Today, innovative systems for self-monitoring of blood glucose (SMBG) involve new technologies, for example, connectivity to mobile phones, with the aim to facilitate the management of diabetes. For adequate therapeutic decisions the accuracy of blood glucose (BG) measurement results obtained with an SMBG system is crucial. The International Organization for Standardization (ISO) standard 15197:20131 is widely accepted for the accuracy assessment of SMBG systems. ISO 15197:2013 was harmonized in the European Union as EN ISO 15197:2015 with no changes regarding its requirements. According to ISO 15197:2013, at least 95% of the system’s results shall fall within ±15 mg/dl of the results of the comparison method at BG concentrations <100 mg/dl and within ±15% at BG concentrations ≥100 mg/dl; and 99% of the results shall be within zones A and B of the consensus error grid (CEG).
In this study, accuracy of a new system was evaluated with three different test strip lots based on testing procedures and system accuracy criteria of ISO 15197:2013.
The OneTouch Verio Flex™ system (LifeScan Europe, Division of Cilag GmbH International, Zug, Switzerland) has been recently introduced into the market. The device uses an optimized algorithm to further improve low glucose accuracy and has Bluetooth® Smart (Bluetooth SIG, Inc, Kirkland, WA, USA) function to connect with a compatible wireless device. In addition, the device provides a color range indicator (ColorSure™ technology (Johnson & Johnson, New Brunswick, NJ, USA) to facilitate the interpretation of BG measurement results (low, in-range, high).
The study was performed between March and April 2017 in compliance with the German Medical Devices Act at the Institut für Diabetes-Technologie Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm, Ulm, Germany. The study protocol was approved by the Ethics Committee and the Federal Institute for Drugs and Medical Devices.
Meter and reagent system lots were provided by LifeScan Scotland Limited (Inverness, Scotland, UK) who reconfigured the meters to enable the download of transient data at the end of each study day with specific software. Each test strip lot was tested on 100 capillary blood samples from different subjects (≥18 years, diabetes type 1 or type 2) based on testing procedures of ISO 15197:2013. Comparison measurements were performed on capillary plasma with a glucose oxidase laboratory method (YSI 2300 STAT Plus™ glucose analyzer, YSI Incorporated, Yellow Springs, OH, USA). Regular internal and external quality control measures were performed to confirm trueness and precision of the comparison method.
The system fulfilled with all three tested reagent system lots accuracy criteria of ISO 15197:2013 with 99.5% to 100% of results within the required limits (±15 mg/dl or ±15%) and 100% of results within CEG zones A and B (Table 1). Between 95.5% and 98% of measurement results were within ±10 mg/dl or ±10% of the comparison measurements.
Table 1.
System Accuracy Results According to ISO 15197:2013 and Relative Bias According to Bland and Altman.2
| # | Lot | ISO 15197:2013 system accuracy |
Bias | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Percentage and number of results within | ||||||||||||
| Glucose concentrations <100 mg/dl |
Glucose concentrations ≥100 mg/dl |
Consensus error grid zones A and B | ||||||||||
| ±15 mg/dl & ±15% | ±10 mg/dl & ±10% | ±5 mg/dl & ±5% | ±15 mg/dl | ±10 mg/dl | ±5 mg/dl | ±15% | ±10% | ±5% | ||||
| 1 | 4146677 |
100%
200/200 |
96.5% 193/200 |
70% 140/200 |
100% 62/62 |
98.4% 61/62 |
56.5% 35/62 |
100% 138/138 |
95.7% 132/138 |
76.1% 105/138 |
100%
600/600 |
−3.2% |
| 2 | 4146678 |
99.5%
199/200 |
95.5% 191/200 |
63.5% 127/200 |
98.4% 61/62 |
98.4% 61/62 |
61.3% 38/62 |
100% 138/138 |
94.2% 130/138 |
64.5% 89/138 |
−4.0% | |
| 3 | 4146679 |
99.5%
199/200 |
98% 196/200 |
72% 144/200 |
100% 62/62 |
98.4% 61/62 |
80.6% 50/62 |
99.3% 137/138 |
97.8% 135/138 |
68.1% 94/138 |
−2.0% | |
For each lot, 200 data points (duplicate measurements on a sample) were included. Bold text indicates that the system fulfilled with the tested reagent system lots ISO 15197:2013 accuracy criteria (at least 95% of results within ±15 mg/dl / ±15% and at least 99% of results within CEG zones A and B).
The new system showed a high level of measurement accuracy and fulfilled with all three tested lots ISO 15197:2013 accuracy criteria. In bias analysis, only minor variations between the 3 evaluated reagent system lots were observed.
Footnotes
Abbreviations: BG, blood glucose; CEG, consensus error grid; ISO, International Organization for Standardization; SMBG, self-monitoring of blood glucose.
Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: All authors are employees of the Institut für Diabetes-Technologie Forschungs- und Entwicklungsgesellschaft mbH an der Universität Ulm (IDT), Ulm, Germany. GF is general manager of the IDT, which carries out clinical studies on the evaluation of BG meters and medical devices for diabetes therapy on its own initiative and on behalf of various companies. GF/IDT have received speakers’ honoraria or consulting fees from Abbott, Ascensia, Bayer, Berlin-Chemie, Becton-Dickinson, Dexcom, LifeScan, Menarini Diagnostics, Novo Nordisk, Roche, Sanofi, Sensile, and Ypsomed.
Funding: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by a grant from LifeScan Scotland Limited, Inverness, Scotland, United Kingdom.
References
- 1. International Organization for Standardization. In vitro diagnostic test systems—requirements for blood-glucose monitoring systems for self-testing in managing diabetes mellitus. ISO 15197:2013. [Google Scholar]
- 2. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;1:307-310. [PubMed] [Google Scholar]