Abstract
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.
Keywords: bias, self-monitoring of blood glucose, ISO 15197, linear regression, system accuracy, user performance
Introduction
Blood glucose monitoring systems (BGMSs) are a cornerstone in diabetes management, especially for insulin-treated patients with diabetes mellitus type 1 (T1DM) and type 2 (T2DM).1-4 Their use has the potential to prevent late complications,1,5 facilitate insulin dose adjustment, eg, after meal consumption or before physical activity,4,6 and help to avoid dangerous hypo- and hyperglycemic metabolic conditions caused by, eg, inappropriate insulin dosing. In this context, BGMSs have to provide sufficiently accurate results in the hands of lay users.
The International Organization for Standardization (ISO) standard ISO 15197:2013 7 defines accuracy requirements for BGMSs, including a system accuracy assessment (ISO 15197, clause 6.3) and a user performance evaluation (ISO 15197, clause 8). While the system accuracy assessment focuses on the performance of BGMSs under laboratory conditions in the hands of trained personnel, the user performance evaluation is concerned with assessing whether intended users are able to obtain accurate blood glucose (BG) measurement results.
Studies have shown that color coding of BG results can help users to interpret and categorize their glucose values, to correctly determine their glycemic risk, and to identify a suitable course of action more quickly.8-14 Furthermore, it enables healthcare professionals an easier assessment of glycemic control. As a result, not only metabolic parameters and glycemic control of patients with diabetes improve, but also their diabetes management performance and satisfaction.13,15-17
The aim of this study was a system accuracy assessment and a user performance evaluation of four BGMSs with color coding of BG results.
Methods
This study was performed in two parts between March and May 2022 at the Institut für Diabetes-Technologie Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm (IfDT), Ulm, Germany, in compliance with the German Medical Devices Act, the Guideline for Good Clinical Practice and under consideration of the Declaration of Helsinki. First, user performance evaluation was conducted, followed by the assessment of system accuracy. The study protocol was approved by the responsible Ethics Committee (“Ethikkommission bei der Landesärztekammer Baden-Württemberg”), approval number MP-2015-009, and exempted from approval by the competent authority. The study was registered at the German Clinical Trials Register (DRKS; registry numbers DRKS00028602 and DRKS00028604). Prior to study start, all participants signed informed consent forms. Experimental procedures were performed based on the requirements described in detail in ISO 15197:2013, clause 6.3 and clause 8. 7
Participants
Subjects were examined by a physician to check eligibility after they signed the informed consent form. To that end, the subjects’ anamnesis, including medication and interfering substances indicated in the respective manufacturer’s labeling, and eligibility criteria for study participation were checked. For each study part, 100 participants were required according to ISO 15197.
Number and demographic data of included participants for the two study parts are listed in Table 1. According to their own statement, participants of the user performance evaluation had not used the BGMSs being evaluated in the last 3 years.
Table 1.
Demographic Data of Participants.
| User performance evaluation (n = 112) |
System accuracy assessment (n = 113) |
|
|---|---|---|
| Type of diabetes | ||
| Type 1 | 63 (56.3%) | 38 (33.6%) |
| Type 2 | 49 (43.8%) | 48 (42.5%) |
| No diabetes | n.a. | 27 (23.9%) |
| Gender | ||
| Female | 58 (51.8%) | 59 (52.2%) |
| Male | 54 (48.2%) | 54 (47.8%) |
| Age, y | 59.4 ± 12.9 [25-78] | 59.2 ± 14.4 [19-82] |
| Highest education level | ||
| Secondary education | 70 (62.5%) | n.d. a |
| University entrance diploma | 20 (17.9%) | n.d. a |
| University degree | 22 (19.6%) | n.d. a |
| ≥1 blood glucose measurement per week | 104 (92.9%) | n.d. a |
Data provided as numbers and rate of occurrences except for age, which is given as mean ± standard deviation [range].
Abbreviations: n.a., not applicable; n.d., not documented.
Highest education level and blood glucose measurement frequency were only documented for subjects who also participated in the user performance evaluation, but not those who only participated in the system accuracy assessment.
