Measurement accuracy of two professional-use systems for point-of-care testing of blood glucose.

Background The professional-use systems HemoCue® Glucose 201+ (HC201+) and HemoCue® Glucose 201 RT (HC201RT) are widely used for point-of-care testing (POCT) of blood glucose (BG). HC201RT utilizes unit-use microcuvettes which can be stored at room temperature, whereas HC201+ microcuvettes have to be stored at <8 °C. In this study, system accuracy of HC201+ and HC201RT was evaluated using capillary and venous blood samples. Methods For each system, two reagent system lots were evaluated within a period of 2 years based on testing procedures of ISO 15197:2013, a standard applicable for self-monitoring of blood glucose (SMBG) systems. For each reagent system lot, the investigation was performed by using 100 capillary and 95 to 99 venous blood samples. Comparison measurements were performed with a hexokinase laboratory method. Accuracy criteria of ISO 15197:2013 and POCT12-A3 were applied. In addition, bias was analyzed according to Bland and Altman, and error grid analysis was performed. Results When measuring capillary samples, both systems fulfilled accuracy requirements of ISO 15197:2013 and POCT12-A3 with the investigated reagent system lots. When measuring venous samples, only HC201+ fulfilled these requirements. Bias between HC201+ and reference measurements was more consistent over venous and capillary samples and microcuvette lots than for HC201RT. Error grid analysis showed that clinical actions might have been different depending on which system was used. Conclusions In this study, HC201+ showed a high level of accuracy irrespective of the sample type (capillary or venous). In contrast, HC201RT measurement results were markedly affected by the type of sample.

System accuracy evaluation of systems for point-of-care testing of blood glucose: a comparison of a patient-use system with six professional-use systems.

BACKGROUND: Point-of-care testing (POCT) of blood glucose (BG) is performed by medical personnel in clinical settings as well as by patients themselves for self-monitoring of blood glucose (SMBG) at home. We investigated if a system mainly intended for SMBG by people with diabetes, but also suitable for BG measurements by medical personnel, can achieve measurement accuracy on capillary blood samples comparable with professional-use POCT systems. METHODS: System accuracy was evaluated under standardised conditions, following the ISO standard 15197:2003. For each system (one SMBG system with three test strip lots and six professional-use systems), measurement results from capillary blood samples of 100 subjects were compared with a standardised laboratory glucose oxidase method (YSI 2300 glucose analyser). RESULTS: The seven evaluated systems showed 99.5% or 100% of the measurement results within the required system accuracy limits of ISO 15197:2003 (±0.83 mmol/L at BG concentrations <4.2 mmol/L and ±20% at BG concentrations ≥4.2 mmol/L). Applying the more stringent requirements of the revision ISO 15197:2013, the systems showed between 99% and 100% of the measurement results within the accuracy limits (±0.83 mmol/L at BG concentrations <5.55 mmol/L and ±15% at BG concentrations ≥5.55 mmol/L) and between 82% and 98% when even more restrictive limits were applied (±0.56 mmol/L and ±10%, respectively). CONCLUSIONS: Data from this study, which focused on system accuracy, suggest that SMBG systems can achieve system accuracy that is comparable with professional-use systems when measurements are performed on capillary blood samples by trained personnel in a standardised and controlled setting.

Plasma Glucose Concentrations in Different Sampling Tubes Measured on Different Glucose Analysers.

INTRODUCTION: The German Diabetes Association recommends using sampling tubes with citrate and fluoride additives to diagnose diabetes by oral glucose tolerance test to inhibit glycolysis. The effect of different tubes on measurement results was assessed. MATERIALS AND METHODS: In a first study, an oral glucose tolerance test was performed on 41 participants without anamnestically known diabetes. Venous blood was sampled in two different tubes with citrate/fluoride additives from different manufacturers and one with only lithium-heparin additive. A second study with 42 participants was performed to verify the initial results with an adapted design, in which a third tube with citrate buffer was used, and glucose measurements were performed on two additional devices of another analyser model. Samples were centrifuged either immediately (<5 min incubation time) or after 20 min or 4 h. All glucose measurements were performed in plasma. Glucose concentrations in lithium-heparin tubes with<5 min incubation time served as baseline concentrations. RESULTS: In the first study, glucose concentrations in one of the citrate/fluoride tubes were similar to the baseline. In the other citrate/fluoride tube, markedly lower concentrations (approximately - 5 mg/dL (- 0.28 mmol/L)) were measured. This was reproduced in the verification study for the same analyser, but not with the other analyser model. Lithium-heparin tubes centrifuged after 20 and 240 min showed systematically lower glucose concentrations. CONCLUSIONS: The results confirm that glycolysis can be effectively inhibited in citrate/fluoride-containing sampling tubes. However, glucose measurement results of one analyser showed a relevant negative bias in tubes containing liquid citrate buffer.

