The application of theoretical goals based on biological variation data in proficiency testing.

Proficiency testing schemes must define acceptable standards of performance. A number of strategies have been used to define acceptable standards, or analytical goals, for imprecision, but it does appear that the current widely held view is that imprecision (as SD or coefficient of variation) should be equal to or less than one half of the average intraindividual biological variation. Since the goal for inaccuracy is that results should be unbiased, the biological variation-based goals should be used for total laboratory error. Many data on the biological variation of a wide range of analytes now exist, which facilitates goal-setting. Current proficiency testing schemes generally analyze laboratory data using either a parametric statistical approach or empirical fixed limits of acceptability. The latter strategy appears to have advantages provided that the criteria of acceptability are the objective biological variation-based goals.