Showing papers on "Glucose Measurement published in 2005"

Reliability of point-of-care testing for glucose measurement in critically ill adults.

Abstract: Background: Glycemic control is increasingly being recognized as a priority in the treatment of critically ill patients. Titration and monitoring of insulin infusions involve frequent blood glucose measurement to achieve target glucose ranges and prevent adverse events related to hypoglycemia. Therefore, it is imperative that bedside glucose testing methods be safe and accurate. Objective: To determine the accuracy and clinical impact of three common methods of bedside point-of-care testing for glucose measurements in critically ill patients receiving insulin infusions. Design: Prospective observational study. Setting: A 21-bed mixed medical/surgical intensive care unit of a tertiary care teaching hospital. Patients: Thirty consecutive critically ill patients who were vasopressor-dependent (n = 10), had significant peripheral edema (n = 10), or were admitted following major surgery (n = 10). Measurements: Findings from three different methods of glucose measurement were compared with central laboratory measurements: (1) glucose meter analysis of capillary blood (finger-stick); (2) glucose meter analysis of arterial blood; and (3) blood gas/chemistry analysis of arterial blood. Patients were enrolled for a maximum of 3 days and had a maximum of nine sets of measurements determined during this time. Results: Clinical agreement with the central laboratory was significantly better with arterial blood analysis (69.9% and 76.5% for glucose meter and blood gas/chemistry analysis, respectively) than with capillary blood analysis (56.8%; p = .039 and .001, respectively). During hypoglycemia, clinical agreement was only 26.3% with capillary blood analysis and 55.6% and 64.9% for glucose meter and blood gas/chemistry analysis of arterial blood (p = .010 and <.001, respectively). Glucose meter analysis of both arterial and capillary blood tended to provide higher glucose values, whereas blood gas/chemistry analysis of arterial blood tended to yield lower glucose values. Conclusions: The magnitude of the differences in the glucose values offered by the four different methods of glucose measurement led to frequent clinical disagreements regarding insulin dose titration in the context of an insulin infusion protocol for aggressive glucose control.

A novel approach to continuous glucose analysis utilizing glycemic variation.

Abstract: Background: Various methodologies have been proposed for analysis of continuous glucose measurements. These methods have mainly focused on the proportion of low or high glucose readings and have not attempted to analyze other dimensions of the data obtained. This study proposes an algorithm for analysis of continuous glucose data including a novel method of assessing glycemic variability. Methods: Mean blood glucose and mean of daily differences (MODD) assessed the degree that the Continuous Glucose Monitoring System (CGMS®, Medtronic MiniMed, Northridge, CA) trace was representative of the 3-month glycemic pattern. Percentages of times in low, normal, and high glucose ranges were used to assess marked glycemic excursion. Continuous overall net glycemic action (CONGA), a novel method developed by the authors, assessed intra-day glycemic variability. These methods were applied to 10 CGMS traces chosen randomly from those completed by children with type 1 diabetes from the Royal Children's Hospital, Melbour...

A critical assessment of algorithms and challenges in the development of a closed-loop artificial pancreas.

Abstract: The development of an artificial pancreas is placed in the context of the history of the field of feedback control systems, beginning with the water clock of ancient Greece, and including a discussion of current efforts in the control of complex systems. The first generation of artificial pancreas devices included two manipulated variables (insulin and glucose infusion) and nonlinear functions of the error (difference between desired and measured glucose concentration) to minimize hyperglycemia while avoiding hypoglycemia. Dynamic lags between insulin infusion and glucose measurement were relatively small for these intravenous-based systems. Advances in continuous glucose sensing, fast-acting insulin analogs, and a mature insulin pump market bring us close to commercial realization of a closed-loop artificial pancreas. Model predictive control is discussed in-depth as an approach that is well suited for a closed-loop artificial pancreas. A major challenge that remains is handling an unknown glucose distur...

Raman spectroscopy for noninvasive glucose measurements.