Evaluation of System Accuracy, Precision, Hematocrit Influence, and User Performance of Two Blood Glucose Monitoring Systems Based on ISO 15197:2013/EN ISO 15197:2015.

INTRODUCTION: Sufficiently high analytical quality of blood glucose monitoring systems (BGMS) is a prerequisite for efficient diabetes therapy. In this study we assessed system accuracy, measurement repeatability, intermediate measurement precision, user performance, and the influence of hematocrit on two CE-marked blood glucose monitoring systems. For one BGMS, measurement accuracy using venous samples was additionally investigated. METHODS: Study procedures were based on the International Organization of Standardization (ISO) 15197:2013/EN ISO 15197:2015 ("ISO 15197"). User performance included data from 100 subjects who used one test strip lot, whereas for all other analyses three different reagent system lots were used. For system accuracy assessment, 100 capillary samples were measured in duplicate with each of three reagent system lots per system, resulting in 600 results per system. RESULTS: CareSens S Fit and CareSens H Beat both fulfilled the ISO 15197 accuracy criteria with 97.5-100% of each test strip lot's results falling within ± 15 mg/dL or ± 15% of the results of the comparison method and 100% of results in consensus error grid (CEG) zone A for all three lots. User performance evaluation revealed sufficient accuracy in the hands of lay users although some handling errors were documented by study staff. Assessment of measurement repeatability and intermediate measurement precision is given by standard deviation (SD) (glucose levels < 100 mg/dL) and by coefficient of variation (CV) (glucose concentrations ≥ 100 mg/dL). SD was ≤ 4.1 mg/dL and CV ≤ 4.2% for measurement repeatability and SD was ≤ 2.2 mg/dL and CV ≤ 2.6% for intermediate measurement precision. In case of hematocrit influence, both BGMS complied with all three tested lots with the defined criteria. CONCLUSION: Both BGMS analyzed in this study fulfilled the required accuracy criteria of ISO 15197. They showed high precision, good performance in the hands of lay users, and the influence of hematocrit was acceptable in the labeled range.

Effect of Arterialization on Venous Blood Glucose Concentrations and Implications for Observed Continuous Glucose Monitoring Accuracy.

Background: Heating of the arm and/or hand ("arterialization") is sometimes used in continuous glucose monitoring (CGM) performance studies with the reported aim of reducing differences between venous and capillary glucose concentrations. In this study, the effect of heating on venous glucose concentrations and CGM accuracy was investigated. Methods: A heating pad set to 50°C (122°F) was used with 20 participants to heat either the dominant or nondominant arm and hand. Venous and capillary samples were obtained every 15 min on both arms throughout each of three 6-h glucose challenges. CGM sensors were worn on each upper arm for each of the three visits. Results: Heating of the arm led to a median increase in venous glucose concentrations of +1.4%. No similar effect on capillary concentrations was observed. As a result, the median capillary to venous difference decreased from +5.9% in the nonheated arm to +4.2% in the heated arm. CGM accuracy observed in this study was affected by the selection of heated venous, nonheated venous, or capillary glucose concentrations as comparator data. The heating effect was more pronounced with rapidly decreasing glucose concentrations. Temperatures on the skin did not exceed 40°C (104°F). No adverse events or protocol deviations were associated with the use of the heating pad. Conclusions: Heating of the arm led to a small increase in venous glucose concentrations, but venous concentrations did not reach the level of capillary glucose concentrations. CGM accuracy observed in this study varied depending on the selected comparator data. This study was registered at the German Clinical Trials Register (DRKS00031197).

