Original scientific paper

https://doi.org/10.11613/BM.2020.020101

The top-down approach to measurement uncertainty: which formula should we use in laboratory medicine?

Flávia Martinello ; Department of Clinical Analysis, Federal University of Santa Catarina, Florianopolis, Brazil
Nada Snoj ; Institute of Clinical Chemistry and Biochemistry, University Medical Centre Ljubljana, Ljubljana, Slovenia
Milan Skitek ; Institute of Clinical Chemistry and Biochemistry, University Medical Centre Ljubljana, Ljubljana, Slovenia
Aleš Jerin ; Institute of Clinical Chemistry and Biochemistry, University Medical Centre Ljubljana, Ljubljana, Slovenia

Abstract

Introduction: By quantifying the measurement uncertainty (MU), both the laboratory and the physician can have an objective estimate of the
results’ quality. There is significant flexibility on how to determine the MU in laboratory medicine and different approaches have been proposed
by Nordtest, Eurolab and Cofrac to obtain the data and apply them in formulas. The purpose of this study is to compare three different top-down approaches for the estimation of the MU and to suggest which of these approaches could be the most suitable choice for routine use in clinical laboratories.
Materials and methods: Imprecision and bias of the methods were considered as components of the MU. The bias was obtained from certified reference calibrators (CRC), proficiency tests (PT), and inter-laboratory internal quality control scheme (IQCS) programs. The bias uncertainty, the combined and the expanded uncertainty were estimated using the Nordtest, Eurolab and Cofrac approaches.
Results: Using different approaches, the expanded uncertainty estimates ranged from 18.9-40.4%, 18.2-22.8%, 9.3-20.9%, and 7.1-18.6% for cancer antigen (CA) 19-9, testosterone, alkaline phosphatase (ALP), and creatinine, respectively. Permissible values for MU and total error ranged from 16.0-46.1%, 13.1-21.6%, 10.7-26.2%, and 7.5-17.3%, respectively.
Conclusion: The bias was highest using PT, followed by CRC and IQCS data, which were similar. The Cofrac approach showed the highest uncertainties, followed by Eurolab and Nordtest. However, the Eurolab approach requires additional measurements to obtain uncertainty data. In summary, the Nordtest approach using IQCS data was therefore found to be the most practical formula.

Keywords

measurement uncertainty; bias; uncertainty; total error; quality control

Hrčak ID:

238900

URI

https://hrcak.srce.hr/238900

Publication date:

15.6.2020.

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