Jane F. Wallace

Accuracy Evaluation of Five Blood Glucose Monitoring Systems: The North American Comparator Trial

Background: This study evaluated differences in accuracy between the CONTOUR® NEXT EZ (EZ) blood glucose monitoring system (BGMS) and four other BGMSs [ACCU-CHEK® Aviva (ACAP), FreeStyle Freedom Lite® (FFL), ONE TOUCH® Ultra®2 (OTU2), and TRUEtrack® (TT)]. Methods: Up to three capillary blood samples (N = 393) were collected from 146 subjects with and without diabetes. One sample per subject was tested with fresh (natural) blood; the other samples were glycolyzed to lower blood glucose to <70 mg/dl. Meter results were compared with results from plasma from the same sample tested on a Yellow Springs Instruments (YSI) 2300 STAT Plus™ glucose analyzer. Blood glucose monitoring system accuracy was compared using mean absolute relative difference (MARD; from laboratory reference method results) and other analyses. Separate analyses on fresh (natural) samples only were conducted to determine potential effects of glycolysis on MARD values of systems utilizing glucose-oxidase-based test strip chemistry. Results: Across the tested glucose range, the EZ had the lowest MARD of 4.7%; the ACAP, FFL, OTU2, and TT had MARD values of 6.3%, 18.3%, 23.4%, and 26.2%, respectively. For samples with glucose concentrations <70 mg/dl, the EZ had the lowest MARD (0.65%), compared with the ACAP (2.5%), FFL (18.3%), OTU2 (22.4%), and TT (33.2%) systems. Conclusions: The EZ had the lowest MARD across the tested glucose ranges when compared with four other BGMSs when all samples were analyzed as well as when natural samples only were analyzed.

Performance of the CONTOUR® TS Blood Glucose Monitoring System

Background: Self-monitoring of blood glucose (SMBG) remains an important component of diabetes management, engendering a need for affordable blood glucose (BG) meters that are accurate, precise, and convenient. The CONTOUR® TS is a BG meter that endeavors to meet this need. It uses glucose dehydrogenase/flavin dinucleotide chemistry, automatic test strip calibration, and autocompensation for hematocrit along with the ease of use that has come to be expected of a modern meter. The objective of this clinical trial was to determine whether the CONTOUR TS system met these criteria. Methods: The system was evaluated at a single clinical site with 106 subjects with type 1 or type 2 diabetes. Blood glucose values ranged from 60 to 333 mg/dl over all subjects. Both lay users and health care professionals (HCPs) tested the meters, with test strips from three different lots. Results were compared to a reference analyzer of verified precision and accuracy. Forty-nine of the subjects also participated in a home study of the meter. Lay users learned to use the system without assistance and were surveyed on its use at the end of the study. Results: When used with capillary blood, both subjects and HCPs obtained results that exceeded the International Organization for Standardization 15197:2003 criteria, (i.e., ≥95% of values fell within 20% or 15 mg/dl of the laboratory value for BG levels greater than or less than 75 mg/dl, respectively). Specifically, lay users achieved 97.9% and HCPs 98.6%. When used with venous blood, 99.8% of measurements were within the criteria. All measurements for both capillary and venous blood fell into zones A or B of the Parkes error grid, deemed clinically accurate. Hematocrit was found to have no influence on BG measurements. A large majority of the subjects found the system easy to learn and to use. Conclusions: The CONTOUR TS BG meter system gave accurate and reproducible results with both capillary and venous blood; subjects learned to use the meter system by following the user guide and quick reference guide.

Performance Evaluation of Three Blood Glucose Monitoring Systems Using ISO 15197: 2013 Accuracy Criteria, Consensus and Surveillance Error Grid Analyses, and Insulin Dosing Error Modeling in a Hospital Setting.

Background: Blood glucose monitoring is an essential component of diabetes management. Inaccurate blood glucose measurements can severely impact patients’ health. This study evaluated the performance of 3 blood glucose monitoring systems (BGMS), Contour® Next USB, FreeStyle InsuLinx®, and OneTouch® Verio™ IQ, under routine hospital conditions. Methods: Venous blood samples (N = 236) obtained for routine laboratory procedures were collected at a Spanish hospital, and blood glucose (BG) concentrations were measured with each BGMS and with the available reference (hexokinase) method. Accuracy of the 3 BGMS was compared according to ISO 15197:2013 accuracy limit criteria, by mean absolute relative difference (MARD), consensus error grid (CEG) and surveillance error grid (SEG) analyses, and an insulin dosing error model. Results: All BGMS met the accuracy limit criteria defined by ISO 15197:2013. While all measurements of the 3 BGMS were within low-risk zones in both error grid analyses, the Contour Next USB showed significantly smaller MARDs between reference values compared to the other 2 BGMS. Insulin dosing errors were lowest for the Contour Next USB than compared to the other systems. Conclusions: All BGMS fulfilled ISO 15197:2013 accuracy limit criteria and CEG criterion. However, taking together all analyses, differences in performance of potential clinical relevance may be observed. Results showed that Contour Next USB had lowest MARD values across the tested glucose range, as compared with the 2 other BGMS. CEG and SEG analyses as well as calculation of the hypothetical bolus insulin dosing error suggest a high accuracy of the Contour Next USB.

