Blood glucose concentrations of arm and finger during dynamic glucose conditions

We set out to determine the physiological difference between the capillary blood of the arm and finger with the greatest possible accuracy using the HemoCue B-glucose analyzer on subjects undergoing a meal tolerance test (MTT) or oral glucose tolerance test (OGTT). MTT study was performed on 50 subjects who drank a liquid meal (Ensure, 40 g of carbohydrates) and who were tested on the arm and finger every 30 min for up to 4 h. OGTT study was performed on 12 subjects who drank a 100-g glucose solution (Glucola) and were tested on the arm and finger every 15 min during the first hour and thereafter every 30 min for up to 3 h. Average percent glucose difference between arm and finger reached a maximal value about 1 h following glucose load, with arm glucose being about 5% lower than that of finger. At other times, average differences were less than this. At the greatest rate of glucose change (>2 mg/dL-min), mean percent bias was found to be about 6%. Despite these measurable differences, when arm results were plotted on the Clarke error grid against finger values, >97% of the data were within zone A (rest in zone B). Thus, physiological differences between arm and finger were clinically insignificant. Our studies with HemoCue confirmed the existence of measurable physiological glucose differences between arm and finger following a glucose challenge, but these differences were found to be clinically insignificant even in those subjects in whom they were measurable.     

Importance of periodic reeducation of hospital-based nurses in capillary blood glucose monitoring and an evaluation of the usefulness of reflectance meters

Precision and accuracy of capillary blood glucose measurements performed by general staff nurses were assessed before and after a modest reeducation program both with and without the use of reflectance meters. A total of 380 capillary glucose determinations were performed by nurses and the hospital laboratory on the same samples. Prior to reeducation, nurses using meters were more accurate than those reading visually, but no difference was found in precision. Reeducation improved precision equally in both groups while improving accuracy only in the group using meters. While glucose readings with the use of reflectance meters were statistically more accurate than those read visually, the percentage of readings within 10% and 20% of the laboratory readings was the same. Thus, the increased accuracy observed with meters may have little practical significance, suggesting that their use might better be based on other considerations, such as user confidence, convenience, cost, and quality control. Periodic education is, however, an essential component of any quality assurance program.     

Comparison of the accuracy of the HemoCue glucose analyzer with the Yellow Springs Instrument glucose oxidase analyzer, particularly in hypoglycemia

OBJECTIVE: We aimed to assess the accuracy of the HemoCue Beta-glucose analyzer (HemoCue) and its correlation with the Yellow Springs Instrument (YSI 2300 STAT; YSI) glucose oxidase analyzer, in particular for hypoglycemic values. DESIGN AND METHODS: Samples were taken from 24 volunteers during hyperinsulinemic glucose clamp studies. Glucose concentrations were determined immediately with the HemoCue in whole blood and with the YSI in plasma from the same sample. After correction for the difference between whole blood and plasma, the paired plasma glucose concentrations were analyzed with various statistical methods. RESULTS: A total of 500 paired glucose values were obtained, 209 of which were in the hypoglycemic range. Mean+/-s.e. values were 4.85+/-0.004 mmol/l for the HemoCue (range 1.87-16.17) and 4.81+/-0.004 mmol/l for the YSI (range 1.88-15.00; P = 0.80). In the hypoglycemic region, values were 3.26+/-0.004 mmol/l for the HemoCue (range 1.87-5.17) and 3.22+/-0.003 mmol/l for the YSI (range 1.88-4.20; P = 0.59). Regression analyses were HemoCue = 1.019(YSI) -0.0577 mmol/l, with r = 0.9787 for all values; for hypoglycemic values the HemoCue = 1.1169(YSI) -0.3393 mmol/l, with r = 0.8798. Using Altman's residual plot, the difference was 0.03+/-0.0009 mmol/l, with 18 (3.6%) paired values outside the 95% limits of agreement (-0.82 to 0.89 mmol/l). In the hypoglycemic range, the difference was 0.04+/-0.001 mmol/l, with six (2.9%) values outside the 95% limits of agreement (-0.71 to 0.79 mmol/l). In error grid analysis, one value was in zone D (0.2%) and five values (1%) were in zone B; 98.8% were within zone A. CONCLUSIONS: Determination of glucose with the HemoCue system had very good correlation with the YSI system in a broad range of glycemia and also for hypoglycemic values. We believe that these methods can be used interchangeably for research and clinical purposes in adults.     

