Performance of two updated blood glucose monitoring systems: an evaluation following ISO 15197:2013

Analysis of "Capillary and Venous Blood Glucose Accuracy in Blood Glucose Meters Versus Reference Standards: The Impact of Study Design on Accuracy Evaluations"

The article by Macleod and coauthors outlines an accuracy study of two blood glucose monitoring systems (BGMSs) against glucose-oxidase- and hexokinase-based assays showing how the reference/comparison method and inappropriate sample comparisons can affect accuracy conclusions. The dangers of independent institutions producing inappropriate conclusions when the methodology used for product regulatory or registration accuracy requirements is not according to best practice are stressed. The authors highlight several important aspects of a multistep accuracy evaluation protocol. However, it is essential that anyone undertaking or reporting BGMS accuracy studies should have a clear understanding of each and every protocol point, best practice, and how each can influence accuracy conclusions. Claims against regulatory accuracy criteria should be made only if the detailed specified protocol design and analysis is followed.

A Review of Blood Glucose Monitor Accuracy

The aim of this study was to assess the accuracy of blood glucose monitors (BGMs) from studies reported in the medical literature. A literature review was performed of publications between 2010 and 2017 that presented data about the accuracy of BGMs using ISO 15197 2003 and/or ISO 15197 2013 as target standards. We found 58 publications describing the performance of 143 unique BGM systems, 59 of which were Food and Drug Administration (FDA) cleared. When compared with non-FDA-cleared BGMs, FDA-cleared BGMs were significantly more likely to pass both ISO 15197 2003 (OR = 2.39, CI 1.45-3.92, P < 0.01) and ISO 15197 2013 standards (OR = 2.20, CI 1.51-3.27, P < 0.01). Newer meters were more likely to pass both ISO 15197 2003 and ISO 15197 2013 standards. Many of the studies were supported by BGM manufacturers, and when compared with independent studies, an FDA-cleared BGM was significantly more likely to pass in a manufacturer-supported study for both ISO 15197 2003 (OR = 22.4, CI 8.73-21.57, P < 0.001) and ISO 15197 2013 (OR = 23.08, CI 10.16-60.03, P < 0.001). BGM accuracy should be assessed independently following regulatory clearance to ensure accurate performance. Failure to meet performance levels mandated by standards can result in deleterious clinical and economic effects.

Enzyme-Based Glucose Sensor: From Invasive to Wearable Device

Blood glucose concentration is a key indicator of patients' health, particularly for symptoms associated with diabetes mellitus. Because of the large number of diabetic patients, many approaches for glucose measurement have been studied to enable continuous and accurate glucose level monitoring. Among them, electrochemical analysis is prominent because it is simple and quantitative. This technology has been incorporated into commercialized and research-level devices from simple test strips to wearable devices and implantable systems. Although directly monitoring blood glucose assures accurate information, the invasive needle-pinching step to collect blood often results in patients (particularly young patients) being reluctant to adopt the process. An implantable glucose sensor may avoid the burden of repeated blood collections, but it is quite invasive and requires periodic replacement of the sensor owing to biofouling and its short lifetime. Therefore, noninvasive methods to estimate blood glucose levels from tears, saliva, interstitial fluid (ISF), and sweat are currently being studied. This review discusses the evolution of enzyme-based electrochemical glucose sensors, including materials, device structures, fabrication processes, and system engineering. Furthermore, invasive and noninvasive blood glucose monitoring methods using various biofluids or blood are described, highlighting the recent progress in the development of enzyme-based glucose sensors and their integrated systems.

Strengths and Limitations of New Approaches for Graphical Presentation of Blood Glucose Monitoring System Accuracy Data

Graphical presentation of blood glucose monitoring systems' (BGMSs) accuracy typically includes difference plots (DPs). Recently, 3 new approaches were presented: radar plots (RPs), rectangle target plots (RTPs), and surveillance error grids (SEGs). BGMS data were modeled based on 3 scenarios that can be encountered in real life to highlight strengths and limitations of these approaches. Detailed assessment of BGMS data may be easier in plots with individual data points (DPs, RPs, SEGs), whereas RTPs may facilitate display of large amounts of data or comparison of BGMS. SEGs have the advantage of assessing clinical risk. The selection of a specific type depends mostly on the kind of information sought (eg, accuracy in specific concentration intervals, lot-to-lot variability, clinical risk) as there is no "absolute best" approach.

Retrospective Analysis of Continuous Glucose Monitoring Data With the Surveillance Error Grid Supports Nonadjunctive Dosing Decisions

OBJECTIVE

The objective was to assess clinical risks of inaccurate continuous glucose monitoring (CGM) system readings as estimated by the surveillance error grid (SEG).

METHODS

Values from Dexcom G4 Platinum system with an advanced algorithm (Software 505) were plotted on the SEG with temporally matched reference venous (YSI) values collected during clinic visits on days 1, 4, and 7 of sensor wear. Data from a pediatric study (N = 79, age [mean ± SD] 12.2 ± 4.6 years, all with type 1 diabetes) and an adult study (N = 51, age 46.7 ± 15.8 years, 44 with type 1 diabetes and 7 with type 2 diabetes) were used.

RESULTS

Pediatric data included 2262 paired points, of which 1990 (88.0%) were in the "no risk" zone. Adult data included 2263 paired points, of which 2056 (90.9%) were in the "no risk" zone. Performance was best on Day 4, when 92.7% and 93.3% of points from the pediatric and adult studies, respectively, were in the "no risk" zone. Nine of the 4525 points (<0.2%) from 5 different sensors were in zones representing moderate risk, and none were in zones representing great or extreme risk.

CONCLUSIONS

SEG analysis suggests that in pediatric and adult subjects with diabetes, using CGM values for diabetes management poses minimal risk to the user. CGM users also benefit from glucose trends and alerts.

Accuracy Evaluation of Four Blood Glucose Monitoring Systems in the Hands of Intended Users and Trained Personnel Based on ISO 15197 Requirements

BACKGROUND

Self-monitoring of blood glucose (BG) is an integral part in the therapy of people with diabetes, which is why blood glucose monitoring systems (BGMS) have to fulfill minimum accuracy requirements. However, accuracy is often assessed by trained operators, although such assessments do not necessarily allow for drawing conclusions on accuracy in the hands of lay users.

METHODS

The accuracy of 4 different BGMS (Accu-Chek^® Active, Accu-Chek^® Performa, Contour^®Plus, and OneTouch^® SelectSimple™) in the hands of lay users and trained study personnel was assessed in this study. Procedures were based on International Organization for Standardization (ISO) 15197:2013, clause 8, requirements. BGMS measurement results were compared against results from a glucose oxidase and a hexokinase laboratory analyzer. Handling errors made by lay users were documented. Accuracy was evaluated applying ISO 15197:2013/EN ISO 15197:2015 criteria (percentage of results within ±15 mg/dL or ±15%), more stringent criteria (10 mg/dL or 10%, and 5 mg/dL or 5%, respectively), and ISO 15197:2003 system accuracy criteria.

RESULTS

The level of accuracy differed among the four BGMS investigated independent from the operator. One system had less than 95% of the values within each of the limits and one system showed marked differences in accuracy when used by trained personnel and by lay users. Common lay user errors were not checking the test strip codes, incorrect application of blood, and not using the blood drop immediately.

CONCLUSIONS

BGMS accuracy can differ when used by trained personnel and when used by lay users. It is important that BGMS manufacturers provide systems that are as insensitive to operator errors as technically possible and easy to use.