Measurement Uncertainty in the Hemostasis Laboratory

Abstract: Clinical laboratory results are inherently uncertain. Variability arises when repeating measurements of the same sample under different conditions. Measurement uncertainty (MU) is a metrological framework that quantifies this variability, enabling clinical interpretation and comparison of results within and between patients. In hemostasis assays, MU describes uncertainty propagation across the entire traceability chain-from international standards to final patient results. Abstract: The Guide to the Expression of Uncertainty of Measurement (GUM) offered a statistically rigorous but complex method for estimating MU, limiting its widespread adoption. A relatively recent technical specification (TS) from the International Standardization Organization (ISO; ISO/TS 20914:2019) introduced a top-down approach that balances rigor with operational feasibility, supporting ISO 15189 compliance. However, its applicability to specialist areas such as hemostasis has been questioned. Furthermore, despite improved understanding of calculation methods, international guidance recommends against reporting results, together with MU, directly to service users; instead, the laboratory is required to provide it upon request. This review explores the implementation of different approaches for MU in hemostasis laboratories.