Blood Glucose Monitoring Systems
Four BGMSs with color coding of BG results were evaluated in this study (Table 2). The systems are hereinafter referred to by their study codes A, B, C, and D. Meters, reagent systems (test strips/test tips), and control solutions were purchased from a local pharmacy. All systems displayed plasma-equivalent glucose concentrations and were stored, adjusted, and used according to the respective manufacturers’ labeling. This included monitoring of room temperature and humidity, which were documented in parallel to all BG measurements in the study. The proper functioning of each system was ensured at least once per day with control measurements according to the manufacturers’ labeling prior to the test procedures. For user performance evaluation, control measurements were also performed retrospectively after the familiarization by the lay user and the measurement procedure to confirm the proper function of the systems.
Table 2.
Blood Glucose Monitoring System Characteristics According to the Respective Manufacturer’s Labeling.
| Study code | System | Reagent system | Manufacturer’s comparator method | Reagent unit enzyme | Manufacturer | |
|---|---|---|---|---|---|---|
| Lots | Expiry date | |||||
| A | Accu-Chek Instant | 301651
a
301726 301588 |
2023-09-15 2023-10-20 2023-06-08 |
HK | GDH | Roche Diabetes Care GmbH, Germany |
| B | Contour Next | DP1JPEG09A
a
DP1JPEF04C DP1KPEG10A |
2023-09 2023-09 2023-10 |
GOD | GDH | Ascensia Diabetes Care Holdings AG, Switzerland |
| C | Medisafe Fit Smile | 21080118
a
21080217 21090217 |
2023-01 2023-01 2023-02 |
GOD | GOD | Terumo Corporation, Japan |
| D | OneTouch Ultra Plus Reflect | 4819927
a
4824027 4815142 |
2023-09 2023-09 2023-08 |
GOD | GDH | LifeScan Europe GmbH, Switzerland |
Abbreviations: HK, hexokinase; GDH, glucose dehydrogenase; GOD, glucose oxidase.
These lots were used for system accuracy and user performance evaluation.
Participant’s capillary blood hematocrit value was determined.
Comparator Methods
Comparator measurements were performed for each test system with a hexokinase (HK)-based method (Cobas Integra 400 Plus; Roche Instrument Center, Rotkreuz, Switzerland) and (approx. one-third of samples) with a glucose oxidase (GOD)-based method (YSI 2300 STAT Plus glucose analyzer; YSI Incorporated, Yellow Springs, Ohio).
Metrological traceability of both comparator analyzers was assured by the respective analyzer’s manufacturer. Daily quality control measurements following instructions for use and IfDT-internal standard operating procedures were performed using higher-order control materials (NIST SRM 965b [National Institute of Standards and Technology, Gaithersburg, MD, USA]). Using the four available glucose concentration levels, the HK and GOD analyzers exhibited bias of ≤2.2% and ≤2.2%, respectively, and coefficients of variation of ≤1.6% and ≤1.9%, respectively. In addition, both analyzers successfully participated in an external quality assessment scheme (round-robin test). Comparator measurements with both procedures were performed in duplicate on capillary plasma samples.
To enable ISO 15197-based assessments of the measurement accuracy of BGMSs whose manufacturer’s reference method is GOD-based, the HK-based analyzer’s comparator results were converted into comparator results equivalent to results of the GOD-based analyzer (hereinafter named GOD analyzer-equivalent results). For recalibration of HK analyzer comparator data, a method comparison of the HK and the GOD analyzers was performed using a linear regression according to Passing and Bablok.18,29 This method comparison only included those samples, for which valid results from both methods were available. Using the slope and intercept of the equation obtained by linear regression (see Supplemental Figure 1), all HK analyzer comparator results were converted to GOD analyzer-equivalent comparator results.
Samples for comparator measurements were collected in lithium heparin tubes and centrifuged within ten minutes of collection to obtain plasma. Plasma was separated immediately after centrifugation. Samples were measured within less than 30 minutes after plasma separation. Before the study personnel’s measurements with each BGMS and before each aliquot collection for comparator measurements, a fresh blood drop was generated.
Study Procedures—User Performance Evaluation
Participants were allowed to review the instructions for use provided with the system and to perform up to three training measurements with control solution. No additional instructions regarding BGMS handling, training, or assistance were provided and the familiarization was supervised by study personnel to prevent any influence on a participant, eg, by other participants.
Afterward, participants performed BG measurements under observation by study personnel, who documented handling errors based on the description in the system-specific instructions for use. Errors registered only by the study personnel but not by the participants did not lead to exclusion of measurements from accuracy analysis. If participants stated that they had performed the measurement incorrectly, up to three repetitions were allowed. Study personnel subsequently collected two samples for comparator measurements, if no mistakes were reported by the participant, or if the participant had performed their third repetition. The result of the first comparator sample was used as reference value for the user’s BG measurement, whereas the second sample was used to check for glucose stability. After their BG measurements, participants were asked to complete a BGMS-specific questionnaire, and, after completion of measurements with all four BGMSs, a general questionnaire regarding color coding of BG results.