Evaluation of a new blood glucose monitoring system with auto-calibration for home and hospital bedside use

A new self-calibrating blood glucose monitoring system (BGMS) was evaluated in a series of clinical studies with both ambulatory subjects and with hospitalized patients. The new BGMS requires a 0.6microL sample volume, provides results in 15s, and uses a glucose dehydrogenase chemistry that is oxygen independent. In the first study, Ascensia Contour meters calibrated to whole blood were tested by health care professionals (HCP) and lay users at two clinical sites. Both HCPs and lay users obtained results that fulfilled the ISO 15197:2003 criteria that 95% of self-monitoring blood glucose (SMBG) measurements should fall within +/-20% (for blood glucose (BG) concentrations> or =4.2mmol/L or +/-0.83mmol/L for BG concentrations<4.2mmol/L) of the laboratory value. Lay users and HCPs obtained 97.2 and 96.7% of glucose results within ISO criteria, respectively. In a second study, HCPs assayed blood samples from patients at the hospital bedside using meters calibrated to give whole blood glucose and meters calibrated to give plasma glucose results. Overall, 94.7% of the measurements met the ISO 15197:2003 criteria. Most lay subjects rated the BGMS as either excellent or very good in a questionnaire, and were able to use it properly without training. These findings indicate that this new BGMS is a convenient and accurate instrument system suitable for both hospital bedside use by HCPs and for SMBG by people who routinely monitor their blood glucose.     

A multicenter study of the accuracy of the One Touch Ultra home glucose meter in children with type 1 diabetes

Data are not readily available on the accuracy of one of the most commonly used home blood glucose meters, the One Touch Ultra (LifeScan, Milpitas, California). The purpose of this report is to provide information on the accuracy of this home glucose meter in children with type 1 diabetes. During a 24-h clinical research center stay, the accuracy of the Ultra meter was assessed in 91 children, 3-17 years old, with type 1 diabetes by comparing the Ultra glucose values with concurrent reference serum glucose values measured in a central laboratory. The Pearson correlation between the 2,068 paired Ultra and reference values was 0.97, with the median relative absolute difference being 6%. Ninety-four percent of all Ultra values (96% of venous and 84% of capillary samples) met the proposed International Organisation for Standardisation (ISO) standard for instruments used for self-monitoring of glucose when compared with venous reference values. Ninety-nine percent of values were in zones A + B of the Modified Error Grid. A high degree of accuracy was seen across the full range of glucose values. For 353 data points during an insulin-induced hypoglycemia test, the Ultra meter was found to have accuracy that was comparable to concurrently used benchmark instruments (Beckman, YSI, or i-STAT); 95% and 96% of readings from the Ultra meter and the benchmark instruments met the proposed ISO criteria, respectively. These results confirm that the One Touch Ultra meter provides accurate glucose measurements for both hypoglycemia and hyperglycemia in children with type 1 diabetes.     

Identifying variables associated with inaccurate self-monitoring of blood glucose: proposed guidelines to improve accuracy

PURPOSE: This study was conducted to evaluate patients' proficiency in self-monitoring of blood glucose (SMBG). METHODS: Diabetes nurse educators in 4 suburban Minneapolis clinic sites surveyed the SMBG training/cure practices of 280 patients with type 1 and type 2 diabetes. Participant SMBG technique was measured by direct observation. Participants performed a finger puncture and used their own meters to measure the first blood sample. A second sample was measured on the HemoCue B Glucose analyzer, and a third sample was used to measure hemoglobin. The series of tests were then repeated. If either of the 2 glucose tests was more than 15% from the HemoCue value, participants were reeducated about the manufacturer's suggested procedure. RESULTS: Of the 280 participants, 19% had blood glucose test results greater than the 15% limit for meter accuracy. After reeducation, 69% of those who had initially failed achieved acceptable results. The most significant problems were lack of periodic meter technique evaluation, difficulty using wipe meters, incorrect use of control solutions, lack of hand washing even when observed, and unclean meters. CONCLUSIONS: As a result of the study, guidelines were subsequently developed to evaluate meter accuracy in an outpatient setting. Further effort is needed to establish standards for evaluating SMBG.     