Abstract: We report the first successful study of the use of Raman spectroscopy for quantitative, noninvasive ("transcutaneous") measurement of blood analytes, using glucose as an example. As an initial evaluation of the ability of Raman spectroscopy to measure glucose transcutaneously, we studied 17 healthy human subjects whose blood glucose levels were elevated over a period of 2-3 h using a standard glucose tolerance test protocol. During the test, 461 Raman spectra were collected transcutaneously along with glucose reference values provided by standard capillary blood analysis. A partial least squares calibration was created from the data from each subject and validated using leave-one-out cross validation. The mean absolute errors for each subject were 7.8% +/- 61.8% (mean +/- std) with R-2 values of 0.83 +/- 0.10. We provide spectral evidence that the glucose spectrum is an important part of the calibrations by analysis of the calibration regression vectors. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Approved IFCC Recommendation on Reporting Results for Blood Glucose (Abbreviated)

Abstract: In current clinical practice, plasma and blood glucose are used interchangeably with a consequent risk of clinical misinterpretation. In human blood, glucose, like water, is distributed between erythrocytes and plasma. The molality of glucose (amount of glucose per unit of water mass) is the same throughout the sample, but the concentration is higher in plasma because the concentration of water and, therefore, glucose is higher in plasma than in erythrocytes. Different devices for the measurement of glucose may detect and report fundamentally different quantities. Different water concentrations in calibrators, plasma, and erythrocyte fluid can explain some of the differences. Results of glucose measurements depend on sample type and on whether methods require sample dilution or use biosensors in undiluted samples. If the results are mixed up or used indiscriminately, the differences may exceed the maximum allowable error of glucose determinations for diagnosing and monitoring diabetes mellitus, and complicate the treatment. The goal of the IFCC Scientific Division Working Group on Selective Electrodes and Point of Care Testing (IFCC-SD, WG-SEPOCT) is to reach a global consensus on reporting results. The document recommends reporting the concentration of glucose in plasma (with the unit mmol/L), irrespective of sample type or measurement technique. A constant factor of 1.11 is used to convert concentration in whole blood to the equivalent concentration in the pertinent plasma. The conversion will provide harmonized results, facilitating the classification and care of patients and leading to fewer therapeutic misjudgments.

Devices, methods, and kits for non-invasive glucose measurement

Abstract: Described are devices, methods, and kits for non-invasively measuring glucose. In general, the devices comprise skin patches for placement on a skin surface and measurement devices for measuring glucose collected in the patches. The patches may include an adhesive material, a collection layer, an interface layer, and a sweat-permeable membrane. The sweat-permeable membrane is configured to act as a barrier to epidermal contaminants and glucose brought to the skin surface via diffusion. In this way, non-correlatable skin surface glucose will not be measured. The patches may further include components to induce a local sweat response. The measurement device typically includes a display, a processor, and a measurement mechanism. The methods typically include the steps of wiping the skin surface with a wipe containing at least one solvent for removing glucose, placing a patch on a skin surface, and measuring glucose collected in the patch. Kits comprising the patch and measurement device are also described.

A surface plasmon resonance system for the measurement of glucose in aqueous solution

Abstract: In this paper, a surface plasmon resonance (SPR) system is proposed as an alternative approach for glucose measurement. The developed SPR system, which is based on wavelength interrogation technique, has a high detection resolution of 8.67×10−6 refractive index unit (RIU), equivalent to 6.23 mg/dL of glucose in water. The experimental results show that the proposed SPR system is capable of measuring the glucose at the concentration levels in physiological ranges, potentially leading to its further development towards a minimal-invasive glucose measurement of interstitial fluid.

Arterial stiffness is related to insulin resistance in nondiabetic hypertensive older adults.