Accuracy and user performance evaluation of the Contour® Next Link 2.4 blood glucose monitoring system

BACKGROUND The Contour(®) Next Link 2.4 blood glucose monitoring system (BGMS), which communicates wirelessly exclusively with a Medtronic insulin pump, was assessed in 2 separate studies. METHODS In the laboratory study (N=100), subject capillary fingertip samples were tested in duplicate using 3 test strip lots; accuracy was assessed based on ISO 15197:2013 section 6.3 accuracy criteria (95% within ±15mg/dl or ±15% of reference for glucose <100 and ≥100mg/dl, respectively). In the clinical trial (N=219), untrained subjects with diabetes tested capillary fingertip and palm blood samples and completed an ease-of-use questionnaire. BGMS and YSI glucose analyzer results were compared based on ISO 15197:2013 section 8 accuracy criteria. RESULTS In the laboratory study, 100% of results met ISO 15197:2013 section 6.3 accuracy criteria. In the clinical trial, 98.6% of capillary fingertip and 97.2% of palm results from subjects met ISO 15197:2013 section 8 accuracy criteria. By Parkes-Consensus Error Grid analysis, 100% of subject capillary fingertip results were within Zone A. Based on questionnaire results, the majority of subjects found the BGMS easy to use. CONCLUSIONS The BGMS exceeds ISO 15197:2013 section 6.3 and section 8 accuracy criteria in the laboratory and in the hands of untrained users with diabetes.

Performance of a New Blood Glucose Monitoring System in the Hands of Intended Users

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.

Accuracy and User Performance Evaluation of a New, Wireless-enabled Blood Glucose Monitoring System That Links to a Smart Mobile Device.

Background: The new Contour®Plus ONE blood glucose monitoring system (BGMS) features an easy-to-use, wireless-enabled blood glucose meter that links to a smart mobile device via Bluetooth® connectivity and can sync with the Contour™ Diabetes app on a smartphone or tablet. Methods: The accuracy of the new BGMS was assessed in 2 studies according to ISO 15197:2013 criteria. In Study 1 (laboratory study), fingertip capillary blood samples from 100 subjects were tested in duplicate using 3 test strip lots. In Study 2 (clinical study), 134 subjects with type 1 or type 2 diabetes enrolled at 2 clinical sites. BGMS results and YSI analyzer (YSI) reference results were compared for fingertip blood obtained by untrained subjects’ self-testing and for study staff–obtained fingertip, subject palm, and venous results. Results: In Study 1, 99.0% (594/600) of combined results for all 3 test strip lots fulfilled ISO 15197:2013 Section 6.3 accuracy criteria. In Study 2, 99.2% (133/134) of subject-obtained capillary fingertip results, 99.2% (133/134) of study staff–obtained fingertip results, 99.2% (125/126) of subject-obtained palm results, and 100% (132/132) of study staff–obtained venous results met ISO 15197:2013 Section 8 accuracy criteria. Moreover, 95.5% (128/134) of subject-obtained fingertip self-test results were within ±10 mg/dl (±0.6 mmol/L) or ±10% of the YSI reference result. Questionnaire results showed that most subjects found the BGMS easy to use. Conclusions: The BGMS exceeded ISO 15197:2013 accuracy criteria both in the laboratory and in a clinical setting when used by untrained subjects with diabetes.

A Multicenter Performance Evaluation of a Blood Glucose Monitoring System in 21 Leading Hospitals in Spain

Background: Self-monitoring of blood glucose is crucial for the effective self-management of diabetes. The present study evaluated the accuracy of the Contour® XT blood glucose monitoring system (BGMS) compared to the reference method in a large multicenter study under routine lab conditions at each hospital site. Methods: This study was conducted at 21 leading hospitals in Spain using leftover whole blood samples (n = 2100). Samples were tested with the BGMS using 1 commercial strip lot and the local laboratory hexokinase method. BGMS accuracy was assessed and results were compared to ISO 15197:2013 accuracy limit criteria and by using mean absolute relative difference analysis (MARD), consensus (Parkes) error grid (CEG), and surveillance error grid analyses (SEG). Results: Pooled analysis of 2100 measurements from all sites showed that 99.43% of the BGMS results were within the ranges accepted by the accuracy limit criteria. The overall MARD was 3.85%. MARD was 4.47% for glucose concentrations < 70 mg/dL and 3.81% for concentrations of 70-300 mg/dL. In CEG, most results (99.8%) were within zone A (“no effect on clinical action”); the remaining ones (0.2%) were in zone B (“little to no effect on clinical action”). The SEG analysis showed that most of the results (98.4%) were in the “no risk” zone, with the remaining results in the “slight, lower” risk zone. Conclusions: This is the largest multicenter study of Contour XT BGMS to date, and shows that this BGMS meets the ISO 15197:2013 accuracy limit criteria under local routine conditions in 21 leading Spanish hospitals.