Investigation of the Effect of 70 Potential Interferents on Measurement Results of Two Blood Glucose Monitoring Systems.

BACKGROUND: Reliable blood glucose (BG) measurements are important for people with diabetes to manage their therapy as well as in point-of-care testing (POCT) performed by health care professionals to monitor BG of patients or even to diagnose diabetes. Among other factors, endogenous and exogenous substances present in blood samples can impact the measurement results. To ensure and prove that blood glucose monitoring systems (BGMSs) are robust in terms of potential interferents, manufacturers have to perform extensive evaluations. METHOD: An interference screening test was performed for three reagent system lots of a POCT system and of a BGMS for self-monitoring of BG. A paired-difference approach based on ISO 15197:2013 and CLSI guideline EP07 was used with venous whole blood samples at two different glucose concentrations. Seventy potential interferents expected to be common in people with diabetes were evaluated. RESULTS: The interference effects were determined as normalized biases between test samples and corresponding control samples. For 69 of the 70 investigated potential interferents, both systems met the predefined acceptance criteria, with the normalized biases falling within ±10 mg/dL or ±10% at glucose concentrations ≤100 mg/dL or >100 mg/dL, respectively, for each of the three evaluated reagent system lots. CONCLUSIONS: The BGMS investigated in this study were found to be robust with respect to the 70 evaluated potential interferents. Interference effects were observed only for N-Acetyl-L-cysteine. Extensive evaluations of potential interfering factors can make an important contribution to ensure reliability of BGMS.

Monitoring of the Analytical Performance of Four Different Blood Glucose Monitoring Systems: A Post-market Performance Follow-Up Study.

INTRODUCTION: A sizeable minority of commercially available blood glucose monitoring (BGM) systems fail to satisfy regulatory accuracy requirements, such as ISO 15197:2013, after approval. This study assessed whether the BGMs tested could consistently meet these ISO requirements by investigating their accuracy in a non-standardized setting. METHODS: In this 18-month post-market performance study, using the ISO criteria, healthcare professionals tested the accuracy of four CE-marked BGM systems (Roche Diabetes Care, Mannheim, Germany) on European adults with diabetes mellitus. ISO criteria included 95% of blood glucose (BG) values being within ± 15 mg/dl of a reference measurement for BG < 100 mg/dl or ± 15% for BG ≥ 100 mg/dl and, in the Parkes Consensus Error grid for type 1 diabetes comparing capillary BGM measurements versus reference method, 99% of BG values falling within zone A (no effect on clinical action or outcome) and zone B (altered clinical action with little or no effect on clinical outcome). RESULTS: BGM readings were obtained from 1650 participants, and the number of readings per BGM system was between 1712 and 2376. The percentage of BGM readings that fell within ISO 15197:2013 limits ranged from 99.4 to 99.9%. For all meter types, 100% of data points fell within zone A or zone B, and most data points for each meter (≥ 99.9%) were in zone A. CONCLUSION: All four CE-marked BGM models showed results within the accuracy limits defined by ISO 15197 in a non-standardized setting and thus consistently met regulatory accuracy requirements.

Accuracy Evaluation of a Novel Reusable Patch Pump Prototype.

A prototype of an insulin patch pump that operates with a double pump mechanism was tested. Accuracy of bolus delivery of 0.2 U and 1.0 U, and a basal rate of 1.0 U/h were evaluated with a microgravimetric method. In addition, occlusion detection time at basal rates of 0.1 U/h and 1.0 U/h was assessed. Mean deviation from target was lower than 2% for both bolus sizes. Regarding basal rate accuracy, mean deviation over 72 hours was lower than 1%. Occlusion detection occurred in less than 30 minutes with both basal rates. Our study results suggest that the tested pump prototype provides delivery accuracy and occlusion detection that is similar or even better compared to all commercially available pumps tested with a similar experimental approach.

Stability of Glucose Concentrations in Frozen Plasma.

