All types of measurement have some inaccuracy due to bias and imprecision; therefore measurement results can only be estimates of the values of the quantities being measured. To properly use such results, medical laboratories and their clinical users need some knowledge of the accuracy of such estimates.

The complete result of a measurement is a value, a unit and an estimate of uncertainty. This estimate of uncertainty is conventionally referred to as Measurement Uncertainty (MU) and incorporates the cumulative range of factors involved in the testing procedure itself in addition to consideration of the inter-individual and intra-individual biological variation which will potentially influence the overall test result. Evaluating measurement uncertainty is an ISO 15189:2012 accreditation requirement.

In terms of MU determined by the AIA /HSL group of laboratories, it should be noted all assays are performed in strict accordance with the manufacturers’ instructions. MU, which has been estimated for each assay during the verification procedure, is reviewed at regular intervals to ensure that MU values do not exceed the pre-defined maximum allowable uncertainty for each assay.