All quantitative measurements have inherent variation. Laboratories accredited to ISO 15189 must assess the level of uncertainty of their test results. The standard states “The laboratory shall determine the uncertainty of results, where relevant and possible. Uncertainty components which are of importance shall be taken into account.”. Guidance to the application of uncertainty of measurement (MU) is available from NRL.
The NRL has developed a system for estimating and reporting MU for quantitative assays based on a comparison of your laboratory’s QC results with those reported by other laboratories using the same QC sample/assay combination (peer group).
The methodology for comparing MU is published and scientifically validated. The MU estimation accounts for the assay’s imprecision (random error) and bias (systematic error). The imprecision is measured by calculating the standard deviation (SD) of the QC sample results over a defined period of time. The bias, expressed as a SD, is calculated by comparing the mean of the QC sample results with a weighted mean of all the QC sample results of the peer group. The imprecision and bias are combined to obtain a combined standard uncertainty. This is multiplied by a factor of 2 to obtain an expanded uncertainty, which is the 95% confidence interval of the measurement.
MU Reports are compulsory, for quantitative assays, in some countries and jurisdictions globally. Laboratories accredited to ISO 15189 must assess their level of uncertainty of their test results.
Scientifically validated MU reporting is now automated and available within EDCNet for on demand download for subscribed members.
Utilising global peer group data for the same test analytes, MU report estimation is available in report format and covers imprecision (random error) and bias (systematic error).