BACKGROUND: Conflicting information is available regarding the stability of glucose concentrations in frozen plasma samples. Clinical trials could benefit from such long-term storage because it would allow usage of a central laboratory with higher-quality laboratory analyzers in contrast to mobile analyzers in a decentralized setting. METHODS: In this study, venous blood samples were collected in lithium-heparin gel tubes. Plasma was separated immediately after blood was drawn, and from each of the 21 plasma samples, 6 aliquots were prepared for measurement at 6 time points: immediately and after 2, 4, 6, 8, and 12 weeks. Between sampling and measurement, aliquots were stored at less than -20°C. Transport on dry ice was simulated by placing aliquots in a -80°C freezer for 5 days between weeks 8 and 12. Measurements were performed on a hexokinase-based laboratory analyzer.Average relative differences and corresponding 99% confidence intervals (CIs) were calculated between the stored aliquots' and the immediately measured aliquots' glucose concentrations. Glucose concentrations were deemed stable as long as average relative differences were ≤±2.5%. RESULTS: Over the whole 12-weeks duration, the largest average relative difference was -1.82% (99% CI: -2.25% to -1.39%). Shorter storage durations tended to lead to less bias. CONCLUSION: In this study, the stability of glucose concentrations in frozen plasma samples obtained with lithium-heparin gel tubes could be shown for up to 12 weeks. Future studies should be performed to assess whether this is independent of the glucose analyzer and the type of sampling tube used.

Evaluation of Trueness and Precision of a Bench-Top Laboratory Glucose Analyzer Using Reference Materials.

SUPER GL compact is a bench-top analyzer for glucose, lactate, and hemoglobin concentrations. Glucose measurements in the biosensor are based on an enzymatic-amperometric reaction of glucose with glucose oxidase.In this study, trueness and precision were assessed with Standard Reference Material 965b (National Institute of Standards and Technology, Gaithersburg, MD) for 2 SUPER GL compact (S1 and S2) and 1 YSI 2300 STAT Plus (Y) device, using a protocol based on CLSI EP05-A3.Precision was similar among S1, S2, and Y. S1 and S2 exhibited negative bias at low concentrations and positive bias at high concentrations, whereas Y showed negative bias that increased with higher concentrations. Overall, SUPER GL compact's performance was comparable to that of YSI 2300 STAT Plus.

Description of a Novel Patch Pump for Insulin Delivery and Comparative Accuracy Evaluation.

A new insulin patch pump for continuous subcutaneous insulin infusion was developed. The pump is composed of reusable and disposable parts and operates with a stepping motor. This pump was compared to a patch pump and a durable pump regarding basal rate and bolus accuracy. Using a microgravimetric method, boluses of 0.2 U, 1 U and 7 U, and a basal rate of 1 U/h were tested. For all pumps, bolus accuracy was higher when larger volumes were delivered. While median deviations were similar for all pumps, there were differences in the precision of individual boluses and when regarding basal rate delivery divided into 1-h windows.

User Performance Evaluation and System Accuracy Assessment of Four Blood Glucose Monitoring Systems With Color Coding of Measurement Results.

BACKGROUND: Blood glucose monitoring systems (BGMSs) are a cornerstone in diabetes management. They have to provide sufficiently accurate results in the hands of lay users, particularly in insulin-treated patients. The aim of this study was user performance evaluation and system accuracy assessment of four BGMSs with color coding of results. METHODS: Study procedures were based on ISO 15197:2013. User performance evaluation included data from 100 participants, each of whom used every system with one reagent lot. Study personnel observed user techniques. For the system accuracy assessment, 100 capillary samples were obtained for measurement in duplicate with each of three reagent system lots per system, resulting in 600 results per system. RESULTS: All assessed BGMSs exhibited a sufficient level of accuracy, with small differences between them. In the user performance evaluation, study personnel observed the smallest total number of user errors with Contour Next (Ascensia), followed by Accu-Chek Instant (Roche), Medisafe Fit Smile (Terumo), and OneTouch Ultra Plus Reflect (LifeScan). Approximately 90% of participants stated that a consistent color scheme, eg, for low blood glucose (BG) values, should be used across all BGMSs. There was no clear preference among the four tested BGMSs regarding the specific way of displaying color coding. CONCLUSIONS: The four BGMSs assessed in this study showed only small differences in an overall sufficient level of accuracy. User handling errors, as observed by study personnel, differed between the systems.

