B-155 Easiness of Uncertainty Estimation and Use for Quantitative and Qualitative Results According to ISO

  • Società Italiana di Patologia Clinica e Medicina di Laboratorio (SIPMeL)
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The revision of ISO 15189 retains the requirement for uncertainty estimation, referring to ISO/TS 20914 for implementation. [1] With document Q16 [2], SIPMeL collects the main ISO, literature, and CLSI guidance on the topic. Typical examples of application of the Q16 Recommendations are presented here to demonstrate their ease of use. Methods: The performance characteristics of an assay with quantitative results ( ALT EC are derived from refs [3] and [4]. A test with "qualitative" results, Abbott BinaxNOW-19 COVID-19 Ag card [5] [6], is then described. The SIPMeL Q16 recommendations provide for quantitative results, and for quantitative phases of examinations with nominal results, the calculation of type deviation (σ) from the long-term IQC data and the repeatability limit from type deviation (σ) in the series. For nominal qualitative results, and for the weakly positive result of a method that provides ordinal qualitative values, the CQI for a material near the detection limit or C95 provides a frequency value of positives (POD%), while the repeatability check uses the equality criterion between two repeated results. Results: The uncertainty component of the calibration, the prerogative of the manufacturers, is set to zero. The precision component results for ALT σ 2.94 U/L (CV 8.3%), extended uncertainty (U) 5.88 U/L (16.6%), while for COVID-19 Ag the precision of the chosen level is fixed at POD 95%. Results of duplicate testing are presented. Conclusion: In the medical laboratory, pressured by the amount of tests to be performed and turnaround times to be met, procedures for quality must be easily executable, simple, intuitively understandable, robust, and uncontroversial. This is what ISO 20914 and a long list of ISO and CLSI documents, collected in SIPMeL Q16, are for. Knowledge of uncertainty provides the laboratory with awareness of the reliability of results, information that is shared with users or third parties, for example, in accreditation inspections. "Precision" requires repetitions of the measurement on the same material at a set level. For qualitative results, it is easy to determine how often observations differ from each other, rather than measuring by how much observations differ from the mean. References: 1. Pradella M. Alcune certezze dell'incertezza di misura: nuova ISO 20914 e raccomandazioni SIPMeL. Riv Ital Med Lab 2021 Sep 15. DOI: 10.23736/S1825-859X.21.00112-22. SIPMeL Recommendations for estimating measurement uncertainty in medical laboratories (ISO 15189 and ISO 20914) 3. Biswas SS et al. Evaluation of imprecision, bias and total error of clinical chemistry analysers. Indian J Clin Biochem. 2015 Jan;30(1):104-8. 4. Beckman Coulter. Alanine Aminotransferase (ALT). 5. Perchetti GA et al. Analytical Sensitivity of the Abbott BinaxNOW COVID-19 Ag Card. J Clin Microbiol. 2021 Feb 18;59(3):e02880-20. 6. Abbott. BinaxNOWTM COVID-19 Ag CARD --- ---!/10594/presentation/337

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The estimation of measurement uncertainty is required for accreditation of medical laboratories, according to the International Organization for Standardization (ISO). ISO provides adequate indications to obtain uncertainty and above all precision and repeatability with simplicity in laboratories of any type and size, both for numerical quantitative and nominal qualitative results. Other consistent guidelines are contained in various documents of the Clinical & Laboratory Standards Institute (CLSI). The Recommendations of the Italian Society of Clinical Pathology and Laboratory Medicine (SIPMeL) with document Q16 bring together the sources and provide a clear and simple description of how they should be applied.