René Dybkaer

Metrological traceability of measurement results in chemistry: Concepts and implementation (IUPAC Technical Report)

This IUPAC study aims at formulating recommendations concerning the metrological traceability of a measurement result in chemistry. It is intended to provide the chemical measurement community with a consistent view of the creation, meaning, and role of metrological traceability and its underpinning concepts. No distinction is made between measurement results obtained in “high metrology” and in the “field”. A description is given of the calibration hierarchies needed in different circumstances to arrive at metrological traceability along a metrological traceability chain. Flow charts of generic calibration hierarchies are presented as well as a variety of examples. The establishment, assessment, and reporting of metrological traceability are discussed, including the provision of metrological references by a metrological institutional framework and the role of interlaboratory comparisons.

Unit "katal" for catalytic activity (IUPAC Technical Report)

Expressing the amount of a catalyst is often most conveniently done by assessing its catalytic effect. Under zero-order kinetics the catalyzed rate of conversion for a specified reaction is constant and proportionate to the amount-of-substance concentration of catalyst present. Defining the kind-of-quantity “catalytic activity” as a property of the catalyst measured by the catalyzed rate of conversion, the coherent SI unit is mole per second. Following thorough discussions in the IUPAC, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), the International Union of Biochemistry and Molecular Biology (IUBMB), and the World Health Organization (WHO), a petition was presented by the IFCC to the International Committee for Weights and Measures (CIPM) on a special name “katal”, symbol kat, for “mole per second” when used in measuring catalytic activity. This request was granted by the General Conference for Weights and Measures (CGPM) by Resolution 12 (1999). Hereafter, the coherent SI unit katal = 1 mol ⋅ s–1 should replace the off-system IUB unit “(enzyme) unit” = 1 μmol ⋅ min–1 ≈ 16.67 nkat. Thus, by suitable definition of reaction conditions, results for catalytic activity and derivative kinds-of-quantity are metrologically traceable to the SI.

An outline for a vocabulary of nominal properties and examinations - basic and general concepts and associated terms

Abstract Scientists of disciplines in clinical laboratory sciences have long recognized the need for a common language for efficient and safe request of investigations, reporting of results, and communication of experience and scientific achievements. Widening the scope, most scientific disciplines, not only clinical laboratory sciences, rely to some extent on various nominal examinations, in addition to measurements. The ‘International vocabulary of metrology – Basic and general concepts and associated terms’ (VIM) is designed for metrology, science of measurement. The aim of the proposed vocabulary is to suggest definitions and explanations of concepts and terms related to nominal properties, i.e., properties that can be compared for identity with other properties of the same kind-of-property, but that have no magnitude. Clin Chem Lab Med 2010;48:1553–66.

From total allowable error via metrological traceability to uncertainty of measurement of the unbiased result

The concept of “total allowable error”, investigated by Westgard and co-workers over a quarter of a century for use in laboratory medicine, comprises bias as well as random elements. Yet, to minimize diagnostic misclassifications, it is necessary to have spatio-temporal comparability of results. This requires trueness obtained through metrological traceability based on a calibration hierarchy. Hereby, the result is associated with a final uncertainty of measurement purged of known biases of procedure and laboratory. The sources of bias are discussed and the importance of commutability of calibrators and analytical specificity of the measurement procedure is stressed. The practicability of traceability to various levels and the advantages of the GUM approach for estimating uncertainty are shown.

Evolution of Philosophy and Description of Measurement (Preliminary Rationale for VIM3)

Abstract: Different approaches to the philosophy and description of measurement have evolved over time, and they are still evolving. There is not always a clear demarcation between approaches, but rather a blending of concepts and terminologies from one approach to another. This sometimes causes confusion when trying to ascertain the objective of measurement in the different approaches, since the same term may be used to describe different concepts in the different approaches. Important examples include the terms “value,” “true value,” “error,” “probability” and “uncertainty.” Constructing a single vocabulary of metrology that is able to unambiguously encompass and harmonize all of the approaches is therefore difficult, if not impossible. This paper examines the evolution of common philosophies and ways of describing measurement. Some of the differences between these approaches are highlighted, which provides a rationale for the entries and structure of the August 2006 draft of the 3rd Edition of the International Vocabulary of Metrology – Basic and General Concepts and Associated Terms (VIM3).

