How Should Blood Glucose Meter System Analytical Performance Be Assessed?

Abstract

Blood glucose meter system analytical performance is assessed by comparing pairs of meter system and reference instrument blood glucose measurements measured over time and across a broad array of glucose values. Consequently, no single, complete, and ideal parameter can fully describe the difference between meter system and reference results. Instead, a number of assessment tools, both graphical (eg, regression plots, modified Bland-Altman plots, and error grid analysis) and tabular (eg, International Organization for Standardization guidelines, mean absolute difference, and mean absolute relative difference) have been developed to evaluate meter system performance. The strengths and weaknesses of these methods of presenting meter system performance data, including a new method known as Radar Plots, are described here.

Keywords: accuracy; blood glucose monitoring system; performance; precision.

Figure 1.

Graphical representation of the concepts of precision and trueness. A circular target is used to illustrate precision (the degree of dispersion of deviations from the center of the target) and trueness (the average deviation from the center of the target).

Figure 2.

Visualization of BGMS accuracy using regression plots. For each panel, the black diagonal line represents the ideal scenario (y = x); ISO criteria are plotted using dashed lines; the red line denotes the regression line; and the regression equation and R² value are shown in the top left corner of the plot area. BGMS, blood glucose monitoring system; ISO, International Organization for Standardization; YSI, YSI glucose analyzer.

Figure 3.

BGMS accuracy visualized using modified Bland–Altman plots. For each panel, the black diagonal line represents the ideal scenario (y = 0) and ISO criteria are plotted using dashed lines. BGMS, blood glucose monitoring system; ISO, International Organization for Standardization; YSI, YSI glucose analyzer.

Figure 4.

Surveillance error grid analysis to evaluate the clinical risk associated with BGMS inaccuracy. As shown in the legend, the level of clinical risk associated with each pair of BGMS and reference results is represented by a color on the grid. BGMS, blood glucose monitoring system; YSI, YSI glucose analyzer.

Figure 5.

Visualization of BGMS accuracy using Radar Plots. Each data point represents the error of a meter system result; error is given in units of mg/dL for YSI results <100 mg/dL (region of the plot within the magenta dashed lines) and in units of percentage for YSI results ≥100 mg/dL (region of the plot outside the magenta dashed lines). The outer green circle (bolder line) represents ISO 15197:2013 accuracy criteria; data points within this circle (the 15-15 Zone) meet these criteria. In a Radar Plot, the distance from the center of the plot to a data point indicates the magnitude of the meter system error. The direction of a line connecting the point to the center indicates the value of the laboratory reference measurement. If the point is above the horizontal midline, the error is positive (ie, the meter system overestimated the laboratory reference blood glucose value). If the point is below the horizontal midline, the error is negative (ie, the meter system underestimated the laboratory reference blood glucose value). If the laboratory reference blood glucose value is <100 mg/dL (~5.55 mmol/L), then the errors are expressed in mg/dL (or mmol/L). Otherwise, the errors are expressed as a percentage of the laboratory reference measurement. BGMS, blood glucose monitoring system; YSI, YSI glucose analyzer.