All participants used the same reagent system lot for a specific BGMS, and each participant completed measurements with one BGMS before using the next BGMS. Each of the four BGMSs was used by all participants, but the order in which the systems were used was rotated between participants to minimize a potential sequence effect. If participants did not wash and dry their hands of their own accord before performing BG measurements, they were asked to do so. All reminders were documented.
Study Procedures—System Accuracy Assessment
This assessment was performed based on ISO 15197, clause 6.3, 7 including distribution of glucose concentrations and use of three different reagent system lots. Samples for comparator measurements were obtained before and after measurements with the BGMS. The mean result of HK analyzer results for these two samples was used to categorize samples with respect to the distribution of glucose concentrations. For the system accuracy assessment versus GOD analyzer-equivalent results, the results of the same samples were used independent of their distribution. Because insufficient numbers of samples were obtained for glucose concentration categories ≤50 mg/dL, >50 to ≤80 mg/dL, and >400 mg/dL, glucose concentrations were manually adjusted in five, one, and two samples, respectively, in accordance with ISO 15197. Low glucose concentrations were obtained through glycolysis, whereas high concentrations were achieved by supplementation with glucose stock solution. Samples with adjusted glucose concentrations were applied to the BGMS with a syringe. In adjusted samples, the partial pressure of oxygen (pO2) was checked to be similar to that found in native capillary samples by using a blood gas analyzer (Opti Check; OPTI Medical Systems Incorporation, Roswell, Georgia). 19
Statistical Analysis
For user performance evaluation and for system accuracy assessment, 100 and 3 × 200 data points, respectively, were obtained from 100 capillary samples from different participants. Participants from whom samples were included in the analysis of the individual BGMS varied between systems. Data were excluded from analysis for the following reasons: (1) comparator method quality control result outside the specified limits; (2) difference between the first and second comparator measurements exceeded the acceptance criteria for sample stability; (3) hemolysis in plasma samples for comparator measurements; (4) pO2 of adjusted samples outside desired limits; (5) procedural error. Furthermore, data were excluded if 100 valid measurements (for user performance evaluation) or the required number of samples in a BG concentration range (system accuracy assessment) was reached.
In this study, accuracy limits of ISO 15197 and consensus error grid (CEG) analysis were applied and accuracy was evaluated for each BGMS by comparison of its measurement results to HK analyzer or GOD analyzer-equivalent results. The comparison with HK analyzer results served as the primary analysis. In addition, further analyses were performed, including bias and linear regression,18,20 as well as the minimal deviation from the respective comparator method’s results within which ≥95% of results of the BGMS were found and the mean absolute relative difference (MARD) as described elsewhere.21,22
Results
Measurement Accuracy
Results regarding the measurement accuracy of the four BGMSs in comparison with HK analyzer results are provided in Tables 3 and 4. All systems achieved ≥95% of results within ±15 mg/dL or ±15% of the comparator results with each individual reagent lot, both in the hands of lay users and trained study personnel. Figure 1 presents the measurement accuracy data in a difference plot. For all systems, 100% of results were found within clinically acceptable zones A and B of the CEG. Qualitative differences were found regarding more stringent accuracy limits of ±10 mg/dL/±10% and ±5 mg/dL/±5%, as well as regarding MARD and the range in which 95% of results were found. Figure 2 displays bias and 95% limits of agreement for all systems and both study parts, indicating small lot-to-lot variability within BGMSs (<5%) and, to some degree, systematic differences in bias between study parts.
Table 3.
