Elsevier

Clinical Biochemistry

Volume 57, July 2018, Pages 29-36
Clinical Biochemistry

Sources and performance criteria of uncertainty of reference measurement procedures

https://doi.org/10.1016/j.clinbiochem.2018.05.018Get rights and content

Highlights

  • Few RMPs report how to estimate the uncertainty of the final measurement.

  • Reference measurement services are available worldwide.

  • Few international EQAS schemes are available for laboratories running the RMPs.

  • Different acceptability criteria are used in the dedicated EQAS schemes.

Abstract

Objective

This article wants to focus on the today available Reference Measurement Procedures (RMPs) for the determination of various analytes in Laboratory Medicine and the possible tools to evaluate their performance in the laboratories who are currently using them.

Methods

A brief review on the RMPs has been performed by investigating the Joint Committee for Traceability in Laboratory Medicine (JCTLM) database. In order to evaluate their performances, we have checked the organization of three international ring trials, i.e. those regularly performed by the IFCC External Quality assessment scheme for Reference Laboratories in Laboratory Medicine (RELA), by the Center for Disease Control and Prevention (CDC) cholesterol network and by the IFCC Network for HbA1c.

Results

Several RMPs are available through the JCTLM database, but the best way to collect information about the RMPs and their uncertainties is to look at the reference measurement service providers (RMS). This part of the database and the background on how to listed in the database is very helpful for the assessment of expanded uncertainty (MU) and performance in general of RMPs. Worldwide, 17 RMS are listed in the database, and for most of the measurands more than one RMS is able to run the relative RMPs, with similar expanded uncertainties. As an example, for a-amylase, 4 SP offer their services with MU between 1.6 and 3.3%. In other cases (such as total cholesterol, the U may span over a broader range, i.e. from 0.02 to 3.6%). With regard to the performance evaluation, the approach is often heterogenous, and it is difficult to compare the performance of laboratories running the same RMP for the same measurand if involved in more than one EQAS.

Conclusions

The reference measurement services have been created to help laboratory professionals and manufacturers to implement the correct metrological traceability, and the JCTLM database is the only correct way to retrieve all the necessary important information to this end.

Introduction

According to the International Vocabulary of Metrology (VIM) a reference measurement procedure (RMP) is defined as “measurement procedure accepted as providing measurement results fit for their intended use in assessing measurement trueness of measured quantity values obtained from other measurement procedures for quantities of the same kind, in calibration, or in characterizing reference materials” [1]. With regard to the measurement procedure, “a detailed description of a measurement according to one or more measurement principles and to a given measurement method, based on a measurement model and including any calculation to obtain a measurement result” is reported. Among the notes, it is written that “a measurement procedure can include a statement concerning a target measurement uncertainty”. Within this work we try to make a comprehensive list of the currently available RMPs mostly useful in the field of laboratory medicine, to present the reference measurement services having implemented some of these RMPs and to review how their performance may be regularly monitored.

Section snippets

Reference measurement procedures

The first point to address when looking for such a topic is where to find the relevant information. The Joint Committee for Traceability in Laboratory Medicine (JCTLM) database Working Group was charged for identifying, reviewing and publishing lists of available higher order certified reference materials, higher order reference measurement procedures, and reference measurement services of laboratories. The information is available through a dedicated website [2], which is regularly updated.

Reference measurement services

It is important to remember that a published RMP is only the basis and that has to be transformed into a standard operating procedure (SOP) in every calibration laboratory. As an example, in the case of HbA1c, the original description of the RMP was published as a research paper back in 1997 [15], and that only a few years later the SOP was fully described and published in another paper [11]. Indeed, the measurement design in the individual calibration laboratory has strong influence on the

Reference measurement services and evaluation of their performance

Most of the readers are familiar with EQAS procedures, which are regularly performed in order to monitor the long-term accuracy of routine methods. Various EQAS are present worldwide, but none of them is suited to evaluate the long-term performance of RMPs. In order to overcome this issue, ten years ago an external quality assessment scheme for reference laboratories in laboratory medicine was designed, and it is now regularly available through the JCTLM facility [16]. Essentially, specific

Conclusions

From the brief survey we have conducted, we have seen that for some measurands there are several RMPs listed in the JCTLM database. This is not a limit, on the contrary it is a richness, because there is absolutely no need to limit the number of RMPs as long as they meet the criteria of an RMP. For primary RMPs, the decisive factor is that the analytical measurement principle used allows the development of a RMP of higher/highest metrological order. If so, then it is quite possible that there

Acknowledgments

We acknowledge Dr. Anna Carobene and Dr. Elena Guerra (San Raffaele Hospital, Milano, Italy) for having shared with us their reports from the cholesterol network, and Dr. Cas Weykamp and Dr. Carla Siebelder (Queen Beatrix Hospital, Winterswijk, The Netherlands) for the permission of reproducing part of the report of the 2016 Shanghai study related to the IFCC network for HbA1c.

References (18)

  • Y. Chen et al.

    High accuracy analysis of glucose in human serum by isotope dilution liquid chromatography-tandem mass spectrometry

    Clin. Chim. Acta

    (2012)
  • International vocabulary of metrology

    Basic and General Concepts and Associated Terms (VIM)

    (2012)
  • G. Schumann et al.

    IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37°C

    Clin. Chem. Lab. Med.

    (2002)
  • G. Schumann et al.

    IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37°C

    Clin. Chem. Lab. Med.

    (2006)
  • E. Frusciante et al.

    Calculation of uncertainty of measurement of the catalytic activity concentration of alanine amminotransferase (ALT) in serum by the IFCC reference procedure

    Biochim. Clin.

    (2011)
  • N.G. Dodder et al.

    Certification of creatinine in a human serum reference material by GC-MS and LC-MS

    Clin. Chem.

    (2007)
  • S.H. Edwards et al.

    Proposed serum cholesterol reference measurement procedure by gas chromatography–isotope dilution mass spectrometry

    Clin. Chem.

    (2011)
  • B.N. Taylor et al.

    NIST Technical Note 1297: Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results

There are more references available in the full text version of this article.

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