Fundamental Importance of Reference Glucose Analyzer Accuracy for Evaluating the Performance of Blood Glucose Monitoring Systems (BGMSs).

Background: As blood glucose monitoring system (BGMS) accuracy is based on comparison of BGMS and laboratory reference glucose analyzer results, reference instrument accuracy is important to discriminate small differences between BGMS and reference glucose analyzer results. Here, we demonstrate the important role of reference glucose analyzer accuracy in BGMS accuracy evaluations. Methods: Two clinical studies assessed the performance of a new BGMS, using different reference instrument procedures. BGMS and YSI analyzer results were compared for fingertip blood that was obtained by untrained subjects’ self-testing and study staff testing, respectively. YSI analyzer accuracy was monitored using traceable serum controls. Results: In study 1 (N = 136), 94.1% of BGMS results were within International Organization for Standardization (ISO) 15197:2013 accuracy criteria; YSI analyzer serum control results showed a negative bias (−0.64% to −2.48%) at the first site and a positive bias (3.36% to 6.91%) at the other site. In study 2 (N = 329), 97.8% of BGMS results were within accuracy criteria; serum controls showed minimal bias (<0.92%) at both sites. Conclusions: These findings suggest that the ability to demonstrate that a BGMS meets accuracy guidelines is influenced by reference instrument accuracy.

Comparative Accuracy of 3 Blood Glucose Monitoring Systems that Communicate with an Insulin Pump.

OBJECTIVE This study compared the accuracy of the Contour® Next Link blood glucose monitoring system (BGMS) with 2 other BGMSs (OneTouch® UltraLink® and Nova Max Link™), all 3 of which can communicate wirelessly with an insulin pump. METHODS Study staff tested fingerstick samples from 112 subjects aged ≥18 years with each BGMS. All BGMS results were compared to YSI 2300 STAT Plus™ Glucose Analyzer results from the same sample source. To safely obtain a wide range of glucose values, 3 blood samples were obtained from each subject (1 sample was tested fresh from the fingertip [unmodified], and the other 2 samples were modified to raise or lower the glucose concentration). The primary endpoint evaluated was difference in accuracy among the BGMSs across the entire tested glucose range (34 to 561 mg/dL). Additional comparisons were made of accuracy in the low (≤80 mg/dL) and high (>180 mg/dL) glucose ranges. BGMS accuracy was assessed by mean absolute relative difference (MARD). RESULTS The Contour® Next Link BGMS had a statistically significantly lower MARD from the reference value than the other BGMSs across the entire tested glucose range, calculated using all samples as well as only unmodified (i.e., natural) samples. In the low and high glucose ranges, the Contour® Next Link also had a statistically significantly lower MARD from the reference value than the other BGMSs. CONCLUSION As assessed by MARD, the Contour® Next Link BGMS was significantly more accurate than the other BGMSs evaluated, all of which can communicate wirelessly with an insulin pump.

Performance of the DIDGET Blood Glucose Monitoring System in Children, Teens, and Young Adults

Background: This study evaluated the performance of the DIDGET® blood glucose monitoring system (BGMS) in the hands of its intended users: Children, teens, and young adults with diabetes. Methods: Finger stick capillary blood samples were tested in duplicate by subjects (with parent/guardian assistance, if needed) and health care professionals using the DIDGET BGMS, and results were compared with those obtained using a Yellow Springs Instruments (YSI) glucose analyzer. Modified venous blood samples (i.e., glycolyzed or spiked with glucose) were used to analyze meter performance under extreme glucose concentrations. Accuracy was assessed using International Organization for Standardization (ISO) 15197:2003 guidelines (i.e., 95% of meter results within ±15 mg/dl or ±20% of reference values). Results: A total of 123 subjects aged 4 to 24 years with type 1 or type 2 diabetes were enrolled. The DIDGET meter achieved accuracy according to ISO 15197:2003 criteria: >97% of meter results were within ±15 mg/dl or ±20% of reference values. Regression analyses showed a high degree of correlation between meter and YSI results: Coefficient of determination (R 2) = 98.2% for all samples combined and 97.2% for capillary samples only. Clinical accuracy for combined samples was demonstrated by Parkes consensus error grid analyses; 100% of meter results were in zone A (98.5%) or zone B (1.5%). There was no difference in performance or accuracy across age subsets. Hematocrit values did not affect meter blood glucose results. Conclusion: The DIDGET BGMS provided accurate test results across all age ranges in children, teens, and young adults with diabetes.