Percentage of Results Within ISO 15197:2013 Accuracy Criteria (Clause 6.3 and 8) 7 for Each Lot and Minimal Deviation From the HK Analyzer Results Containing at Least 95% of Values.
| System # | Part a | Percentage of blood glucose monitoring system results within specified deviation of the HK analyzer result |
Minimal deviation within which 95% of results were found (mg/dL or %) | ||
|---|---|---|---|---|---|
| ±15 mg/dL / ±15% | ±10 mg/dL / ±10% | ±5 mg/dL / ±5% | |||
| A | 1 | 99 | 98 | 73 | 8.7 |
| 2 | 100 | 96.5 | 64.5 | 10.6 | |
| 100 | 97 | 62.5 | |||
| 100 | 84 | 34 | |||
| B | 1 | 100 | 98 | 71 | 8.7 |
| 2 | 100 | 100 | 96 | 5.3 | |
| 100 | 100 | 93 | |||
| 100 | 100 | 93 | |||
| C | 1 | 100 | 94 | 54 | 10.4 |
| 2 | 100 | 100 | 80 | 8.0 | |
| 100 | 96 | 73.5 | |||
| 100 | 99 | 80 | |||
| D | 1 | 95 | 81 | 36 | 14.5 |
| 2 | 98.5 | 88.5 | 48.5 | 11.0 | |
| 99 | 96 | 68 | |||
| 99 | 93.5 | 59 | |||
Abbreviation: HK, hexokinase.
Part 1: user performance evaluation, part 2: system accuracy assessment.
Table 4.
Results of Bias and 95% Limits of Agreement (±1.96 × Standard Deviation) According to Bland and Altman, 20 Linear Regression According to Passing and Bablok, 18 and MARD, Based on Comparison With HK Analyzer Results for Each Lot.
| System # | Part a | Bland-Altman | Passing-Bablok slope | MARD, % | |
|---|---|---|---|---|---|
| Rel. bias, % | 95% limits of agreement, % | ||||
| A | 1 | −2.4 | −10.9 to +6.1 | 0.96 | 3.9 ± 2.9 |
| 2 | −4.4 | −11.0 to +2.2 | 0.93 | 4.5 ± 2.9 | |
| −4.4 | −10.9 to +2.1 | 0.93 | 4.5 ± 2.9 | ||
| −7.1 | −13.8 to −0.4 | 0.90 | 6.9 ± 3.1 | ||
| B | 1 | −3.4 | −10.0 to +3.3 | 0.96 | 3.8 ± 2.6 |
| 2 | −0.8 | −6.3 to +4.7 | 0.98 | 2.3 ± 1.7 | |
| −1.4 | −6.5 to +3.8 | 0.96 | 2.4 ± 1.6 | ||
| −0.9 | −6.5 to +4.8 | 0.97 | 2.3 ± 1.8 | ||
| C | 1 | −4.6 | −12.4 to +3.3 | 0.92 | 4.9 ± 3.2 |
| 2 | −1.7 | −9.2 to +5.7 | 0.96 | 3.4 ± 2.4 | |
| −3.1 | −11.2 to +5.0 | 0.95 | 4.1 ± 2.9 | ||
| −1.2 | −9.0 to 6.6 | 0.96 | 3.3 ± 2.4 | ||
| D | 1 | −5.7 | −18.4 to +7.0 | 0.92 | 6.9 ± 4.4 |
| 2 | −5.6 | −15.0 to +3.8 | 0.93 | 6.0 ± 3.7 | |
| −2.9 | −12.5 to +6.8 | 0.96 | 4.5 ± 3.3 | ||
| −4.5 | −13.3 to +4.3 | 0.95 | 5.0 ± 3.4 | ||
Abbreviations: MARD, mean absolute relative difference; HK, hexokinase.
Part 1: user performance evaluation, part 2: system accuracy assessment.
Figure 1.
Difference plots for the investigated systems versus HK analyzer results from the hexokinase method. Blue: data for user performance evaluation (study part 1), green: data for system accuracy assessment (study part 2). Squares, triangles, and crosses indicate the three different reagent system lots used (see also Table 2). ISO 15197 accuracy limits are displayed as black solid lines. Abbreviation: HK, hexokinase.
Figure 2.
Relative bias versus HK analyzer results and 95% limits of agreement according to Bland and Altman for each lot. 20 Blue: data for user performance evaluation (study part 1), green: data for system accuracy assessment (study part 2). Abbreviation: HK, hexokinase.
Results from the analysis using GOD analyzer-equivalent results can be found in the supplemental data.
Human Factors and Questionnaires
Handling errors made by the participants that were documented by study staff are shown in Table 5.
Table 5.