Accuracy of glucose meter use in gestational diabetes

Glucose monitoring is essential for the successful management of gestational diabetes. The accuracy of glucose meters is typically determined over a much wider range of glucose values than that commonly encountered in gestational diabetes. The objective of our study was to look at the accuracy of self-monitoring glucose meters in a clinic setting over a range of glucose values seen in gestational diabetes. We retrospectively analyzed 107 case records of subjects with gestational diabetes, each of whom had three simultaneous laboratory and glucose meter glucose tests. The results were compared using the performance goals that (1) all of glucose meters should have readings within 10% of the reference value and (2) the error grid analysis in the standard format and a modified version suitable for gestational diabetes. We also examined the range of the differences from the reference value. Nearly half of the values (47%) were in excess of 10% of the reference range (either above or below). Close to 15% were in excess of 20% difference from the reference range. Standard error grid analysis showed that 96% of the values fell within sections A of the error grid which are considered acceptable, and 100% fell within sections A and B, differences which are generally considered to have no major impact on care. The modified version of the error grid analysis demonstrated that 39% of the values were outside the acceptable range. Within subjects, a substantial number (26%) had a range of differences that exceeded 20% difference between each other. Although the meters give reasonable results that might be acceptable for general diabetes care, the results provide some cause for concern in the management of gestational diabetes. Given the need for precision in the setting of pregnancy particularly in making the decision of whether to start or withhold insulin therapy, caregivers need to be cognizant of these inaccuracies.     

Accuracy of self-monitoring of blood glucose: impact on diabetes management decisions during pregnancy

PURPOSE: This study tested the hypothesis that the accuracy of self-monitoring of blood glucose (SMBG) values of patients with diabetes during pregnancy deviates substantially from reference values. METHODS: The patients' glucose values were measured on 6 different SMBG meters; reference values were from the HemoCue B Glucose Analyzer. Over a 5-year period, 1973 comparisons between SMBG values and reference values were recorded during clinic visits and used for this study. Data were analyzed for percent of values that varied more than +/- 10.5% and +/- 15.5% from the reference value. Out-of-range data at each variance level were analyzed to determine the impact on medical management if decisions were based solely on SMBG values. RESULTS: One third of SMBG readings deviated significantly, which could adversely affect treatment for half of these patients if diabetes management was based on SMBG values. At the 10.5% deviation level, 34% of SMBG meter readings were out of range; 54% of these would have implied erroneous treatment. At the 15.5% deviation level, 18% were out of range; 63% of these would have implied erroneous management. CONCLUSIONS: The accuracy of home meters should be verified at regular intervals, and SMBG values should not be the sole criterion for diabetes management during pregnancy.     

Accuracy of the hemocue portable glucose analyzer in a large nonhomogeneous population

Several studies have reported inconsistent results between HemoCue (HC) whole blood glucose measurements compared to plasma glucose. We selected a large patient population with diverse pathologies and healthy volunteers to evaluate HC. For this comparison, whole blood glucose concentration was measured using HC and referenced to laboratory plasma glucose. The population (n = 512) included healthy volunteers, diabetics, and patients with heart failure, liver failure, renal failure, renal and liver transplant, and other chronic diseases. Patients were on a wide variety of medications, vitamins, and food supplements. Venous blood samples were collected in tubes containing potassium oxalate and sodium fluoride. Comparison of the results was made using the method of Bland and Altman and ANOVA at three selected glucose ranges. The glucose measurement ([HC + laboratory]/2) ranges were 24-75, 76-129, and 130-404 mg/dL. A positive bias for all three glucose ranges was observed: 38 +/- 17 mg/dL for the high glucose group compared to 24 +/- 9 mg/dL and 22 +/- 10 mg/dL for the middle and low groups, respectively. In the high glucose group 90% of the values were within 10% (R = 0.97) of the laboratory reference values compared to 81% and 55% in the normal and low glucose groups, respectively. HC glucose measurements were generally within two SD from the laboratory plasma reference. HC consistently yielded lower whole blood glucose measurements than plasma with the largest differences seen in the low glucose range (29%). HC measured more consistently at the higher glucose concentrations and was 16% lower than plasma, although the mean absolute error was highest for that range. No significant effects in the bias could be attributed to disease while possible effects from instrument modifications by the manufacturer remain uncertain.     

