels from the near-infrared spectral data. The two data sets were correlated during the decline and recovery in plasma glucose, within 10 mg/dl plasma glucose ranges, and were examined using the Clarke Error Grid Analysis. RESULTS: Two sets of 1,704 plasma glucose determinations were examined. The near-infrared predictions during the fall and recovery in plasma glucose were highly correlated (r = 0.96 and 0.95, respectively). When analyzed during 10 mg/dl plasma glucose segments, the mean absolute difference between the near-infrared spectroscopy method and the chemometric reference ranged from 3.3 to 4.4 mg/dl in the nondiabetic subjects and from 2.6 to 3.8 mg/dl in the patients with type 1 diabetes. Using the Error Grid Analysis, 97.7% of all the near-infrared predictions were assigned to the A-zone. CONCLUSIONS: Our findings suggest that the near-infrared spectroscopy method can accurately predict plasma glucose levels during euglycemia and hypoglycemia in humans.

Analytical Characterization of Electrochemical Biosensor Test Strips for Measurement of Glucose in Low-Volume Interstitial Fluid Samples

Abstract: Background: Minimally invasive interstitial fluid (ISF) sampling and glucose measurement technologies were integrated into a hand-held device for diabetic glucose monitoring investigations. Methods: Conventional electrochemical test strip technology (Bayer Glucometer Elite®) was adapted to measure glucose in small (0.5–2.0 μL) samples of ISF. Test strip glucose measurements were performed on a commercial potentiostat and were compared to various reference glucose methodologies (YSI 2300 analyzer, microhexokinase procedure, Bayer Glucometer Elite). Characterizations of the integrated ISF sampling-glucose test strip design included accuracy and precision in various sample media (saline, ISF surrogates, diabetic ISF samples), sample volume dependence, test strip sterilization studies (electron beam, γ irradiation), and diabetic ISF sampling and glucose measurements. Results: Glucose measurements were free from significant media effects. Sample volume variations (0.6–3.2 μL) revealed only modest dependence of glucose measurement bias on sample volume (−1.5% per microliter). Sterilization treatments had only a minor impact on glucose response and test strip aging and no significant impact on interferent responses of the glucose test strips. Diabetic subject testing under minimum fasting conditions of at least 2 h with integrated ISF sampling and glucose measurement gave low ISF glucose measurement imprecision (CV, 4%) and mean glucose results that were indistinguishable from reference (microhexokinase) ISF glucose measurements and from capillary blood glucose measurements (Glucometer Elite). Conclusions: Conventional single-use, electrochemical glucose test strip and ISF collection technologies can be readily integrated to provide real-time ISF sampling and glucose measurements for diabetic monitoring applications.

Technical evaluation of five glucose meters with data management capabilities.

Abstract: Technical performance and data management features are prominent criteria in the selection of an appropriate meter for a point-of-care glucose testing program. We evaluated the technical performance of 5 currently available glucose meters with data management capabilities. The performance of all 5 meters was technically equivalent. Linear regression slopes vs the reference method are in the range of 0.94 to 1.02 and indicate correlation more to plasma values than to whole blood values. The percentage of glucose meter results within +/- 15% of the laboratory value was at least 90%; however, the percentage within +/- 10% was 75% to 87% for most meters. Within-day and between-day precision ranged from 2% to 5% coefficient of variation. Evaluation of linearity with glucose-spiked venous specimens demonstrated that the linearity of each meter agreed with the manufacturer's stated range in most cases. Meter glucose values tended to bias negative as the hematocrit increased, an effect that may be more pronounced at higher glucose concentrations. No volume effects were noted between 5 microL and 40 microL. The results suggest that all meters tested will likely satisfy technical performance criteria in a hospital setting and that selection of a system for point-of-care glucose testing will be influenced by the institution's data management requirements.