Abstract: Hypertension, diabetes, obesity, and aging are associated with increased arterial stiffness. Both insulin resistance and hyperglycemia may contribute to the development of arterial stiffness. Older nondiabetic hypertensive adults were recruited to test the following hypotheses: (1) insulin resistance is associated with arterial stiffness, and (2) this relationship is independent of glucose tolerance status. Aortic pulse wave velocity (PWV), pulse pressure (PP), insulin sensitivity index (S(I), measured by insulin-assisted frequently sampled iv glucose test), glucose tolerance status, and abdominal fat mass were assessed in 37 older (23 male, 14 female, mean age 69.4 +/- 5.9 yr), nondiabetic, hypertensive adults after a 4-wk antihypertensive medication withdrawal. Both PWV and PP were negatively correlated with S(I) (r = -0.49, P = 0.002, and r = -0.38, P = 0.02, respectively). The mean PWV and PP in those with normal glucose tolerance were not significantly different from those with impaired glucose tolerance (9.8 +/- 2.4 vs. 10.0 +/- 3.1 m/sec, P = 0.79 and 71 +/- 17 vs. 72 +/- 18 mm Hg, P = 0.80, respectively). In multiple regression analysis, PWV and PP remained independently correlated with S(I) (P < 0.05) after adjusting for age, gender, fasting glucose, glucose tolerance status, body mass index, or abdominal fat mass. These results suggest that in hypertensive, nondiabetic, older adults, insulin resistance is associated with arterial stiffness independent of glucose tolerance status.

Eight-point glucose testing versus the continuous glucose monitoring system in evaluation of glycemic control in type 1 diabetes.

Abstract: CONTEXT Advantages/disadvantages of continuous vs. discrete glucose monitoring are not well documented. OBJECTIVE Compare glucose profiles from home meters vs. continuous sensors. DESIGN Randomized clinical trial conducted by the Diabetes Research in Children Network (DirecNet) to assess the utility of the GlucoWatch G2 Biographer. SETTING Home glucose measurements. PATIENTS Two hundred children (age, 7 to < 18 yr) with type 1 diabetes. INTERVENTION At baseline, subjects were asked to wear the continuous glucose monitoring system (CGMS) sensor and perform meter tests at eight prespecified times of the day (eight-point testing) each for 3 d (2 d using both, 1 d eight-point testing only, 1 d CGMS only). Hemoglobin A1c was measured in a central laboratory. MAIN OUTCOME MEASURE Six-month hemoglobin A1c. This analysis looked at baseline glucose profiles/hemoglobin A1c. RESULTS Only 10% of subjects completed full eight-point testing for 3 d, but median CGMS use was 70 h. Mean glucose was lower when measured by the CGMS compared with eight-point testing (183 +/- 37 vs. 188 +/- 41 mg/dl; 10.2 +/- 2.1 vs.10.4 +/- 2.3 mmol/liter; P = 0.009), especially overnight (2400-0400 h; 174 vs. 199 mg/dl; 9.7 vs. 11.1 mmol/liter; P < 0.001). Associations of hemoglobin A1c with mean glucose were similar for eight-point testing [slope 23 mg/dl per 1% (1.3 mmol/liter); correlation 0.40; P < 0.001] and CGMS [slope 19 mg/dl per 1% (1.1 mmol/liter); correlation 0.39; P < 0.001]. Postprandial excursions were lower for eight-point testing vs. CGMS, especially after dinner (mean excursion -17 vs. 63 mg/dl; -1.0 vs. 3.5 mmol/liter; P < 0.001). CONCLUSIONS Both methods gave similar mean glucose profiles and associations with hemoglobin A1c. Advantages of the CGMS were higher density of data and better detection of postprandial peaks. However, the CGMS may overestimate the frequency of low glucose levels, especially overnight.