A comparison of blood glucose meters in Australia

OBJECTIVE: To assess the accuracy and precision of the five currently available blood glucose meters in Australia. DESIGN AND SETTING: Control solutions from manufacturers were used to determine the precision for each meter. Glucose levels in capillary blood samples from 49 patients attending a diabetes clinic were measured with each meter and with a laboratory reference method. OUTCOME MEASURES: The coefficient of variation was calculated to determine precision. Bias, Error Grid analysis, and Bland-Altman plots were used to determine accuracy. RESULTS: The CVs of most meters were acceptable at <5%. Bias ranged from 4.0 to 15.5% with only 1 meter satisfying the American Diabetes Association recommendation of <5% bias. Error Grid analysis showed that 94-100% of readings were clinically accurate, and that none of the differences from the reference method would lead to clinical errors. Bland-Altman plots showed that for two meters the magnitude of the difference between the meter and the reference method increased with increasing glucose values, but did not change significantly with glucose level for the other 3 meters. CONCLUSIONS: Currently available blood glucose meters show acceptable precision, and any errors (with respect to a laboratory method) are highly unlikely to lead to clinical errors. However, only the CareSens meter achieved a bias of less than 5%.     

Effects of simulated altitude on blood glucose meter performance: implications for in-flight blood glucose monitoring

BACKGROUND: Most manufacturers of blood glucose monitoring equipment do not give advice regarding the use of their meters and strips onboard aircraft, and some airlines have blood glucose testing equipment in the aircraft cabin medical bag. Previous studies using older blood glucose meters (BGMs) have shown conflicting results on the performance of both glucose oxidase (GOX)- and glucose dehydrogenase (GDH)-based meters at high altitude. The aim of our study was to evaluate the performance of four new-generation BGMs at sea level and at a simulated altitude equivalent to that used in the cabin of commercial aircrafts. Methodology/Principal Findings: Blood glucose measurements obtained by two GDH and two GOX BGMs at sea level and simulated altitude of 8000 feet in a hypobaric chamber were compared with measurements obtained using a YSI 2300 blood glucose analyzer as a reference method. Spiked venous blood samples of three different glucose levels were used. The accuracy of each meter was determined by calculating percentage error of each meter compared with the YSI reference and was also assessed against standard International Organization for Standardization (ISO) criteria. Clinical accuracy was evaluated using the consensus error grid method. The percentage (standard deviation) error for GDH meters at sea level and altitude was 13.36% (8.83%; for meter 1) and 12.97% (8.03%; for meter 2) with p = .784, and for GOX meters was 5.88% (7.35%; for meter 3) and 7.38% (6.20%; for meter 4) with p = .187. There was variation in the number of time individual meters met the standard ISO criteria ranging from 72-100%. Results from all four meters at both sea level and simulated altitude fell within zones A and B of the consensus error grid, using YSI as the reference. CONCLUSIONS: Overall, at simulated altitude, no differences were observed between the performance of GDH and GOX meters. Overestimation of blood glucose concentration was seen among individual meters evaluated, but none of the results obtained would have resulted in dangerous failure to detect and treat blood glucose errors or in giving treatment that was actually contradictory to that required.     

The validity of the Medisafe self-monitoring blood glucose system

Self-monitoring blood glucose (SMBG) meters are widely used in the management of diabetes. The new SMBG meter Medisafe, which is based on the optoelectric colorimetry method, has been introduced. The objective of this study was to validate the Medisafe SMBG meters in comparison with the reference autoanalyzer (Hitachi 717) and to assess the repeatability of the instrument as well as variations of tip replacement. Samples of capillary and venous blood from 299 patients were tested. The correlation coefficients between the Medisafe-measured capillary and venous blood glucose levels and the reference autoanalyzer venous plasma glucose levels were 0.976 and 0.975, respectively. The range of differences from the reference value was examined; only 4% was in excess of +/- 20% of the reference laboratory value, and more than 40% of the values were within 5% of the reference laboratory value. Moreover, repeatability of the Medisafe capillary blood samples measured in three patients with three different blood glucose levels was determined. The coefficients of variation of blood glucose values are within 5%. In addition, the results of mean and SEM from each replication in three patients and glucose measurement from different lots of tips showed no significant difference (p > 0.05). It is concluded that the Medisafe SMBG meter has shown good results in terms of validity and repeatability. Furthermore, it provides safety from blood contamination, which is recommended in countries with a high prevalence of human immunodeficiency virus.     

