Measurement Uncertainty

Medical laboratories are responsible for ensuring that test results are fit for clinical application by defining analytical performance goals, selecting and qualifying appropriate measurement procedures. 

All measurement results have some inaccuracies due to analytical bias and imprecision; therefore a measurement result is an estimate at the time of undertaking such measurements. To properly use such results, medical laboratories and their clinical users need some knowledge of the accuracy of such estimates and the uncertainty it may have on the interpretation of patient results.

This estimate of such uncertainties is referred to as Measurement Uncertainty (MU) which incorporates the cumulative range of factors involved in the examination procedure, which may potentially influence the overall test result and thus the interpretation of patient results.

The complete result of a measurement is a value, a unit and an estimate of uncertainty. Medical laboratories consider the impact of such uncertainties on the interpretation of patient results and ensure uncertainties are minimised through control measures such as standardised procedures, Internal Quality Control monitoring and trending and routine evaluation of MU. Evaluating measurement uncertainty is an ISO 15189:2022 accreditation requirement.

It should be noted that all assays within the TDL/HSL group of laboratories use standard operating procedures followed by trained and competency assessed scientists.

The MU is initially estimated for each assay during the qualification of the selected examination procedure and is evaluated against the pre-defined maximum allowable measurement uncertainty. Each MU is then re-estimated at regular intervals with additional data and reviewed against the pre-defined maximum allowable measurement uncertainty to ensure uncertainty values and therefore errors and inaccuracies are minimised. 

Overall assay performance is also regularly monitored through internal quality control (IQC) and external quality assessment (EQA) schemes and incorporated in test result interpretation. MU for individual assays is available upon request.