Effect of hemoglobin concentration variation on the accuracy and precision of glucose analysis using tissue modulated, noninvasive, in vivo Raman spectroscopy of human blood: a small clinical study

Abstract: Tissue modulated Raman spectroscopy was used noninvasively to measure blood glucose concentration in people with type I and type II diabetes with HemoCue fingerstick measurements being used as reference. Including all of the 49 measurements, a Clarke error grid analysis of the noninvasive measurements showed that 72% were A range, i.e., clinically accurate, 20% were B range, i.e., clinically benign, with the remaining 8% of measurements being essentially erroneous, i.e., C, D, or E range. Rejection of 11 outliers gave a correlation coefficient of 0.80, a standard deviation of 22 mg/dL with p<0.0001 for N=38 and places all but one of the measurements in the A and B ranges. The distribution of deviations of the noninvasive glucose measurements from the fingerstick glucose measurements is consistent with the suggestion that there are at least two systematic components in addition to the random noise associated with shot noise, charge coupled device spiking, and human factors. One component is consistent with the known variation of fingerstick glucose concentration measurements from laboratory reference measurements made using plasma or whole blood. A weak but significant correlation between the deviations of noninvasive measurements from fingerstick glucose measurements and the test subject's hemoglobin concentration was also observed.

Optimal timing for postprandial glucose measurement in pregnant women with diabetes and a non-diabetic pregnant population evaluated by the Continuous Glucose Monitoring System (CGMS®)

Abstract: OBJECTIVE Using the Continuous Glucose Monitoring System (CGMS; Medtronic Minimed) for a group of pregnant women with and without glucose intolerance, we attempted to answer the following questions: (1) when does the physiological peak of postprandial glucose occur?; (2) do non-diabetic pregnant women and pregnant women with diabetes have different postprandial glucose profiles?; and (3) what is the optimal time for postprandial glucose measurement rated according to clinical outcome? METHODS We included 53 pregnant women in our study. Based on the criteria of the German Diabetes Association (fasting, 5.0 mmol/L; 1-h, 10.0 mmol/L; 2-h, 8.6 mmol/L) we included 13 women with gestational diabetes, four with type 1 diabetes and 36 non-diabetic pregnant (NDP) women. Gestational and type 1 diabetics were classed as one group: pregnancy complicated by diabetes (PCD). Patients with carbohydrate intolerance underwent dietary counseling in accordance with the recommendations of the American Diabetes Association. Patients received a CGMS for use over 72 h. This was calibrated seven times a day with an Accu-Check. The pre- and postprandial glucose levels were documented at 15-min intervals for 3 h from the beginning of each meal. The postprandial data from the three meals were added. The group was divided according to three clinical outcome parameters: mode of delivery, birth weight percentile, and diabetes-associated complications. RESULTS Statistically significant differences between groups were found for body mass index, fetal birth weight and oral glucose tolerance test. No significant differences were found for age, parity and gestational age, mode of delivery, and diabetes-associated complications. The sensor provided similar numbers of measurements in both groups (278+/-43 vs. 298+/-73, P = 0.507). The postprandial glucose peak was reached after 82+/-18 min in the non-diabetics vs. 74+/-23 min in the PCD group (not significant). Postprandial glucose values were normally slightly higher in PCD (not significant). We added the postprandial glucose values at each time interval for the three meals for each day. For the sum, there was a significant difference between the measurements at 120 min and at 135 min postprandial (P < 0.05). Dividing the group by clinical outcome showed a significant difference between the postprandial time intervals of 75 min and 105 min (P < 0.05). In addition, the time interval was different from 60 min to 135 min for the mode of delivery and birth weight percentile (P < 0.05). CONCLUSION The 120-min interval is too long and has a lower correlation to clinical outcome parameters than earlier measurements. Our findings show that the optimal time for testing is between 45 and 120 min postprandial. Based on our practical experience and dietary recommendations, we would prefer a 60-min interval, because patients can calculate this more easily and can have more freedom to eat the recommended number of snacks.

Glucose measurements with sensors and ultrasound.