Screen Printed Cupric-Hexacyanoferrate Modified Carbon Enzyme Electrode for Single-Use Glucose Measurements

Abstract: A highly selective disposable glucose biosensor based on the dispersion of cupric-hexacyanoferrate and glucose oxidase within a screen-printable carbon ink is described. The dispersed metal-hexacyanoferrate catalyst offers a marked decrease of the overvoltage for the reduction of the enzymatically-liberated hydrogen peroxide, and a stable response at physiological pH. Such efficient catalytic activity allows tuning of the detection potential to a region (around – 0.1V) where interfering reactions are negligible. Such operation eliminates the need for an anti-interference membrane barrier, and along with the one-step dispersion of the enzyme and electrocatalyst, greatly simplifies the sensor fabrication. The high selectivity and simplified fabrication hold great promise for thick-film biosensors for testing glucose and other important substrates of other oxidases.

Apparatus and method for noninvasive glucose measurement

Abstract: An apparatus and method for noninvasively measuring blood glucose concentration. The apparatus (10) disclosed uses light pulses directed onto a patient's skin and reflected back from the patient to measure blood glucose. Reflected light is passed through light filters (30) that transmit a narrow bandwidth of light within a range of wavelengths that is absorbed by glucose and then measured. Unreflected light is passed through identical light filters (40) and also measured. The two measurements are then compared and used to calculate the patient's blood glucose concentration.

Polarization-Based Sensing of Glucose Using an Oriented Reference Film

Abstract: We describe a new approach to glucose sensing using polarization measurements in the presence of a stretch-oriented reference film. The method relies on measurement of the polarized emission from the reference film and of a fluorophore which changes intensity in response to glucose. A glucose-sensitive fluorescent signal was provided by the glucose/galactose binding protein from E. coli. This protein was labeled with an environmentally sensitive fluorophore at a single genetically inserted cysteine residue, and displayed decreased fluorescence upon glucose binding. Using the protein and the reference film we observed glucose-sensitive polarization values for micromolar glucose concentrations. This method of polarization-based sensing is generic and can be used for any sensing fluorophore which displays a change in intensity. In principle, one can construct simple and economical devices for this type of glucose measurement. © 1999 Society of Photo-Optical Instrumentation Engineers.

Site-to-Site Variation of Glucose in Interstitial Fluid Samples and Correlation to Venous Plasma Glucose

Abstract: The importance of determining ambient glycemia for patients with diabetes is well known. The Diabetes Control and Complications Trial completed in 1993 clearly indicated the importance of frequent testing of blood glucose for the management and control of the disease (1). The current method used by diabetic patients for self-monitoring of blood glucose involves lancing a fingertip to obtain a blood sample for testing. The inconvenience of dealing with a blood sample as well as the pain involved with obtaining the sample are often mentioned as reasons for noncompliance to routine glucose monitoring by patients with diabetes. To circumvent these limitations, minimally invasive and noninvasive methods for measuring blood glucose are currently being developed and scrutinized by several investigators. The noninvasive strategies generally adopt optical methodologies to “sample” tissue. The minimally invasive strategies generally attempt to sample a body fluid other than blood through skin penetration or by pulling a fluid sample through the skin. Each of the methodologies raises new questions about the clinical relevance of the glucose measurement that might be made on the tissue or fluid sampled. A method for sampling interstitial fluid (ISF) from which glucose can be measured has been developed in our laboratory. Studies have suggested that glucose concentrations in ISF samples collected via this method closely reflect ambient glycemia (2) and that there is not a clinical difference …

Application of the MediSense Precision-G Blood Glucose Testing System in a Neonatal Intensive Care Unit

Abstract: The ability to perform stat glucose testing in support of a neonatal intensive care unit has traditionally depended on transporting the sample to the central laboratory because most point-of-care glucose analyzers cannot accurately test glucose below 2.22 mmol/L (40 mg/dL). In addition, the high hematocrits commonly encountered in newborns and the high bilirubin concentrations often seen in the neonate can cause major problems with glucose measurements in whole blood. Most glucose meters are used for monitoring the diabetic; thus, their accuracy at low glucose concentrations has not been a prime consideration in their design. The …

A reagent strip and a method for measuring glucose concentration in a sample of whole blood

Abstract: A reagent strip and a method for measuring glucose concentration in whole blood has reduced interference of hematocrit with the glucose measurement. When a biological fluid contacts the strip, it causes, in a reagent impregnated in the strip, a color change that is a measure of the glucose concentration in the fluid. However, the color change is also affected by the red blood cell concentration (hematocrit), thereby reducing the accuracy of the glucose measurement. The hematocrit effect is reduced by adding to the reagent an acrylic acid polymer.

