Poster

B-116. Does the Eurachem/CITAC Uncertainty of Qualitative Results Guide Comply with ISO Standards?

Authors:
  • Società Italiana di Patologia Clinica e Medicina di Laboratorio (SIPMeL)
Poster

B-116. Does the Eurachem/CITAC Uncertainty of Qualitative Results Guide Comply with ISO Standards?

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Abstract

Background: The Eurachem/CITAC Guide Assessment of Qualitative Analysis [1] is an innovative document, very useful for laboratories. False qualitative analysis results are extremely relevant, e.g., in forensics or doping analysis and in medical examinations. We see at least two critical issues in the EURACHEM document: lack of the precision component and ambiguity between qualitative results and intermediate steps with quantitative measures. Methods: We compared EURACHEM statements with ISO 3534-2 [2], VIM [3], ISO Guide 99 [4], ISO 17025 [5], ISO 15189 [6], ISO 20914 [7], and ISO 16393 [8] requirements. In VIM, measurement uncertainty includes a statistical analysis of values obtained under conditions such as repeatability, intermediate precision, and reproducibility. ISO 17025 requires laboratories to identify contributions to measurement uncertainty, and does not exclude qualitative results, but includes contingencies that preclude rigorous statistical evaluation. ISO 15189 and ISO 20914 require uncertainty in the intermediate measurement steps of qualitative results. ISO 16393 describes the precision of qualitative results. Results: There is no feature in EURACHEM Guide resulting from replicates of measurements, repeatability, inter­mediate precision, and reproducibility. All the characteristics in Table 2 of the Guide (True positive rate, and so on) derive from the comparison of results with a reference external to the laboratory method. Examples 7.3, 7.4, 7.5 and 7.6 in EURACHEM document show qualitative results derived from quantitative measurements. Conclusion: Eurachem/CITAC Guide is an important tool to apply ISO 17025 statement that, when evaluating measurement uncertainty, all contributions which are of significance, including those arising from sampling, shall be taken into account. ISO 17025 does not distinguish between quantitative and qualiative results. ISO 15189 and ISO 20914 do it, but are both under revision. The characteristics of precision, repeatability and reproducibility of methods are useful in the laboratory for the verification and quality control of examination methods. EURACHEM Guide does not resolve the case of qualitative results derived from quantitative measurement. References:[1] R Bettencourt da Silva and S L R Ellison (eds.) Eurachem/CITAC Guide: Assessment of performance and uncertainty in qualitative chemical analysis. First Edition, Eurachem (2021). ISBN 978-0-948926-39-6. Available from https://www.eurachem.org[2] ISO 3534-2:2006 Statistics — Vocabulary and symbols — Part 2: Applied statistics [3] International vocabulary of metrology - Basic and general concepts and associated terms (VIM) 3rd edition 2008. https://www.bipm.org/en/publications/guides [4] ISO/IEC Guide 99:2007. International vocabulary of metrology — Basic and general concepts and associated terms (VIM) [5] ISO/IEC 17025:2017. General requirements for the competence of testing and calibration laboratories [6] ISO/DIS 15189:2021. Medical laboratories — Requirements for quality and competence [7] ISO/TS 20914:2019. Medical laboratories — Practical guidance for the estimation of measurement uncertainty [8] ISO/TS 16393:2019. Molecular biomarker analysis — Determination of the performance characteristics of qualitative measurement methods and validation of methods --- https://www.abstractsonline.com/pp8/#!/10594/presentation/559

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