Abstract: Accurate monitoring of the blood glucose level in diabetics is essential in preventing complications. Generally, conventional over-the-counter glucose meters require frequent painful finger punctures to obtain samples, which makes a noninvasive method preferable. The purpose of this study was to demonstrate that glucose levels can be measured transdermally with the combination of the low-profile cymbal array and an electrochemical glucose sensor consisting of amperometric electrodes and a novel glucose oxidase hydrogel. Interstitial fluid glucose concentrations can be determined with the electrochemical glucose sensor after the skin is made permeable to glucose by ultrasound (US) (20 kHz) with the thin (< 7 mm) and light (< 22 g) cymbal array. Using this array to deliver insulin into hyperglycemic rats, our previous experiments demonstrated that blood glucose levels would decrease 233.3 mg/dl with 5 min of US exposure. With the sensor and array, our goal was to determine the glucose levels of hyperglycemic rats noninvasively and evaluate the possible bioeffects. A total of 12 anesthetized rats were placed into two groups (US exposure group and control group) and the array (I(SPTP) = 100 mW/cm(2)) with a saline reservoir operating for 20 min was affixed to the abdomen. The array was removed and an electrochemical glucose sensor was placed on the exposed area to determine the glucose concentrations through the skin. Comparison was made using a commercial glucose meter with the blood collected from a jugular vein. The average blood glucose level determined by the sensor was 356.0 +/- 116.6 mg/dl, and the glucose level measured by the commercial glucose meter was 424.8 +/- 59.1 mg/dl. These results supported the use of this novel system consisting of the electrochemical glucose sensor and the cymbal array for glucose monitoring.

Glucose Oxidase Multilayer Modified Microcantilevers for Glucose Measurement

Abstract: We report a novel enzyme-based microcantilever sensor by using layer-by-layer nanoassembly modification. A glucose oxidase (GOx) functionalized microcantilever underwent bending when it was exposed to glucose solutions. The magnitudes of bending were proportional to the concentrations of glucose. The cantilever bending was specific toward glucose, but not to other sugars such as mannose, fructose, or galactose. The flow rate effect on the cantilever bending response is also discussed. The bending mechanism was investigated, and the kinetic and thermodynamic analysis and experimental results showed that the conformational change of GOx and gluconic formation were the origin of cantilever deflection.

Point-of-care testing of HbA1c and blood glucose in a remote Aboriginal Australian community.

Abstract: OBJECTIVES To assess the accuracy of point-of-care (POC) measurements of capillary blood glucose and glycosylated haemoglobin (HbA(1c)) levels in a remote Aboriginal community with high diabetes prevalence. DESIGN Cross-sectional study comparing POC capillary glucose and HbA(1c) results with those from corresponding venous samples measured in a reference laboratory. PARTICIPANTS AND SETTING 152 residents aged 11-76 years (representing 76% of population aged over 11 years) had POC glucose measurement in November 2003; 88 with POC glucose level > or = 5.0 mmol/L, or self-reported diabetes, had POC HbA(1c) and laboratory glucose and HbA(1c) measurements. MAIN OUTCOME MEASURES POC fasting capillary levels of glucose (HemoCue Glucose 201 analyser, Medipac Scientific, Sydney) and HbA(1c) (DCA 2000+ analyser, Bayer Australia, Melbourne); correlation and mean difference between capillary POC and venous blood laboratory measurements of glucose and HbA(1c). RESULTS Mean and median POC capillary glucose levels were 7.99 mmol/L and 6.25 mmol/L, respectively, while mean and median laboratory venous plasma glucose concentrations were 7.63 mmol/L and 5.35 mmol/L. Values for POC capillary HbA(1c) and laboratory HbA(1c) were identical: mean, 7.06%; and median, 6.0%. The correlation coefficient r for POC and laboratory results was 0.98 for glucose and 0.99 for HbA(1c). The mean difference in results was 0.36 mmol/L for glucose (95% CI, 0.13-0.62; limits of agreement [LOA], - 2.07 to 2.79 mmol/L; P = 0.007) and < 0.01% for HbA(1c) (95% CI, - 0.07% to 0.07%; LOA, - 0.66% to 0.66%; P = 0.95), respectively. CONCLUSIONS POC capillary HbA(1c) testing, in particular, offers an accurate, practical, community-friendly way of monitoring diabetes in rural and remote clinical settings. POC capillary glucose results should be confirmed by a laboratory test of venous plasma if the results are likely to significantly influence clinical decisions.