Investigation of stress hyperglycaemia in healthy cats

Abstract: ObjectivesThe objectives of this study were 1) to characterise the changes in bloodnglucose concentrations in healthy cats exposed to a short stressor and 2) to explore associations between blood glucose concentration, behavioural indicators of stress, and blood parameters implicated in the production of stress hyperglycaemia.AnimalsTwenty mixed breed, mixed sex cats were used in the study. All cats used in this study were clinically healthy, were not obese, and had normal glucose tolerance test results during a standard IV glucose tolerance test. ProcedureAll cats had two experimental procedures done one week apart: a five minute bath and a standard intravenous glucose tolerance test. Behavioural responses were observed and graded at intervals during both experiments. Blood was also collected through an indwelling jugular catheter for measurement of physiological parameters,including glucose, lactate, insulin, cortisol, glucagon, adrenaline, and noradrenaline.nResults of bath experimentMost behavioural responses occurred during the bath. Only the behavioural responses of struggling and vocalisation occurred with sufficient frequency to be useful indicators of behavioural stress. Glucose concentration increased rapidly and significantly in all test cats in response to bathing. Increase in glucose concentration was greatest during the bath,nwith peak concentration occurring at the end of the bath.nGlucose response was transient in most cats in this study. Over half the cats (12/20) had glucose concentrations that returned to within 2 standard deviations ofnbaseline between 15 and 90 minutes after the bath. However, eight cats had glucose concentrations which did not return to baseline concentration within the 2 hours of thestudy.nThere was a strong relationship between the behavioural response of struggling and elevated concentrations of glucose and lactate. Struggling cats had higher peak blood glucose and lactate concentrations than did the non-struggling cats.nThe greatest increase in lactate concentration occurred during the 5 minute bath when the incidence and severity of struggling was greatest. Change in mean lactatenconcentrations over the experimental interval correlated with change in mean glucose concentrations (r=0.84;pl0.001).Insulin concentration did not change from baseline until 60 minutes after the end of the bath, when concentrations decreased. There was no correlation between changes in insulin concentrations and changes in glucose concentrations (r=0.39;pg0.10).There was no significant correlation between changes in mean glucose concentrations and changes in mean cortisol concentrations (r=0.32; /?g0.10). Glucose concentration decreased after the stressor ended, however cortisolconcentration reached peak values 15 minutes after the cats were returned to theirncages.There was no significant correlation between the change in mean glucosenconcentrations and the change in mean glucagon concentrations (r=0.48; pg0.05).nThere was no significant difference in glucagon concentrations between cats with highnpeak glucose concentration and cats with lower peak glucose concentration innresponse to the bath.Changes in mean glucose concentration correlated with changes in meannnoradrenaline concentration (r=0.84; /?l0.001). However, comparison ofnnoradrenaline concentrations between cats in the high peak glucose group and the lownpeak glucose group showed no difference.Glucose Tolerance Test (IVGTT)All cats used in the study had normal glucose tolerance based on a T1/2 l86nminutes and KgiUCOse g0.59 %/min. during the IVGTT. Lactate, glucagon, adrenaline,nand noradrenaline did not change from baseline. Very few behavioural responsesnoccurred during the IVGTT.Comparison of mean cortisol response between the bath experiment and thenIVGTT showed that cats had a similar cortisol response during both procedures.Clinical ImplicationsThis study clearly demonstrates the association between glucose and lactatenconcentrations, and physical restraint. Cats are very sensitive to handling procedures,nresponding to even mild restraint with increases in glucose and lactate concentrations.nCareful handling techniques that minimise the physical stress associated withnveterinary procedures may reduce the incidence of stress hyperglycaemia in clinicalncases.In this model, blood glucose did not increase above 16 mmol/1, suggesting thatnblood glucose concentration higher than this may not be explained as a response tonstruggling. Lactate may be a useful predictor of stress hyperglycaemia associated withnstruggling. If blood samples collected simultaneously from struggling cats shownincreased lactate concentrations, then the glucose measurement is likely to benincreased by stress hyperglycaemia.