A new, improved test system for rapid measurement of blood glucose

Several models of blood glucose meters are available to diabetic patients. They all require several steps for their operation, which increases the potential for user error. A new meter (One Touch TM System, Lifescan Inc., a Johnson & Johnson Company, Mountain View, CA) was designed to minimise the operational steps and therefore increase reliability. This system was compared for precision, accuracy and clinical safety to the Yellow Spring Instrument (YSI) Model 23A Glucose Analyser (Yellow Springs, OH) in 20 diabetic subjects. Good precision was demonstrated by the coefficient of variation (CV%) in 20 tests performed by each subject on a single heparinised specimen of their own venous blood. The CV was 4.5% (range 1.8-10.4). Accuracy was determined by the regression of the mean of the glucose results corrected for glycolysis compared to the mean YSI result. The regression line had a slope of 1.02, a Y intercept at -4.21 mg/dl, a correlation coefficient (r) of 0.999 (P less than 0.001) and a root mean square % (RMS) error of 4.385. Clinical safety was demonstrated by error grid analysis in which 399 of 400 tests fell in the clinically safe range, and reading error analysis in which two of 400 tests fell more than 25% from the reference method. It is concluded that the One Touch system has good accuracy when compared with the YSI method, is easier to use than the presently available meters, and is a useful addition to the management of diabetes in patients who perform self-monitoring of blood glucose.     

Bedside glucose monitoring: in compliance with regulatory standards

When accurately performed, bedside glucose monitoring (BGM) is a prompt, reliable, and cost-effective method of managing patients who require a high degree of glucose control. However, regulatory agencies have criticized the quality-control deficiencies of most existing BGM programs. A new generation of multi-user reflectance meters enables the various regulatory directives to be more easily satisfied. These meters provide computer-assisted quality control analysis and facilitate operator feedback for each control test. New York State Department of Health regulations state that the ultimate responsibility for BGM belongs to the chemistry laboratory director. We believe that nursing personnel should retain their patient care prerogative to perform glucose monitoring. Implementation of our successful BGM program required the collaboration of nursing, medical, laboratory, and administrative personnel. These departments combined theoretical and practical expertise with material and financial management. During the first 5 months of operation, our program has shown a steady increase from 78% to 89% of control tests performed correctly. This model can be used by other hospitals to achieve a successful BGM program.     

Performance evaluation of blood glucose monitoring devices

Many new technologies are being applied to measure blood glucose concentrations, but there is a lack of a standardized approach to evaluate performance of these devices. We sought to identify the key elements in evaluating the performance of devices for measuring blood glucose. We examined these elements in a multicenter study of four brands of glucose meters that are commonly used by diabetic patients. We tested control materials, spiked whole blood specimens, and 461 heparinized whole blood specimens in triplicate by each of the four brand glucose meters, and analyzed the plasma glucose concentrations of these specimens by a hexokinase (HK) method that incorporated reference materials developed by National Institute of Standards and Technology. Testing with glucose meters was performed at three sites, with multiple operators, meters, and representative lots of reagents. We evaluated the systematic bias, random error, and clinical significance of glucose meters. Meters were precise with a coefficient of variation of <4% across a wide range of glucose concentrations. Slopes significantly different from 1.0 were observed for two meters with 11-13% and -11% to -13% at the 95% confidence interval level by the linear regression of meter results versus the HK method from 33 to 481 mg/dL (correlation coefficient >0.98 and standard error of estimation S(y/x) <13 mg/dL for both meters). Analysis of the clinical significance of bias by Clarke Error Grid showed that results of the four meters were outside the accurate zone (26.5%, 2.4%, 1.5%, and 5.6%). Only a small number of the results showed clinically significant bias, mostly in the hypoglycemic range. Meters performed consistently throughout the study and, generally, were precise, although precision varied at extremely high or low glucose concentrations. Two of the glucose meters had substantial systematic bias when compared with an HK method, indicating a need for improving calibration and standardization. Analytical performance varied over the physiological range of glucose values so that separate accuracy and precision goals should be defined for hypoglycemic, normoglycemic, and hyperglycemic ranges. This study describes the current state of performance of blood glucose monitoring devices and points out those factors that should be assessed during evaluation of new devices.     

