Improving the supply of clinical reference materials via collaborative efforts for the coordination of reference measurements. G. O’Connor, Braunschweig, DE Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany and Technische Universität Braunschweig, Braunschweig, Germany National Measurement Institutes (NMIs) currently assure the traceability of their measurement results for a small number of highest priority clinical measurands by conduct comparison studies to demonstrate their equivalence and hence their capabilities for providing traceable measurement results for supporting globally comparable patient measurement results. The procedures used by the NMIs in these comparisons are the same as those used to characterise reference materials and to provide assigned values to proficiency testing schemes. Whilst these procedures provide the best trueness and lowest measurement uncertainty, they are highly labour intensive and time consuming and therefore the number of such studies are limited. To address this issue the Organic Analysis Working Group (OAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) co-ordinates studies that enable NMIs to back broader claims by looking at specific measurands that challenge particular analytical skills and that can be reasonably assumed to represent a wider group of measurands as agreed by the technical experts within the working group. This provides a mechanism for assuring the equivalence of measurement results provided by NMIs when assigning values to certified reference materials (CRMs). The number of measurands being prioritised by clinical laboratory experts is increase, as to is their complexity and the challenges of dealing with lower concentrations. Therefore, it is not possible for a single NMI to cover the wide range of materials or reference measurement being requested. To address these issues NMIs are starting to coordinate their activities. An example of this is the newly formed European Metrology Network for Traceability in Laboratory Medicine, where NMIs are working together to ensure a broader scope of activities and limited the duplication of effort between NMIs. In order to fully achieve their aims, NMIs must work closely and collaboratively with clinical lab medicine experts, invitro diagnostic providers and legislators to ensure that measurands are appropriately prioritised and that reference measurement procedures and commutable RMs are available to assure the comparability of real patient measurement results.