Non-invasive glucose measurement

Abstract: Described are devices, methods, and kits for non-invasively measuring glucose. In general, the devices comprise skin patches for placement on a skin surface and measurement devices for measuring glucose collected in the patches. The patches may include an adhesive material, a collection layer, an interface layer, and a sweat-permeable membrane. The sweat-permeable membrane is configured to act as a barrier to epidermal contaminants and glucose brought to the skin surface via diffusion. In this way, non-correlatable skin surface glucose will not be measured. The patches may further include components to induce a local sweat response. The measurement device typically includes a display, a processor, and a measurement mechanism. The methods typically include the steps of wiping the skin surface with a wipe containing at least one solvent for removing glucose, placing a patch on a skin surface, and measuring glucose collected in the patch. Kits comprising the patch and measurement device are also described.

System and method for estimating the glucose concentration in blood

Abstract: This application relates to glucose monitoring systems for continuously measuring the glucose concentration in a patients blood. The system is adapted to communicate with one or more sensors (10, 20) for transcutaneous insertion into a patient and for producing sensor signals related to the glucose concentration. The system comprises an electronic calculator unit and a display (14) for displaying the measured glucose concentration. The electronic calculator unit further comprises means for calculating an estimate of the uncertainty, i.e. the degree of accuracy of the glucose measurement, and the display is configured for displaying an interval representing said uncertainty (15).

Chance correlation in non-invasive glucose measurement using near-infrared spectroscopy

Abstract: Although the non-invasive glucose measurement technique based on near-infrared (NIR) spectroscopy has been an active research area for over twenty years, a reliable monitoring method has not been established yet. The key problem is that the spectral variations due to glucose concentration are extremely small compared to that from other biological components. In addition, there are also some ambiguous time-dependent physiological processes, which make the explanation of the model more difficult, especially in the universal calibration. Therefore, in order to produce a model that is related to the actual spectral variation of glucose, reproducible measurements and clinical validation experiments that improve the selectivity and signal to noise ratio of glucose measurement are needed. In this paper, chance correlation in spectroscopy analysis is investigated, which is one of the obstacles to achieving successful NIR spectroscopy analysis, especially in in vivo measurement. The reasons for chance correlation in the in vitro and in vivo experiments are analysed. Methods to avoid it are suggested accordingly and verified with the in vitro experiments. We also investigate the chance correlation for the in vivo NIR diffuse reflectance spectroscopy monitoring blood. Results show that there is significant signal variation after glucose is taken, and the potential chance correlation factors including the instrument-related and physiology-related variations during the in vivo experiments do not contribute to the multivariate model for glucose concentration.

Quality Control of SMBG in Clinical Practice

Abstract: We present results of quality control of self-monitored blood glucose (SMBG) performed in diabetes outpatient clinic. The tests included: inspection of glucose meter, blood glucose self-measurement by a patient, glucose measurement by point-of-care analyzer used in a clinic and with the laboratory method. In the study 158 glucose meters were controlled and compared with HemoCue glucose analyzer used in the clinic as the reference. 122 glucose meters readings were also compared with the reference laboratory method. Tested glucose meters included: Accutrend {18}, Glucotrend {59}, Precision QiD {39}, One Touch {26} and Glucocard II {16}. Reference glucose assays were performed using glucose oxidase method on Hitachi 911 analyzer. Glucose concentrations measured by the controlled glucose meters ranged from 36 to 425 mg/dL. The analytical bias of the glucose meters amounted from 2.48% to 8.27%. Correlation coefficient between results obtained by the tested glucose meters and HemoCue analyzer ranged from 0.957 to 0.980 and between glucose meters and laboratory method from 0.955 to 0.985. Passing-Bablok agreement test and Deming regression analysis indicated good concordance of results between all the tested glucose meters and HemoCue analyzer, whereas good agreement with the laboratory method was found for Accutrend, Glucotrend, Precision QiD and One Touch glucose meters. In conclusion, good analytical performance of the employed glucose meters and a bias less than 10% from the reference values were found. Results of this study show the possibility for routine, convenient for the patient quality control of SMBG in an outpatient clinic.