床旁监测血糖仪葡萄糖氧化酶法及脱氢酶法准确度评估

以生化分析仪检测为参照,比较葡萄糖氧化酶法及脱氢酶法血糖仪的准确度.检测新鲜肝素锂化静脉血临床样本.根据ISO15197,血糖仪的两种方法检测结果偏倚100%在±0.56 mmol/L内(＜4.2mmol/L),≥99.7%在±20%内(≥4.2 mmol/L);根据EF9-A2,两种方法的预期误差＜10%,略＞5%;低、高血糖症界值处(＜3.89 mmol/L或＞6.11mmol/L),两种方法的κ＞0.6.两种方法间的κ＜0.6.血糖仪葡萄糖氧化酶法、脱氢酶法准确度符合ISO15197要求,与生化分析仪检测方法的差异不影响临床应用,其结果用于低、高血糖症判读一致性好.

Abstract：

Blood samples were detected by 24 blood-glucose meters using glucose oxidase and another 18 glucose meters using glucose dehydrogenase. The plasma glucose was detected by the auto-chemistry analyzer as control. According to ISO1 5197 and EF9-A2, the bias of results from both glucose meters 100% fall in the range of ±0. 56 mmol/L( ＜4. 2 mmol/L) and ≥99. 7% in the range of ±20% ( ≥4. 2 mmol/L), predicted bias were all less than the true bias(Bc). As κ＞0. 6, the results from both glucose meters were in accordance with the results from autochemistry analyzer in judging hyperglycemia ( ＞6. 11 mmol/L) and hypoglycemia ( ＜ 3.89 mmol/L). Between the results from the two blood-glucose meters, κ＜0. 6. The accuracy of both glucose-meters are accepted for the purpose of clinical diagnosis and treatment.     

The ExacTech blood glucose testing system

The ExacTech system, a new device for home measurement of blood glucose was tested in the laboratory, in the out-patient clinic, and by diabetic patients. The system is based on an electrochemical principle, and consists of specially impregnated strips and a small, pencil-shaped meter. (1) Six meters were tested in the laboratory at blood glucose concentrations of 4, 10 and 20 mmol/l. Low coefficients of variation were found at 10 and 20 mmol/l, but those at 4 mmol/l were rather high (approximately 10%). Analysis of variances showed no difference in the between and the within variation of the meters. (2) The blood glucose concentrations of 50 consecutive out-patients were determined by the ExacTech system and a standard laboratory method. Correlation analysis showed an r value of 0.95 (P less than 0.001). (3) The results obtained by 13 patients repeating the correlation experiment were in agreement with the second part of the study. The ExacTech system is very simple to operate by the patients, and can be recommended for home monitoring of blood glucose.     

FreeStyle Mini? Blood Glucose Results Are Accurate and Suitable for Use in Glycemic Clamp Protocols

Objective

We assessed the accuracy of the FreeStyle Mini™ (FSM) meter for use in glycemic clamp and meal protocols in comparison with the HemoCue Glucose 201 DM Analyzer (HemoCue) and the YSI 2300 STAT Glucose Oxidase Analyzer (YSI).

Methods

Seven volunteers with type 2 diabetes mellitus, 35–69 years old, underwent a frequently sampled meal test and a graded hyperglycemic test, on two separate days, with one of the volunteers undergoing each test twice. Samples for glucose measurements were obtained from arterialized venous blood. A total of 420 samples (with glucose levels ranging from 63 to 388 mg/dl) were available for comparison. On average, 10 measurements were available for every 5 mg/dl increment in glucose level in the range of 130–310 mg/dl. Blood glucose measurements were done on each sample with the FSM, HemoCue, and YSI.