Number of Handling Errors as Documented by the Study Staff.
| Description | System | |||
|---|---|---|---|---|
| A | B | C | D | |
| Error inserting reagent system | 0 | 0 | 0 | 4 |
| Inadequate blood drop | 1 | 0 | 3 | 3 |
| Blood application in wrong place | 5 | 0 | 0 | 14 a |
| Insufficient amount of blood | 0 | 0 | 0 | 3 |
| Finger pressed on reagent system or touched/moved during measurement | 1 | 6 | 4 | 4 |
| Test strip not removed from blood drop after device started measurement | 2 | 1 | 0 | 0 |
| Prohibited re-dosing/intermittent blood application | 3 | — b | 6 | 6 |
| Other errors | 1 | 1 | 1 | 1 |
| Unable to generate quantitative result | 0 | 0 | 0 | 11 a |
Blood application in the wrong place resulted in some participants being unable to obtain a quantitative result. In five of these 11 cases, an error message indicating a test strip fill problem was displayed.
System B allows application of additional blood within 60 seconds.
Most participants agreed or completely agreed that manuals provided with the system were clear and appropriate; this comprised instructions for use (88% agreement rate), quick reference guide (94%), and reagent system package insert (84%), with only small differences between the systems. The systems were rated to be easy to use by 99% (system A), 96% (systems B and D), and 80% (system C) of participants.
While 84% of participants agreed that color coding of results helps identifying current glucose levels, only 49% of them indicated that color coding would be a selection criterion for their next BGMS purchase. Regarding coloring schemes, 88% of participants stated that systems from different manufacturers should use the same colors for low, normal, and high glucose values. However, no clear preference was revealed regarding the specific coloring schemes of the four investigated BGMSs, as 31%, 20%, 24%, and 25% of participants favored the coloring scheme implemented by system A, B, C, and D, respectively.
Discussion
In this study, measurement accuracy of four BGMSs was assessed when used by lay users and by trained study personnel. Lay users’ measurement attempts were observed by study personnel to identify potential handling mistakes. System-specific questionnaires about clarity and appropriateness of manufacturer labeling as well as ease of use were completed by lay users, as was a questionnaire about color coding of BG results in general.
All systems showed ≥95% of results within ±15 mg/dL or ±15% deviation from comparator method results, thus meeting ISO 15197 accuracy requirements with the investigated reagent system lots with only small differences between them. The level of accuracy, at least with respect to this deviation limit, achieved in the hands of lay users was similar to that in the hands of trained personnel. The observed systematic differences in bias between user performance evaluation and system accuracy assessment could have been caused by different operators, but they are more likely affected by the differences in glucose concentration distribution between the defined distribution for system accuracy assessments and the lack of requirements for user performance evaluation. Any BG concentration-dependent effects may therefore affect the results from the two study parts differently. Another potential factor is a locally reduced glucose concentration in the subcutaneous tissue at the peripheral site of the fingerstick compared with larger capillary blood vessels. In the user performance evaluation, participants immediately sampled a small drop of blood for the BG measurement, whereas a comparably large volume with blood replenished from larger capillaries was drawn for the comparator measurement (approx. 200 µL of capillary blood) before any BG measurements in the system accuracy assessment.
When applying more stringent deviation limits of ±10 mg/dL or ±10% and ±5 mg/dL or ±5%, which are also recommended by ISO 15197 to be reported, substantial differences between systems become more apparent. Depending on the specific analyzer used for comparison, the investigated BGMS showed highly accurate results, with two BGMS exhibiting MARD values below 3%.
Although none of the participants in the user performance evaluation had used any of the devices for at least the three previous years, most participants were experienced in the performance of BG measurements (≥1 measurement per week). In this study, pressing the finger against the reagent system unit and intermittent blood application were two of the most common lay-user mistakes observed by the study personnel.
For system D, eight participants performed multiple measurements before obtaining a valid result, which was linked to incorrect application of blood. The shape of the test strips likely contributed to this high rate of occurrence: For system D, blood has to be applied on the left or right edge of the test strip, as opposed to systems A and B, which also use test strips, where blood has to be applied to the tip of the strips. In this study, participants had been given only limited time for self-training, while self-training through repeated use likely reduces the rate of occurrence.
System C was perceived as having comparably low ease of use, with 80% of participants agreeing that it was easy to use as opposed to >95% agreement for the other systems. However, this result is likely influenced by the system’s design, as it does not use traditional test strips, and repeated use would likely lead to a higher perceived ease of use.
The results of the user performance evaluation indicate that manufacturers should ensure not only that their BGMS are accurate, but also that they are sufficiently easy to use.