Evaluation of the Glucometer Elite XL device for screening for neonatal hypoglycaemia.

Abstract: To prevent persistent neurodevelopment and physical growth deficits in neonatal care, it is mandatory to determine blood glucose levels as quickly and precisely as possible, preferably using micro-methods. However, most commercially available instruments have not been validated and approved for this purpose. The aim of this study was to validate the Glucometer Elite XL, a newly developed device for point-of-care testing (POCT). In samples from 869 newborn infants, glucose levels were simultaneously measured by the Glucometer Elite XL in whole blood and by an accepted clinical laboratory method in haemolysed blood using the ECA 2000 device. An acceptable method agreement was found between the POCT and the ECA 2000 method (mean difference 0.013 mmol/l, SD 0.69). As determined by regression analysis (Passing-Bablok), the slope was 1.086 with a y-intercept of −0.4 mmol/l ( r =0.959, P <0.05). The differences between measurement pairs of both assays versus the haematocrit were negligible. With a cut-off for hypoglycaemia at 2.6 mmol/l glucose in haemolysed blood, the sensitivity of the POCT device was 0.63 and specificity was 0.98. Raising the cut-off of the Glucometer Elite XL to 3.2 mmol/l, the sensitivity and specificity incremented to 1.0 and 0.89, respectively. Conclusion:The Glucometer Elite XL instrument can be recommended for point-of-care blood glucose measurement in newborn infants if its character as a screening method is taken into account. To compensate deviating results, we advise to shift its cut-off for hypoglycaemia recognition to a safe threshold of 3.2 mmol/l. However, hypoglycaemia has to be confirmed by a valid glucose measurement in the clinical laboratory.

Noninvasive detection of glucose in porcine eyes

Abstract: In this study, we have measured the Raman spectra of near-physiological-level glucose in the aqueous humor of intact, ex vivo porcine eyes. We inject the glucose solutions into the eyes, control the concentration, and measure the Raman spectra using a compact spectroscopic system with a laser excitation wavelength at 785 nm. The reason for using this fiber-based system is to test the feasibility of the Raman method for a practical noninvasive glucose measurement in the future. We believe that a small, portable system like ours may be made sufficiently affordable and convenient for patient use. Our preliminary data also show that the sensitivity of the system is almost adequate, since we can detect the glucose at near-physiological concentrations in the anterior chamber of the eye in the presence of the other eye components.

[Accuracy, utility and complications of continuous glucose monitoring system (CGMS) in pediatric patients with type 1 diabetes].

Abstract: OBJECTIVE To evaluate the accuracy, utility and complications of continuous glucose monitoring system in children and adolescents with type 1 diabetes. METHODS This retrospective study assessed 16 type 1 diabetic patients (16.12+/-4.41 years) submitted to continuous glucose monitoring system (Medtronic; Northridge, CA) for 72 hours. The following parameters were analyzed: mean capillary glucose level and mean glucose value measured by the continuous glucose monitoring system; glucose excursions (continuous glucose monitoring system vs. capillary glucose measurement), postprandial hyperglycemia (NR < 140 mg/dl), nocturnal hypoglycemia, complications (trauma, local infection, disconnection) and therapeutic management after continuous glucose monitoring. A1c levels were measured at the beginning and after 3 months of the study. RESULTS The mean capillary glucose values were 214.3+/-66.5 mg/dl vs. 207.6+/-54.6 mg/dl by continuous glucose monitoring system, with a significant correlation (p = 0.001). The correlation coefficient and mean absolute error were 0.86+/-0.21 and 12.6% of the median, respectively. The continuous glucose monitoring system was significantly more efficient in detecting glucose excursion than fingerstick capillary blood sampling (p = 0.04; W = 74), and postprandial hyperglycemia was identified in 60% of type 1 diabetic patients with a median value of 157 mg/dl (< 140 mg/dl). Nocturnal hypoglycemia was detected in 46.7% of these patients. The evaluation of A1c levels in eight (50%) patients before continuous glucose monitoring and after 3 months showed a significantly lower level of A1c in this population (8.18+/-1.5 vs. 7.28+/-1.3; p = 0.034). The therapeutic management of type 1 diabetes was changed in 100% of patients. No complications were detected in 93.7% of patients. CONCLUSIONS The continuous glucose monitoring system showed to be a very safe, well-tolerated and highly accurate method, with a low complication rate. It is a good method to identify glucose excursion and postprandial hyperglycemia, and to improve metabolic changes in therapeutic strategies, with a significant impact on the A1c levels of pediatric diabetic patients. The efficacy of the continuous glucose monitoring system in detecting hypoglycemia is still unclear in the medical literature.

