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

Abstract

Background: Anecdotal blood glucose assessments conducted by health care professionals (HCPs) in the field have highlighted differences in results when methodology used is not according to best practices for measuring blood glucose. This study assessed the impact on accuracy of blood glucose measurements when methodology deviates from the recommended study design and recommended reference instrument.

Methods: Adults with type 1 or type 2 diabetes provided capillary and venous blood samples for accuracy assessments using OneTouch® Verio® (Verio) and OneTouch® Ultra 2® (Ultra) blood glucose meters (BGM) and two different reference instruments.

Results: Increases in mean bias were observed when comparing capillary to venous samples tested on the BGMs and the recommended reference instrument. Mean bias was even greater when a hospital blood glucose analyzer was used to measure venous plasma glucose. Increases in mean bias observed for Ultra BGM when testing venous blood on the meter compared to the recommended reference instrument was likely due to the interfering effects of low oxygen levels in the venous blood sample. Conversely, Verio meters, which are insensitive to low oxygen levels, showed little difference from baseline when testing venous blood on the meter compared to results from the same venous sample measured on a reference instrument.

Conclusions: Deviations from the best practice study design of comparing capillary blood glucose results tested on the blood glucose meter with the manufacturer's stated reference instrument will affect accuracy of blood glucose measurements.

Keywords: Ultra; Verio; YSI; blood glucose accuracy; blood glucose monitor.

Figure 1.

Difference plot of capillary result on meter versus capillary result on YSI for lay user performance. (A) Ultra product. Bias was calculated as an absolute bias for all bias results <75 mg/dL and percentage bias for all bias results ⩾75 mg/dL. Of results, 97.7% were within ± 15 mg/dL or 20% of reference. Average bias was 1.1. (B) Verio product. Bias was calculated as an absolute bias for all bias results <100 mg/dL and percentage bias for all bias results ⩾100 mg/dL. Of results, 95.9% were within ± 15 mg/dL or 15% of reference. Average bias was 5.5.

Figure 2.

Mean bias for all comparison groups and meter types. Each point represents the mean bias ± 95% confidence interval of two lots calculated as an absolute mean bias for all bias results <100 mg/dL plus mean percentage bias for all bias results ⩾100 mg/dL. Open symbols represent HCP facilitated testing and closed symbols represent self-testing by the study subjects. Self, subject performs test on the meter; HCP, health care professional performs the test on the meter; Ultra, meter uses OneTouch Ultra test strips; Verio, meter uses OneTouch Verio test strips. Cap-Cap, capillary whole blood as sample source for meter and reference instrument; Cap-Ven, capillary whole blood as sample source for meter and venous blood as sample source for reference instrument; Ven-Ven, venous blood as sample source for meter and reference instrument; YSI, Yellow Springs Instruments 2300; Hosp, Abbott Architect C16000 and Siemens ADVIA 2400. Group nomenclature follows description in Tables 1 and 3.

Figure 3.

Bias of difference between YSI and hospital analyser results for venous blood samples. Bias was calculated as an absolute bias for all bias results <100 mg/dL and percentage bias for all bias results ⩾100 mg/dL. The hospital analyzers used were Siemens ADVIA 2400 at one site and Abbott Architect C16000 at 2 sites.