Properties and units in the clinical laboratory sciences. Part XXVII: online dynamic NPU manual (IUPAC Technical Report)

1.1 Scope

The purpose of this project is to describe the NPU terminology in its core essence by conveying the principles and rules in a systematic approach on an online platform (Online NPU Dynamic Manual) to users of the NPU terminology and generally to the medical laboratory communities. The principles and rules from previous publications in the series on properties and units in the clinical laboratory sciences and Silver Book [21] have been conveyed on the online platform. New rules or alterations in current rules described in future publications will be updated (dynamic) on the platform. One draft containing the principles and rules was established, followed by frequent meetings in which the rules, how to communicate the information, and which information structure should be on the platform were discussed. The goal of the online platform is to first establish all kinds-of-property and in the future continue to build the platform with interlinks.

1.2 Outcome

The general principle of this work is to provide descriptions of the NPU terminology that are systematic, up to date, and understandable from aforementioned and future publications. The authors have attempted to describe key concepts and definitions that have been described in previous publications, with examples that will be succinct and comprehensible for medical laboratorians while still remaining true to pure metrological principles from reference publications such as the Vocabulary of International Metrology [33] and Silver Book [21]. Thus, the pages are generally structured with definitions, references, examples, further descriptions/explanations, historical changes/documentations, and discussions. Several concepts are interlinked to individual pages that are either elaborating the issues relating to the concepts or elaborating the concepts in the Vocabulary section. Simple search tools on the frontpage and the dedicated sections were established, enabling a search for specific issues or concepts in the entire homepage or in a specific section.

The dynamic NPU terminology manual was established on a homepage, https://labterminology.com/. From the starting page (Fig. 1), the readers may enter three main sections: NPU concept model, List of kinds-of-property, and Vocabulary (Figs. 2–4). A link to the homepage’s forum is also provided.

Fig. 1:

This is the entrance of the homepage that is divided into 5 parts from top to bottom. First upper part shows the logo of the project and leading links to the main sections. Second upper part is a search tool. Middle section is giving an introducing text to the homepage, a banner demonstrating which subsections have been updated, and leading links to the main sections, except “forum”. Bottom shows contact information and the main structure of the homepage.

Fig. 2:

The section shows the entrance to the NPU concept model with links to the subparts of the NPU terminology. The principle of each subpart is described with formal definitions and examples.

Fig. 3:

The section shows the list of kinds-of-property that are or have been used in NPU codes. Each kind-of-property is described with formal definitions and examples.

Fig. 4:

Vocabulary section is a growing section that will strive to contain relevant concepts used in the NPU terminology.

1.3 NPU concept model

This section describes the principles and rules of the NPU terminology and general recommendations on properties and measurement units (Fig. 2). To understand the principles of the terminology, each subject will be presented by principles, rules, examples, and detailed explanations. For example, a variety of measurement units for the same quantity have been reported, e.g., hemoglobin in blood in g/dL, mg/dL, and g/L [34], [35], [36]. This practice of having measurement units with an SI prefix in the denominator, as shown by the first two units in the above examples, has been discouraged by the initiators of NPU terminology and supported later by the joint committee of Committee of NPU terminology (C-NPU) from International Federation of Clinical Chemistry and Laboratory Medicine and subcommittee on NPU (SC-NPU) from International Union of Pure and Applied Chemistry (abbreviated SC-C-NPU) [37]. The vast variation of measurement units may cause errors of communication which can potentially lead to patient mistreatment [21, 25, 37]. To specify and clarify these types of principles to the medical scientific communities, each subsection of NPU concept model section will be able to present the reasons for standardization in communication of laboratory results which are essential for in-patient care.

1.4 List of kinds-of-property

A list of kinds-of-property was established with 137 posts with examples and explanations in order to understand which rules and principles apply for each kind-of-property and how it is used in the terminology. The kinds-of-property are classified into three categories according to Dr. Dybkær’s publication [26]. Each kind-of-property is presented by definitions (in words and mathematical equations when relevant), references, examples, concept relationship, historical changes/documentations, and detailed descriptions/explanations. To illustrate the practical use, the examples, when possible and relevant, are presented for every medical laboratory field (e.g., clinical biochemistry, allergy, microbiology, immunology, genetics), if possible.