Salivary Glucose Monitoring

Abstract: The present invention relates to the measurement of carbohydrate in a fluid and uses thereof. Specifically, the invention is directed to the field of glucose measurement in the saliva of a subject. The invention provides devices and mathematical algorithms for the measurement of glucose in a subject.

Experimental and theoretical aspects of glucose measurement using a microcantilever modified by enzyme-containing polyacrylamide.

Abstract: We report a glucose oxidase-containing polyacrylamide hydrogel-coated microcantilever sensor for the measurement of glucose. This enzymatic reaction of glucose results in swelling of the hydrogel due to formation of charged ions (gluconate molecules and protons). The microcantilever undergoes reversible and reproducible bending deflection upon exposure to solutions containing various glucose concentrations due to swelling or shrinking of the hydrogels. The microcantilever deflections increase when the glucose concentrations increase. A theoretical model has been built to correlate volume changes of the gel with microcantilever bending. The calculated data matched with the experimental results very well. Such hydrogel-coated microcantilevers could potentially be used to prepare microcantilever-based chemical and biological sensors when other enzymes are immobilized in the hydrogel.

Polarized Mueller Matrix Analytical Model for Glucose Measurement in Vitro

Abstract: In this study we present a noninvasive and nonradioactive glucose in vitro measurement technique using the Mueller polarization analytical model. The glucose solution and aqueous humor phantoms are illuminated with a He-Ne (632.8 nm) laser. This in vitro study provides a base and reference data for in vivo eye glucose monitoring. The 16 Mueller polarization matrix element images give information about eye absorption and scattering, and changes in polarization patterns to measure glucose concentration. The interior part of the eye (aqueous humor) contains a birefringent scattering medium for glucose measurement. The Mueller matrix polarimetric technique for simultaneous extraction of rotating linear and circular polarized light is discussed theoretically and experimentally implemented. This method requires calculation of the Mueller matrix for different orientations of polarized light through turbid samples. The results are in good agreement with those in the literature.

Raman spectroscopy for noninvasive glucose measurements

Abstract: We report the first successful study of the use of Raman spectroscopy for quantitative, noninvasive (''transcutaneous'') mea- surement of blood analytes, using glucose as an example. As an initial evaluation of the ability of Raman spectroscopy to measure glucose transcutaneously, we studied 17 healthy human subjects whose blood glucose levels were elevated over a period of 2-3 h using a standard glucose tolerance test protocol. During the test, 461 Raman spectra were collected transcutaneously along with glucose reference values provided by standard capillary blood analysis. A partial least squares calibration was created from the data from each subject and validated using leave-one-out cross validation. The mean absolute errors for each subject were 7.8%61.8% (mean6std) with R 2 values of 0.83 60.10. We provide spectral evidence that the glucose spectrum is an important part of the calibrations by analysis of the calibration regres- sion vectors. © 2005 Society of Photo-Optical Instrumentation Engineers.

Method of differentiating between blood and control solutions containing a common analyte

Abstract: Glucose measured in blood samples is distinguished from glucose measured in the control solutions used to test the optical instruments which make such measurements. The control solutions contain a labeling substance recognized by the optical instrument to distinguish glucose measurements made of control solutions from those made of blood samples.