Mean Absolute Relative Difference of Blood Glucose Monitoring Systems and Relationship to ISO 15197.

BACKGROUND: The analytical quality of a blood glucose monitoring system (BGMS) is often assessed according to the requirements described in the international standard ISO 15197. However, the mean absolute relative difference (MARD) is sometimes used as well. This analysis aims at providing empirical data from BGMS evaluation studies conducted according to ISO 15197 and at providing an estimation of how MARD and percentage of measurement results within ISO accuracy limits are related. METHODS: Results of 77 system accuracy evaluations conducted according to ISO 15197 were used to calculate MARD between BGMS and a laboratory comparison method's results (glucose oxidase or hexokinase method). Additionally, bias and 95%-limits of agreement (LoA) using the Bland and Altman method were calculated. RESULTS: MARD results ranged from 2.3% to 20.5%. The lowest MARD of a test strip lot that showed <95% of results within ISO limits was 6.1%. The distribution of MARD results shows that only 3.6% of test strip lots with a MARD equal to or below 7% showed <95% of results within ISO limits (2.2% of all test strip lots). Bias of test strip lots that showed ≥95% of results within the limits ranged from -10.3% to +7.4%. The half-width of the 95%-LoA of test strip lots that showed ≥95% of results within the limits ranged from 4.8% to 24.0%. CONCLUSION: There is a threshold MARD that may allow an estimate whether ISO 15197 requirements are fulfilled, but this statement cannot be made with certainty.

Impact of Two Different Reference Measurement Procedures on Apparent System Accuracy of 18 CE-Marked Current-Generation Blood Glucose Monitoring Systems.

BACKGROUND: Measurement accuracy has been assessed for many different blood glucose monitoring systems (BGMS) over the years by different study groups. However, the choice of the comparison measurement procedure may impact the apparent level of accuracy found in such studies. MATERIALS AND METHODS: Measurement accuracy of 18 different BGMS was assessed in a setting based on ISO 15197 using two different comparison methods in parallel: a glucose oxidase (GOD)-based and a hexokinase (HK)-based method. Accuracy limits of ISO 15197 were applied, and additional analyses were performed, including bias, linear regression, and mean absolute relative difference (MARD) to assess the impact of possible differences between comparison methods on the apparent level of accuracy. RESULTS: While ≈80% of BGMS met the accuracy criteria of ISO 15197 when compared with the respective manufacturers' reference measurement procedure, only two-thirds did so against both comparison methods. The mean relative bias ranged from -6.6% to +5.7% for the analysis against the GOD-based method and from -11.1% to +1.3% for the analysis against the HK-based method, whereas MARD results ranged from 3.7% to 9.8% and from 2.3% to 10.5%, respectively. Results of regression analysis showed slopes between 0.85 and 1.08 (GOD-based method) and between 0.81 and 1.01 (HK-based method). CONCLUSIONS: The results of this study indicate that there are systematic differences between the reference measurement procedures used for BGMS calibration as well as for system accuracy assessment. Because of the potential impact on therapy of patients with diabetes resulting from these differences, further steps toward harmonization of the measurement procedures' results are important.

Continuous Glucose Profiles in Healthy People With Fixed Meal Times and Under Everyday Life Conditions.

BACKGROUND: The increased use of continuous glucose monitoring (CGM) and automated insulin delivery systems raises the question about therapeutic targets for glucose profiles in people with diabetes. This study aimed to assess averaged pre- and postprandial glucose profiles in people without diabetes to provide guidance for normal glucose patterns in clinical practice. For that, number and timing of meal intake were predefined. MATERIAL AND METHODS: To assess glucose traces in 36 participants without diabetes (mean age = 23.7 ± 5.7 years), CGM was performed for up to 14 days, starting with a run-in phase (first 3 days, excluded from analysis) followed by 4 days with fixed meal times at 8:00 am, 1:00 pm, and 6:00 pm and the remaining 7 days spent under everyday life conditions. Data from two simultaneously worn CGM sensors were averaged and adjusted to capillary plasma-equivalent glucose values. Glucose data were evaluated through descriptive statistics. RESULTS: Median glucose concentration on days with fixed meal times and under everyday life conditions was 95.0 mg/dL (91.6-99.1 mg/dL, interquartile range) and 98.1 mg/dL (93.7-100.8 mg/dL), respectively. On days with fixed meal times, mean premeal glucose was 92.8 ± 9.4 mg/dL, and mean peak postmeal glucose was 143.3 ± 23.5 mg/dL. CONCLUSIONS: By defining the time of meal intake, a clear pattern of distinct postprandial glucose excursions in participants without diabetes could be demonstrated and analyzed. The presented glucose profiles might be helpful as an estimate for adequate clinical targets in people with diabetes.