While participants had no clear favorite regarding color coding of BG results among the systems used in the study, the majority stated that all systems should follow the same coloring scheme. This was not the case for the systems used in the study. Systems A and B coded low BG results with red color, whereas systems C and D used blue color for low BG values. In contrast, blue color was used by system A to indicate high BG values. High values were coded with amber color by system B, amber, pink, and red colors by system C (depending on the specific glucose concentration), and red color by system D. Ideally, all BGMSs should use the same coloring scheme for various glucose levels as it has been recommended for continuous glucose monitoring (CGM) systems, and it is used in the ambulatory glucose profile for both CGM systems and BGMS.23,24 This is important from a safety point of view as it would help to avoid confusion, and would not necessitate healthcare professionals to be aware of manufacturer-specific differences of coloring of various glucose levels when assessing glycemic control and making decisions with their diabetes patients.
The use of inaccurate BGMSs is associated with increased healthcare costs, 25 and inaccuracy has a relevant effect on clinical outcomes when therapy is guided by BGMSs or by manually calibrated CGM systems.26,27 While all BGMSs in this study met ISO 15197 accuracy requirements, previous studies indicated that this may not be the case for all systems available on the market.21,28 Care should be taken in the selection of BGMSs so that persons with diabetes can use an accurate BGMS that they find easy to use.
Conclusions
The four BGMSs evaluated in this study showed only small differences in measurement accuracy, and they all were found to meet ISO 15197:2013 accuracy requirements both in the hands of lay users and trained study personnel, with only small differences between them. More marked differences were found when applying more stringent accuracy limits. Handling errors made by the users, as observed by study personnel, differed between the systems. Pressing the finger against the reagent system unit, incorrect blood application onto the reagent system, and intermittent blood application were frequently observed. These results indicate that manufacturers should not neglect ease of use. While most participants indicated that different manufacturers should use the same scheme for color coding of results, there was no clear favorite among the four assessed BGMSs.
Supplemental Material
Supplemental material, sj-docx-1-dst-10.1177_19322968221141926 for User Performance Evaluation and System Accuracy Assessment of Four Blood Glucose Monitoring Systems With Color Coding of Measurement Results by Stefan Pleus, Annette Baumstark, Sebastian Schauer, Julia Kölle, Nina Jendrike, Jochen Mende, Cornelia Haug and Guido Freckmann in Journal of Diabetes Science and Technology
Acknowledgments
The authors would like to thank the participants of the study as well as the study staff.
Footnotes
Abbreviations: BG, blood glucose; BGMS, blood glucose monitoring system; GOD, glucose oxidase; HK, hexokinase; ISO, International Organization for Standardization; MARD, mean absolute relative difference.
The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: GF is general manager and medical director of the IfDT (Institut für Diabetes-Technologie Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm, Ulm, Germany), which carries out clinical studies on the evaluation of BGMS, CGMS and other diabetes technology on its own initiative and on behalf of various companies. GF/IfDT have received speakers’ honoraria or consulting fees from Abbott, Ascensia, Berlin Chemie, Beurer, BOYDSense, CRF Health, Dexcom, i-SENS, Lilly, Metronom, MySugr, Novo Nordisk, Pharmasens, Roche, Sanofi, Sensile, Terumo, and Ypsomed.
SP, AB, SS, JK, NJ, JM, and CH are employees of the IfDT.
Funding: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This investigator-initiated study and medical writing were financially supported by Ascensia Diabetes Care Holdings AG, Switzerland, through an unrestricted grant.
Clinical Trial Number: German Clinical Trials Register (DRKS) registry numbers: DRKS00028602 and DRKS00028604.
ORCID iDs: Stefan Pleus 
https://orcid.org/0000-0003-4629-7754
Annette Baumstark
https://orcid.org/0000-0002-3439-7400
Sebastian Schauer
https://orcid.org/0000-0002-9873-0989
Jochen Mende
https://orcid.org/0000-0001-8667-760X
Guido Freckmann
https://orcid.org/0000-0002-0406-9529
Supplemental Material: Supplemental material for this article is available online.
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Supplementary Materials
Supplemental material, sj-docx-1-dst-10.1177_19322968221141926 for User Performance Evaluation and System Accuracy Assessment of Four Blood Glucose Monitoring Systems With Color Coding of Measurement Results by Stefan Pleus, Annette Baumstark, Sebastian Schauer, Julia Kölle, Nina Jendrike, Jochen Mende, Cornelia Haug and Guido Freckmann in Journal of Diabetes Science and Technology