Properties and units in the clinical laboratory sciences. Part XXIII. The NPU terminology, principles, and implementation: A user’s guide (IUPAC Technical Report)

This document describes the application of the syntax, semantic rules, and format of the Nomenclature for Properties and Units (NPU) terminology for coded dedicated kinds-of-property in the various subject fields of the clinical laboratory sciences. The document sums up considerations and reasoning by the Committee and Subcommittee on Nomenclature for Properties and Units (C-SC-NPU) and collects the experience with the system through some eight years of application in electronic health communication. Access to the NPU terminology in English is currently at <www.labterm.dk>, via the English download files from the Danish Release Centre under the National Board of Health. Updates to the terminology are usually presented once a month.

Clinical laboratory sciences data transmission : the NPU coding system

In health care services, technology requires that correct information be duly available to professionals, citizens and authorities, worldwide. Thus, clinical laboratory sciences require standardized electronic exchanges for results of laboratory examinations. The NPU (Nomenclature, Properties and Units) coding system provides a terminology for identification of result values (property values). It is structured according to BIPM, ISO, IUPAC and IFCC recommendations. It uses standard terms for established concepts and structured definitions describing: which part of the universe is examined, which component of relevance in that part, which kind-of-property is relevant. Unit and specifications can be added where relevant [System(spec)-Component(spec); kind-of-property(spec) = ? unit]. The English version of this terminology is freely accessible at http://dior.imt.liu.se/cnpu/ and http://www.labterm.dk, directly or through the IFCC and IUPAC websites. It has been nationally used for more than 10 years in Denmark and Sweden and has been translated into 6 other languages. The NPU coding system provides a terminology for dedicated kinds-of-property following the international recommendations. It fits well in the health network and is freely accessible. Clinical laboratory professionals worldwide will find many advantages in using the NPU coding system, notably with regards to an accreditation process.

Properties and units in the clinical laboratory sciences, Part XXIII. The NPU terminology, principles and implementation -a user's guide (Technical Report 2011) (IFCC-IUPAC).

Abstract This document describes the application of the syntax, semantic rules and format of the NPU terminology for coded dedicated kinds-of-property in the various subject fields of the clinical laboratory sciences. The document sums up considerations and reasoning by the C-SC-NPU and collects the experience with the system through some 8 years of application in electronic health communication. Access to the NPU terminology in English is currently at www.labterm.dk, via the English download files from the Danish Release Centre under the National Board of Health. Updates to the terminology are usually presented once a month.

Properties and units in the clinical laboratory sciences Part XX. Properties and units in clinical and environmental human toxicology (IUPAC Technical Report)

This document describes the introduction of the concept of property in the field of clinical and environmental human toxicology for the presentation of results of clinical laboratory investigations. It follows the IFCC-IUPAC systematic terminological rules and attempts to create a common base for communication between the clinical chemist, the medical practitioner, the human toxicologist, and the environmental toxicologist. The term designating a substance being a toxicant may be an international nonproprietary name (INN), a generic name, a registered trade name, a fantasy name, or other. This causes difficulties in the transmission of requests and reports on properties involving substances in biological fluids and environmental media to and from laboratories, to the end user, and in the collating of this information from different sources. The document comprises a list of properties of human and environmental systems involving toxicants for use in transmitting medical laboratory data. The document recommends terms based on the format developed by the IFCC and IUPAC to facilitate interaction between disciplines and unambiguous interpretation of data, e.g., for purposes of risk interpretation. Systematic terms are presented together with a code (identified by the letters NPU) for each. The complete CNPU Database may be found at http://dior.imt.liu.se/cnpu/info.htm.

Metrology in laboratory medicine – Reference measurement systems

Abstract The medical laboratory must provide results of measurements that are comparable over space and time in order to aid medical diagnosis and therapy. Thus, metrological traceability, preferably to the SI, is necessary. The task is formidable due to the many disciplines involved, the high production rate, short request-to-report time, small sample volumes, microheterogeneity of many analytes, and complex matrices. The prerequisite reference measurement systems include definition of measurand, unit of measurement (when applicable), consecutive levels of measurement procedures and calibrators in a calibration hierarchy, international organizations, reference measurement laboratories, dedicated manufacturers, written standards and guides for the medical laboratory, production of reference materials, internal and external quality control schemes, and increasingly accreditation. The present availability of reference measurement procedures and primary calibrators is shown to be insufficient to obtain international comparability of all types of quantity in laboratory medicine.