System accuracy evaluation of 18 CE-marked current-generation blood glucose monitoring systems based on EN ISO 15197:2015.

OBJECTIVE: Accuracy of 18 current-generation blood glucose monitoring systems (BGMS) available in Europe was evaluated applying criteria adapted from EN ISO 15197:2015 with one reagent system lot. BGMS were selected based on market research data. RESEARCH DESIGN AND METHODS: The BGMS ABRA, Accu-Chek Guide, AURUM, CareSens Dual, CERA-CHEK 1CODE, ContourNext One, eBsensor, FreeStyle Freedom Lite, GL50 evo, GlucoCheck GOLD, GlucoMen areo 2K, GluNEO, MyStar DoseCoach, OneTouch Verio Flex, Pic GlucoTest, Rightest GM700S, TRUEyou, and WaveSense JAZZ Wireless were tested using capillary blood from 100 different subjects and assessing the percentage of results within ±15 mg/dL (0.83 mmol/L) or 15% of comparison method results for BG concentrations below or above 100 mg/dL (5.55 mmol/L), respectively. In addition, the minimal deviation from comparison method results within which ≥95% of results of the respective BGMS were found was calculated. RESULTS: In total, 14 BGMS had ≥95% of results within ±15 mg/dL (0.83 mmol/L) or ±15% and 3 BGMS had ≥95% of results within ±10 mg/dL (0.55 mmol/L) or ±10% of the results obtained with the comparison method. The smallest deviation from comparison method results within which ≥95% of results were found was ±7.7 mg/dL (0.43 mmol/L) or ±7.7%; the highest deviation was ±19.7 mg/dL (1.09 mmol/L) or ±19.7%. CONCLUSIONS: This accuracy evaluation shows that not all CE-labeled BGMS fulfill accuracy requirements of ISO 15197 reliably and that there is considerable variation even among BGMS fulfilling these criteria. This safety-related information should be taken into account by patients and healthcare professionals when making therapy decisions. TRIAL REGISTRATION NUMBER: NCT03737188.

Comment on "accuracy and precision of four main glucometers used in a sub-Saharan African country: a cross-sectional study" by Choukem et al.

In their article, Choukem et al. report of assessments of the analytical quality of blood glucose monitoring systems. Although there are some commendable aspects regarding the methodology, some major shortcomings could preclude the conclusions drawn by Choukem et al. Nevertheless, independent assessments of the performance of blood glucose monitoring systems are an important issue.

Evaluation of Analytical Performance of Three Blood Glucose Monitoring Systems: System Accuracy, Measurement Repeatability, and Intermediate Measurement Precision.

INTRODUCTION: Blood glucose monitoring systems (BGMS) should provide sufficient analytical quality to allow adequate therapy for diabetes patients. Besides system accuracy, measurement precision is an important aspect of a BGMS' analytical quality. METHODS: Based on ISO 15197:2013/EN ISO 15197:2015, system accuracy, measurement repeatability, and intermediate measurement precision were assessed. ISO 15197:2013 system accuracy criteria require that ⩾95% of individual BGMS' test strip lot results shall fall within ±15 mg/dl or ±15% of corresponding comparison method results (at glucose concentrations <100 mg/dl and ⩾100 mg/dl, respectively), and that ⩾99% of results fall within consensus error grid (CEG) zones A and B. Measurement repeatability was assessed using venous blood samples, whereas intermediate measurement precision was assessed using control solution samples. Standard deviation (SD) and coefficient of variation (CV) were calculated for glucose concentrations <100 mg/dl and ⩾100 mg/dl, respectively. Precision acceptance criteria are not specified by ISO 15197:2013. RESULTS: All three BGMS fulfilled system accuracy criteria with 96% to 98% of individual test strip lot's results falling within the acceptable accuracy limits. All measurement results fell within CEG zones A and B. For measurement repeatability, SD was ⩽3.3 mg/dl, and CV was ⩽3.9% for the investigated BGMS. Assessment of intermediate measurement precision showed SD ⩽1.3 mg/dl and CV ⩽3.0%. CONCLUSION: All three BGMS fulfilled system accuracy criteria of ISO 15197:2013. In absence of acceptance criteria, precision results were found to be consistent with the manufacturer's labeling of the investigated devices.

