Harmonisation of Measurement Procedures: how do we get it done?

Clinical laboratory measurement results must be comparable among different measurement procedures, different locations and different times in order to be used appropriately for identifying and managing disease conditions. Harmonisation in the broad sense is the overall process of achieving comparability of results among clinical laboratory measurement procedures that measure the same measurand. The term standardisation is used when comparable results among measurement procedures are based on calibration traceability to SI using a reference measurement procedure of the highest available order. When there is no higher order reference measurement procedure available, and it is unlikely that one can be developed, the term harmonisation refers to any process for achieving comparable results among measurement procedures for an individual measurand.This review explains calibration traceability and focuses on the principles of harmonisation for those measurands for which a reference measurement procedure does not exist. We discuss the value of harmonisation, the importance of commutable reference materials, the barriers to harmonisation that exist today, and conclude with a discussion of a current global effort to improve the state of harmonisation.