About traceability of the biochemical measurement results – some case studies on the metrological and practical aspects

The comparability of biochemical measurement results performed by any medical laboratories could be reached only when common reference systems can be established for worldwide use. There is recognised a critical step in the reference systems to achieve traceability of values obtained using reference measurement procedures and reference materials traceable to the universally recognized and accepted reference point such as SI units. The IVD Directive requires traceability of the values assigned to calibrators and/or control materials. It must be assured through available reference measurement procedure and/or available reference materials of a higher order. In this respect, the JCTLM promote and give guidance on internationally recognized and accepted equivalence of measurements in laboratory medicine and traceability to appropriate measurement standards. There are already established higher order metrological reference materials, reference measurement procedures as well as reference measurement services for some biochemical analytes. In laboratories medicine, the metrological traceability and the related metrological concept measurement uncertainty are not always possible to be established. In this paper some traceability case studies for biochemical constituents are presented in opposite with some case studies for hematology measurements performed in medical laboratories. 1. Starting from some definitions As well known there are international activities at the high metrology level regarding the traceability in laboratories medicine. The main goal of obtaining comparability of medical laboratory results over time and space, either by the same measurement procedure or by different measurement procedures, could be reached only when common reference systems can be established for worldwide use. An important step in this process is to achieve the traceability of measured values using the reference measurement procedures and the reference materials to a universally recognized and accepted reference point such as the International System of Units (SI). As a consequence of these needs, the Joint Committee on Traceability in Laboratory Medicine (JCTLM) of International Bureau of Weights and Measures (BIPM) was created to promote and give guidance on internationally recognized and accepted equivalence of measurements in laboratory medicine and traceability to appropriate measurement standards [1]. Nowadays, the traceability issue for medical devices is endorsed by the European Directive 98/79/EC: In vitro diagnostic medical devices (IVD) [2] and by ISO 17511/2000: In vitro diagnostic medical devices Measurement of quantities in biological samples Metrological traceability of values assigned to calibrators and control materials [3]. The directive states as the essential requirement that ”The traceability of values assigned to calibrators and/or control materials must be assured through available reference measurement procedures and/or available reference materials of a higher order.” (IVD 98/79/EC, Annex I, Part A-Clause 3). The traceability is an essential requirement looking especially on the comparability of measurement data due to the impact of the non-traceable IVD measurement systems on the incorrect patient diagnosis and treatment, the impact that can not be easily estimated in the interpretation of clinical studies regarding the health care and patients health in such a way to not compromise the health and safety of patients, users and other third parties. Currently, there are already established higher order metrological reference materials, reference measurement procedures as well as reference measurement services in the medicine laboratories. For practical reasons, it is important to notice from the above definition that the directive refers to the „available” reference materials and reference measurement procedures when dealing with DOI: 10.1051/ C © Owned by the authors, published by EDP Sciences, 2013 201 / 05007 (2013) 305007 16 th metrology International Congress of Metrology, This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2 0 , which . permits unrestricted use, distributi and reproduction in any medium, provided the original work is properly cited. on, Article available at http://cfmetrologie.edpsciences.org or http://dx.doi.org/10.1051/metrology/201305007