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

Reliability and accuracy of bedside capillary blood glucose measurement by glucometers compared to venous blood glucose in critically ill patients: A facility based cross-sectional study

BACKGROUND

The traditional reference standard, venous blood glucose requires venipuncture and laboratories usually return the test results after 60 min. Our aim was to determine the agreement accuracy of glucose (capillary) levels obtained by POC glucometers with glucose (venous) values by standard laboratory method (glucose-oxidase) and to assess whether and to what extent the glucometers perform uniformly well across the entire range of blood glucose values.

METHODS

We compared the diagnostic accuracy of two-point of care glucometers with laboratory venous glucose, the reference standard using Bland-Altman plots and Clark error grid method to analyse the results.

RESULTS

This study included a total of 110 patients (38[34 %] women; mean age 52.1 years (SD, 17.3); range 14-85 years. Fourteen patients (12 %) were known to have diabetes. The mean glucose value (glucometer 1) was 152.9 mg/dL (SD 83.1); range = 48-501 mg/dL; that by glucometer 2 was 152.2 mg/dL (SD 76.2); range = 30-458 mg/dL and by the laboratory was 148.6 mg/dL (SD 81.5); range = 52-480 mg/dL. Of the 110 subjects, 2(2 %) had blood glucose below 70 mg/dL; 85(77 %) between 70 and 180 mg/dL and 23(21 %) had blood glucose exceeding 180 mg/dL. The Bland-Altman plot showed a bias of 4 mg% (95%CI -9.8 to +1.1); and the limits of agreement were -63 and + 54 mg%. The area under the receiver operating characteristic curve for the two glucometers was 0.92 and 0.93 respectively.

CONCLUSIONS

Point of care glucose, measured by glucometers was in agreement with the venous glucose estimation. Both glucometers were equally accurate and performed uniformly well across the wide range of blood glucose values.

Instrument-free single-step direct estimation of the plasma glucose level from one drop of blood using smartphone-interfaced analytics on a paper strip

We demonstrated an instrument-free miniaturized adaptation of the laboratory gold standard methodology for the direct estimation of plasma glucose from a drop of whole blood using a low-cost single-user-step paper-strip sensor interfaced with a smartphone. Unlike a majority of the existing glucose meters that use whole blood-based indirect sensing technologies, our direct adaptation of the gold-standard laboratory benchmark could eliminate the possibilities of cross interference with other analytes present in the whole blood by facilitating an in situ plasma separation, capillary flow and colorimetric reaction occurring concomitantly, without incurring additional device complexity or embodiment. The test reagents were dispensed in lyophilized form, and the resulting paper strips were found to be stable over three months stored in a normal freezer, rendering easy adaptability commensurate with the constrained supply chains in extreme resource-poor settings. Quantitative results could be arrived at via a completely-automated mobile-app-based image analytics interface developed using dynamic machine learning, obviating manual interpretation. The tests were demonstrated to be of high efficacy, even when executed by minimally trained frontline personnel having no special skill of drawing precise volume of blood, on deployment at under-resourced community centres having no in-built or accessible healthcare infrastructure. Clinical validation using 220 numbers of human blood samples in a double-blinded manner evidenced sensitivity and specificity of 98.11% and 96.7%, respectively, as compared to the results obtained from a laboratory-benchmarked biochemistry analyser, establishing its efficacy for public health and community disease management in resource-limited settings without any quality compromise of the test outcome.

Landscape of Continuous Glucose Monitoring (CGM) and Integrated CGM: Accuracy Considerations

Continuous glucose monitoring devices have significantly improved in many respects compared with earlier versions. As sensor accuracy improved, U.S. Food and Drug Administration approved a nonadjunctive indication for use that no longer required confirmatory blood glucose monitoring. This article discusses the performance characteristics and regulatory classifications for the current systems that are relevant to informed clinical decision-making.

Evidence From a Long-Term, Systematic Post-Market Surveillance Program: Clinical Performance of a Hematocrit-Insensitive Blood Glucose Test Strip

BACKGROUND

Described is a manufacturer's systematic post-market evaluation of the long-term clinical accuracy of a commercially available blood glucose monitoring (BGM) test strip product.

METHODS

Production batches of test strips were routinely and regularly sampled and evaluated in a clinical setting to assess product accuracy. Evaluations were performed on capillary blood samples from a minimum of 100 subjects with diabetes, by clinical staff according to instructions for use. Readings were compared against capillary blood samples collected at the same time and measured by a standard laboratory reference method. Clinical accuracy was calculated according to EN ISO 15197:2015.

RESULTS

A total of 21 115 paired results were obtained, equating to 209 production batches over the >3-year period since test strip launch. Of the results, 97.6% met the accuracy criterion (range: 97.1-98.1% by year), with 98.1% of values presenting zero risk as defined by the surveillance error grid. At the <5th (21.0-33.8%) and >95th (48.3-59.4%) percentile extremes of hematocrit distribution, 97.9% and 96.4% of values were clinically accurate. The product also demonstrated clinical accuracy across all seven glucose ranges ("bins") as defined by the standard. Under conditions of combined hematocrit and glucose (<80 mg/dL and ≥300 mg/dL) extremes, 97.7% of values were clinically accurate.

CONCLUSIONS

Methodologies and results from a manufacturer's self-imposed clinical accuracy surveillance program of a BGM product is presented. Given the publication of sometimes-conflicting data presented within ad hoc BGM clinical accuracy evaluations, usually of limited size, it is advocated that BGM manufacturers adopt similarly robust and systematic surveillance programs to safeguard patients.

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.

Why the Details of Glucose Meter Evaluations Matters

In an article in the Journal of Diabetes Science and Technology, Macleod and coworkers describe an evaluation of LifeScan glucose meters that focus on the effects of sample types and comparison methods. They make a valid point that these factors influence the accuracy observed in evaluations and recommend the comparison method be the one recommended by the manufacturer for the sample type in the intended use statement. Yet, the recommended comparison method is not a reference method. The accuracy hierarchy of definitive, reference, and field methods originally described by Tietz should remind one that virtually all glucose meter evaluations use commercially available field methods as the comparison method. Finally, one should not neglect the FDA adverse event database as a way to assess glucose meter performance.

Measures of Accuracy for Continuous Glucose Monitoring and Blood Glucose Monitoring Devices

Currently, patients with diabetes may choose between two major types of system for glucose measurement: blood glucose monitoring (BGM) systems measuring glucose within capillary blood and continuous glucose monitoring (CGM) systems measuring glucose within interstitial fluid. Although BGM and CGM systems offer different functionality, both types of system are intended to help users achieve improved glucose control. Another area in which BGM and CGM systems differ is measurement accuracy. In the literature, BGM system accuracy is assessed mainly according to ISO 15197:2013 accuracy requirements, whereas CGM accuracy has hitherto mainly been assessed by MARD, although often results from additional analyses such as bias analysis or error grid analysis are provided. The intention of this review is to provide a comparison of different approaches used to determine the accuracy of BGM and CGM systems and factors that should be considered when using these different measures of accuracy to make comparisons between the analytical performance (ie, accuracy) of BGM and CGM systems. In addition, real-world implications of accuracy and its relevance are discussed.