Background: We developed a two-dimensional plot for viewing trueness that takes into account potential shift and variable quality requirements to verify trueness using certified reference material (CRM).
Methods: Glucose, total cholesterol (TC), and creatinine levels were determined by two kinds of assay in two levels of a CRM. Available quality requirements were collected, codified, and sorted in an ascending order in the plot's header row. Centering on the mean of measured values from CRM, the "mean ± US CLIA '88 allowable total error" was located in the header of the leftmost and rightmost columns. Twenty points were created in intervening columns as potential shifts. Uncertainties were calculated according to regression between certified values and uncertainties of CRM, and positioned in the corresponding columns. Cells were assigned different colors where column and row intersected based on comparison of the 95% confidence interval of the percentage bias with each quality requirement.
Results: A glucose assay failed to meet the highest quality criteria, for which shift of +0.13-0.14 mmol/l was required. A TC assay met the quality requirement and a shift of ±0.03 mmol/l was tolerable. A creatinine assay also met the quality requirement but any shift was not tolerable.
Conclusion: The plot provides a systematic view of the trueness of quantitative laboratory tests.
Keywords: bias; quality requirement; shift; trueness; verification.
© 2014 Wiley Periodicals, Inc.