Target Values and Method Evaluation in Proficiency Testing Programs

Abstract

A recent opinion article (1) in this journal presented sound metrologic principles and a plan of action to improve analytical accuracy in medical laboratories. In addition to the use of Certified Reference Materials outlined by Muller (1), use of proficiency testing and external quality-control programs can have a broader impact on interlaboratory comparability. Ideally, target values should be derived from reference methods and reference materials, but both are limited in their availability, and the mean (or other indicator of central tendency) of participant data is frequently used. This has been shown to provide a basis of comparison often comparable to reference methods (2). The means of subsets of methods (peer-group means) are often reported as target values, a practice usually ascribed to method-dependent behavior of proficiency test specimens and so-called matrix effects (3)(4); this use of multiple “true values” in proficiency testing has been criticized (5)(6). In the US, the CLIA’88 serves as the basis for any accredited external quality-control program. The current regulations (7) state …