1.5 Vocabulary

Basic metrology and laboratory concepts from International Vocabulary of Metrology (VIM) [33] and Silver Book [21] used in the terminology are presented in a medical laboratory context in this section with definitions and examples.

1.6 Governance and maintenance of the dynamic NPU manual

The joint committee of NPU terminology (SC-C-NPU) has the responsibility for the structure and content. The homepage will continuously be updated after formal decisions either from SC-C-NPU meetings or from NPU-related publications that are reviewed, accepted, and approved by SC-C-NPU. Consequently, noticeable changes will be documented and elaborated in these official documents that are traceable. Furthermore, profound descriptions of background, pro and con arguments, consequences, and decision of new or altered principles/rules should be provided in the official documents, enabling an understandable insight to current and future users. The documents will serve as references at the homepage. Clarifications of principles or rules may be inserted on the homepage, without official notification, after approval by SC-C-NPU.

2.1 Future developments

The homepage content and general usability will continue to be developed and reviewed by users, NPU experts, and administrators from NPU release centers and therefore should provide a flexible and up-to-date summary of the terminology and any future decisions to modify and improve it. Online access will allow access from any online device, ensuring portability and hopefully improving the value as an easily accessible resource. Relevant changes in the manual will be performed accordingly and continuously.

In summary, the online dynamic manual will strive to provide an education and reference resource for users of the NPU terminology and those that seek to continually improve it. The dynamic manual is linked from web place for C-NPU and SC-NPU, https://www.npu-terminology.org/, and is currently also accessible at https://labterminology.com/.

2.2 Membership of sponsoring bodies

Membership of the IFCC Scientific Division during the period 2017–2021 was as follows:

Chair: Philippe Gillery (France); Vice-Chair: Christa M. Cobbaert (Netherlands); Secretary: Joseph Passarelli (United States) and Garry John (United Kingdom) from 2021; Members and Consultants: Konstantinos Makris (Greece), Mario Plebani (Italy), Karen W. Phinney (NIST Consultant, United States), Michael Rottmann (Germany), Ian Young (ICHCLR Observer, United Kingdom), Karen Phinney (NIST Consultant, United States), Yang Zhen (NIFDC Observer, China), Chris Burns (NIBSC Consultant, United Kingdom), Greg Miller (JCTLM Consultant, United States), Barnali Das (India), Liesbet Drepez (JRC Observer, Belgium), and Ralf Josephs (BIPM Observer, France).

Membership of the IUPAC Chemistry and Human Health Division Committee during the period 2017–2021 was as follows:

President: Rita Cornelis (Belgium); Vice President: Helle Møller Johannessen (Denmark); Secretary: Michael Schwenk (Germany); Titular Members: Vincenzo Abbate (United Kingdom), Edmond Differding (Belgium), A. Ganesan (United Kingdom), Vladimir Gubala (United Kingdom), Linda Johnston (Canada), and Helle Møller Johannessen (Denmark).

Membership of the IFCC Committee on Nomenclature for Properties and Units during the preparation of this report (2017–2021) was as follows:

Chair: Karin Toska (Norway), Young Bae Lee Hansen (Denmark) from 2021; Members: Sridevi Devaraj (United States), Fatma Meric Yilmaz (Turkey), Koh Furuta (Japan), and Eline van der Hagen (Netherlands).

Membership of the IUPAC Subcommittee on Nomenclature for Properties and Units during the preparation of this report (2017–2021) was as follows:

Chair: Helle Møller Johannessen (Denmark); Members: Ivan Bruunshuus (Denmark), Robert Flatman (Australia), Daniel Karlsson (Sweden), Gunnar Nordin (Sweden), Karin Toska (Norway), Young Bae Lee Hansen (Denmark). Ulla Magdal Petersen (Denmark), and Rebecca Ceder, (Sweden).