Uncertainties in measurement of uncertainty measurements: A commentary from the perspective of a specialist haemostasis laboratory

Determination of uncertainty of measurement (MU) for quantitative testing in clinical pathology laboratories is an accreditation requirement of the National Association of Testing Authorities (NATA). Knowledge of an assay's MU carries various potential benefits for both the laboratory and the organisation. For the laboratory, these include a better understanding of assay limitations and improved comparison of results across laboratories (both local and international). There are currently a number of guidelines and publications available that aim to assist laboratories to establish MU for their quantitative assays. Despite these publications, or perhaps in part because of the existence of multiple publications, derivation of MU is not straightforward. Part of the problem relates to some potentially contradictory information among the publications. In addition, there have been questions raised regarding whether some of the guidelines may underestimate MU, or otherwise not fully comply with NATA (or ISO) requirements. Furthermore, there are specific test situations where some of the suggested approaches may not work as well as others, but this may not be recognised by some laboratories. The current commentary highlights some of the limitations and seemingly conflicting approaches recommended by various publications, from the perspective of a specialist haemostasis laboratory. Nevertheless, many of the examples depicted in this report will hold true for many other laboratory tests and pathology laboratories.