Table 2.

Performance Evaluation Toolbox for Handheld POC Devices

Tool	Description
Error grid	Clarke—Clarke grid not useful when data fall 100% within constrained zone “A”
Differences	Mean and median, absolute and relative differences—used in diabetes literature for the evaluation of consumer meter performance by analysis of entire data sets and separate discrete glucose intervals, but lack clinical insight
Statistical	Student's t test for paired differences—robust detection of non-zero mean bias, but positive and negative bias in different ranges can offset each other and mask non-equivalence Repeated-measures analysis of variance—similar masking problems
Regression	Linear least squares—global summary that may not be easily interpretable since it can obscure clinically significant bias and error in particular ranges
Graphical	Bland-Altman plot—provides clinical perspective over measurement range  Mountain plot—shows bias at peak in percentile graph folded at median
ISO standard	ISO 15197—segmental (<75, ≥75 mg/dL) error tolerances for glucose meter results with “bin” populations specified over discrete contiguous intervals of reference measurements
Hybrid	Modified Bland-Altman plot with superimposed ISO 15197 error tolerance bands—visualizes scatter (heteroscedasticity) and reveals erroneous results that fall outside the tolerance bands (proposed FDA licensing requirement)
Post hoc	BPV—based on the Bayesian concept, facilitates identification of Class I and Class II discrepant values (see Materials and Methods)
LS MAD curve	Reveals errors relevant to decision intervals (e.g., TGC, hypoglycemia, and hyperglycemia), employs analyte-specific error tolerance (i.e., LS MAD <5 mg/dL for glucose), visually displays quantitative performance, includes 95% confidence bands, and quickly identifies problem zones with curve “breakouts”