Accuracy of five systems for self-monitoring of blood glucose in the hands of adult lay-users and professionals applying ISO 15197:2013 accuracy criteria and potential insulin dosing errors.

OBJECTIVE: In this study, accuracy in the hands of intended users was evaluated for five self-monitoring of blood glucose (SMBG) systems based on ISO 15197:2013, and possibly related insulin dosing errors were calculated. In addition, accuracy was assessed in the hands of study personnel. METHODS: For each system (Accu-Chek 1 Aviva Connect [A], Contour 2 Next One [B], FreeStyle Freedom Lite 3 [C], GlucoMen 4 areo [D] and OneTouch Verio 5 [E]) one test strip lot was evaluated as required by ISO 15197:2013, clause 8. Number and percentage of SMBG measurements within ±15 mg/dl and ±15% of the comparison measurements at glucose concentrations <100 mg/dl and ≥100 mg/dl, respectively, were calculated. In addition, data is presented in surveillance error grids, and insulin dosing errors were modeled. The study was registered at ClinicalTrials.gov (NCT03033849). RESULTS: Four systems (A, B, C, D) fulfilled the tested reagent system lot ISO 15197:2013 accuracy criteria with the tested reagent system lot with at least 95% (lay-users) and 99.5% (study personnel) of results within the defined limits. Measurements with all five systems were within the clinically acceptable zones of the consensus error grid and the surveillance error grid. Median modeled insulin dosing errors were between -0.8 and +0.6 units for measurements performed by lay-users and between -0.7 and +0.8 units for study personnel. Frequent lay-user errors were not checking the test strips' expiry date, applying blood incorrectly and handling the device incorrectly. CONCLUSION: In this study, the systems showed slight differences in the number of results within ISO 15197:2013 accuracy limits. Inaccurate SMBG measurements can result in insulin dosing errors and adversely affect glycemic control.

Proof of Concept Study to Assess the Influence of Oxygen Partial Pressure in Capillary Blood on SMBG Measurements.

BACKGROUND: Measurement results provided by blood glucose monitoring systems (BGMS) can be affected by various influencing factors. For some BGMS using glucose oxidase (GOx)-based test strips, one of these factors is the oxygen partial pressure (pO2) of the applied blood sample. Because assessing the potential influence of pO2 when measuring capillary blood samples is not straight-forward, we performed a proof of concept study. METHOD: Influence of pO2 was investigated for two GOx-based BGMS (BGMS A and B). Measurement results of the GOx-based BGMS were compared with measurement results from a pO2-independent BGMS (BGMS C). A total of 119 samples from 60 subjects were measured, twice with BGMS C, then 6 times each with BGMS A and BGMS B or vice versa, and again twice with BGMS C. Immediately afterward, pO2 was determined. Linear regression analysis based on relative differences between results from BGMS A or BGMS B and results from BGMS C was performed to estimate the degree of pO2 influence. RESULTS: The relative bias between the lowest and highest pO2 values differed by 14.3% for BGMS A, indicating a pO2 influence that might be clinically relevant, and by 9.7% for BGMS B, indicating that pO2 influence may be too small to be reliably detected because of the BGMS' imprecision. CONCLUSIONS: This proof of concept study showed that with the procedures used, a potentially clinically relevant influence of pO2 in capillary blood samples on GOx-based BGMS could be detected. Further larger-scale studies are needed to verify this influence.