The standardization journey and the path ahead
Standardization of clinical laboratory test results has progressed through several stages. External quality assessment (EQA) identified that results were not equivalent in different laboratories in the 1950s. Approaches to use the same methods were promoted in the 1960s and the challenges recognized during the 1970s as in vitro diagnostics manufacturers introduced a variety of technologies to meet the demand for clinical laboratory testing services. Hierarchies of national reference systems were developed in the 1980–1990 period that were hampered by inadequate understanding of the importance of commutable reference materials both for use as calibrators and for EQA. Standards for metrological traceability were developed by the International Organization for Standardization in the 2000s that provided a global approach for establishing robust standardization for approximately 100 measurands. The limitations of non-commutable reference materials became widely appreciated in the 2000s. In 2010 and going forward, laboratory medicine recognized the need for harmonization approaches for the large number of measurands for which higher order certified reference materials and reference measurement procedures are not available. Metrological traceability to certified reference materials and reference measurement procedures remains the first choice when technologically feasible. Metrological traceability to an international harmonization protocol provides an alternative when no other approach is realistically feasible. Achieving equivalent results among different medical laboratory measurement procedures remains an important goal to enable appropriate medical decisions based on laboratory results and decision values included in clinical practice guidelines.