Results

FreeStyle Mini blood glucose values correlated closely with the YSI readings. Of the FSM measurements, 99.0% were within the Clarke error grid zone A; 51.3%, 84.7%, and 96.2% of the FSM readings were within 5%, 10% and 15% of the YSI values, respectively. The FSM was significantly more accurate than the HemoCue (84.7% vs 76.6% of results within 10% of the YSI results; p = .0038). The mean average relative difference of the FSM (5.8%) was also significantly lower than that of the HemoCue (6.8%; p = .0013)

Conclusions

The FSM provides accurate results and constitutes a suitable alternative for bedside blood glucose measurements in experimental procedures, helping to reduce sample size, turnaround time, and cost.     

Feasibility of continuous long-term glucose monitoring from a subcutaneous glucose sensor in humans

The feasibility of continuous long-term glucose monitoring in humans has not yet been demonstrated. Enzyme-based electrochemical glucose sensors with telemetric output were subcutaneously implanted and evaluated in five human subjects with type I diabetes. Subject-worn radio-receiver data-loggers stored sensor outputs. Every 1-4 weeks the subject's glucose levels were manipulated through the full clinical range of interest using standard protocols. Reference blood glucose samples were obtained every 5-10 min and analyzed in our hospital clinical laboratory and/or on glucose meters. The sensor data were evaluated versus the reference data by linear least squares regression and by the Clarke Error Grid method. After surgical explantation and device inspection, the tissue-sensor interface was evaluated histologically. The remaining sensor-membranes were also recalibrated for comparison with preimplant performance. Four of the five glucose sensors tracked glucose in vivo. One sensor responded to manipulated glucose changes for 6.2 months with clinically useful performance (>/=90% of sensor glucose values within the A and B regions of the Clarke Error Grid). For this sensor, recalibration was required every 1-4 weeks. The other three transiently responding sensors had electronic problems associated with packaging failure. The remaining sensor never tracked glucose because of failure to form any sustained connection to adjacent subcutaneous tissue. Thus, stable, clinically useful sensor performance was demonstrated in one of five subjects with diabetes for a sustained interval of greater than 6 months. While this glucose sensor implant technology shows promise in humans, it needs to be made more reliable and robust with respect to device packaging and sensor-tissue connection.     

Performance of a new blood glucose monitoring system in the hands of intended users

Abstract Background: This study assessed the performance of a blood glucose monitoring system (BGMS) in development that uses a new generation of blood glucose test strips with capillary and venous blood in the hands of its intended users, people with diabetes and healthcare professionals (HCPs). Subjects and Methods: In total, 93 subjects ≥18 years old (median age, 33 years) with type 1 (78%) or type 2 (22%) diabetes participated. Untrained subjects performed self-test fingersticks using a Microlet(?)2 lancing device (Bayer HealthCare LLC, Diabetes Care, Tarrytown, NY) followed by testing of their own capillary blood on the BGMS. HCPs performed fingersticks (using a Tenderlett(?) lancing device [International Technidyne Corp., Edison, NJ]) and venipunctures on subjects and tested both capillary and venous samples from subjects on the BGMS. All BGMS results were compared with Yellow Springs Instruments (YSI) (YSI Life Sciences, Inc., Yellow Springs, OH) laboratory results. Analytical accuracy was assessed according to International Organization for Standardization (ISO) 15197:2003 guidelines (i.e., within ±15?mg/dL or ±20% of the YSI results for samples with glucose concentrations <75?mg/dL and ≥75?mg/dL, respectively) and more stringent criteria (i.e., within ±15?mg/dL or ±15% of the YSI results for samples with glucose concentrations <100?mg/dL and ≥100?mg/dL, respectively). Results: Overall, 98.9% (180/182) of subject Microlet2 capillary fingerstick results, 99.5% (182/183) of HCP Tenderlett capillary fingerstick results, and 100% (186/186) of venous results met current ISO criteria and more stringent criteria. The average hematocrit was 44%, with values ranging from 32% to 52%. Conclusions: Test results from both capillary fingerstick and venous samples with a new BGMS in development met current accuracy guidelines as well as proposed tighter criteria.