An improvement on the criterion of the state of the art to estimate the maximal allowable imprecision.

One criterion recommended (1,2) for establishing the maximal allowable imprecision is derived from the biological variability data. According to this criterion, the metrological coefficient of variation must be equal to or less than one-half of the within-subject biological coefficient of variation. When information about biological variability is not available, or when current procedures give better results for imprecision than the goals set with this criterion, the so-called "state of the art" criterion is generally used. According to this criterion, the maximal allowable imprecision for physiological concentrations must be less than the 0.20 fractile of the between-run imprecision (CV) of the laboratories in an external quality assessment scheme.