Pre-metrological (pre-analytical) variation of some biochemical quantities

It is customary to assume that pre-metrological variation is negligible if all pre-metrological sources of variation have been standardised. The aim of this study was to quantify the pre-metrological variation of some biochemical quantities frequently measured in clinical laboratories. The experimental design considers the different sources of pre-metrological variation that usually act day-to-day on samples from patients. The results demonstrate that, for many quantities, the pre-metrological variance is not negligible; consequently, it is suggested that these variances should be taken into account when estimating the uncertainty of measurement of patients' results.