Feasibility for aggregation of commutable external quality assessment results to evaluate metrological traceability and agreement among results

External quality assurance in the era of standardization

Metrology in clinical chemistry aims to ensure the equivalence of measurement results from different in-vitro diagnostic measurement devices (IVD MD) for use in healthcare. The metrological traceability of measurement results to higher-order references is the cornerstone to achieving equivalent results. However, other fundamentals are also needed, including the commutability of reference materials and external quality assessment (EQA) materials for monitoring the equivalence of measurement results at the end-user level. This manuscript summarizes the findings and opinions expressed at the Joint Community for Traceability in Laboratory Medicine (JCTLM) workshop held on December 4-5, 2023. The workshop explored the relationship between EQA/proficiency testing and metrological traceability to higher-order references. EQA monitors the equivalence of measurement results from end-user IVD MDs. The workshop discussed the role and challenges of using EQA to improve and maintain the equivalence of measurement results. It also elucidated current developments in establishing the clinical suitability of laboratory results expressed as analytical performance specifications (APS).

Investigating the Current Harmonization Status of Tumor Markers Using Global External Quality Assessment Programs: A Feasibility Study

BACKGROUND

The harmonization status of most tumor markers (TMs) is unknown. We report a feasibility study performed to determine whether external quality assessment (EQA) programs can be used to obtain insights into the current harmonization status of the tumor markers α-fetoprotein (AFP), prostate specific antigen (PSA), carcinoembryonic antigen (CEA), cancer antigen (CA)125, CA15-3 and CA19-9.

METHODS

EQA sample results provided by 6 EQA providers (INSTAND [Germany], Korean Association of External Quality Assessment Service [KEQAS, South Korea], National Center for Clinical Laboratories [NCCL, China], United Kingdom National External Quality Assessment Service [UK NEQAS, United Kingdom], Stichting Kwaliteitsbewaking Medische Laboratoriumdiagnostiek [SKML, the Netherlands], and the Royal College of Pathologists of Australasia Quality Assurance Programs [RCPAQAP, Australia]) between 2020 and 2021 were used. The consensus means, calculated from the measurement procedures present in all EQA programs (Abbott Alinity, Beckman Coulter DxI, Roche Cobas, and Siemens Atellica), was used as reference values. Per measurement procedure, the relative difference between consensus mean for each EQA sample and the mean of all patient-pool-based EQA samples were calculated and compared to minimum, desirable, and optimal allowable bias criteria based on biological variation.

RESULTS

Between 19040 (CA15-3) and 25398 (PSA) individual results and 56 (PSA) to 76 (AFP) unique EQA samples were included in the final analysis. The mean differences with the consensus mean of patient-pool-based EQA samples for all measurement procedures were within the optimum bias criterion for AFP, the desirable bias for PSA, and the minimum bias criterion for CEA. However, CEA results <8 µg/L exceeded the minimum bias criterion. For CA125, CA15-3, and CA19-9, the harmonization status was outside the minimum bias criterion, with systematic differences identified.

CONCLUSIONS

This study provides relevant information about the current harmonization status of 6 tumor markers. A pilot harmonization investigation for CEA, CA125, CA15-3, and CA19-9 would be desirable.

Aggregated data from the same laboratories participating in two glucose external quality assessment schemes show that commutability and transfers of values to control materials are decisive for the biases found

OBJECTIVES

We report the results of glucose measurements performed during one year by the same measurement procedures (MPs) in 58 Norwegian hospital laboratories using control materials provided by external quality assessment (EQA) schemes from two different providers. The providers used materials with presumed vs. verified commutability and transfers of values using reference material vs. using a highest-order reference MP.

METHODS

Data from six Labquality and three Noklus glucose EQA surveys were aggregated for each MP (Abbott Alinity, Abbott Architect, Roche Cobas, and Siemens Advia) in each scheme. For each EQA result, percent difference from target value (% bias) was calculated. Median percent bias for each MP per scheme was then calculated.

RESULTS

The median % biases observed for each MP in the Labquality scheme were significantly larger than those in the Noklus scheme, which uses verified commutable control materials and highest-order reference MP target values. The difference ranged from 1.2 (Roche Cobas, 2.9 vs. 1.7 %) to 4.4 percentage points (Siemens Advia, 3.2 % vs. -1.2 %). The order of bias size for the various MPs was different in the two schemes. In contrast to the Labquality scheme, the median % biases observed in the Noklus scheme for Abbott Alinity (-0.1 %), Abbott Architect (-0.5 %), and Siemens Advia (-1.2 %) were not significantly different from target value (p>0.756).

CONCLUSIONS

This study underlines the importance of using verified commutable EQA materials and target values traceable to reference MPs in EQA schemes designed for assessment of metrological traceability of laboratory results.

HbA1c and biomarkers of diabetes mellitus in Clinical Chemistry and Laboratory Medicine: ten years after

Since its discovery in the late 1960s, HbA_1c has proven to be a major biomarker of diabetes mellitus survey and diagnosis. Other biomarkers have also been described using classical laboratory methods or more innovative, non-invasive ones. All biomarkers of diabetes, including the historical glucose assay, have well-controlled strengths and limitations, determining their indications in clinical use. They all request high quality preanalytical and analytical methodologies, necessitating a strict evaluation of their performances by external quality control assessment trials. Specific requirements are needed for point-of-care testing technologies. This general overview, which describes how old and new tools of diabetes mellitus biological survey have evolved over the last decade, has been built through the prism of papers published in Clinical Chemistry and Laboratory Medicine during this period.

Control externo de la calidad en medicina del laboratorio. Avances y futuro

Objectivos

Un programa de control externo distribuye las mismas muestras control entre varios laboratorios y evalúa los resultados obtenidos con un criterio común. El objetivo de este trabajo es resumir la evolución de los programas externos, poner de manifiesto los progresos conseguidos y deducir consecuencias prácticas para el laboratorio participante.

Métodos

El material es una breve revisión de los diferentes tipos de programas externos utilizados a lo largo de cuarenta años. El método es el análisis crítico de las ventajas e inconvenientes de cada modelo, a la luz de nuestra experiencia.

Resultados

A mitad del siglo XX se iniciaron los programas EQA, detectándose gran discrepancia entre resultados emitidos por distintos laboratorios. Se desarrollaron EQA en muchos países y se propusieron mecanismos para armonizarlos, como: establecer especificaciones derivadas de la variación biológica, promover el uso de métodos analíticos homogéneos, usar el EQA como herramienta educacional. A partir del 2000 se hacen importantes avances: asegurar el adecuado uso clínico de las pruebas del laboratorio, utilizar material control conmutable con el espécimen humano, armonizar los distintos modelos de EQA, promover una organización de cooperación entre organizadores de programas EQA.

Conclusiones

Participar en un EQA con controles conmutables y valores asignados por método de referencia certificado permite conocer la inexactitud real de los resultados y el impacto en las muestras de pacientes. Si se participa en programas con controles no conmutables solo se conoce si la prestación del laboratorio es similar a la de otros usuarios del mismo método analítico.

External quality control in laboratory medicine. Progresses and future

Objectives

An external quality control program distributes same control samples to various laboratories and evaluates results obtained with a common criterion. The aim of this work is to summarize the evolution of various types of external programs, to point out the progresses ant to preclude practical consequences of the participant laboratories.

Content

The material consists on a brief revision of the different types of external programs that have been used for the last forty years. The method is the critical analysis of the strong and weak points of each program model, from the light of our experience. External quality assessment (EQA) programs were initiated at half the XX century, evidencing big discrepancies among laboratory results. EQA were developed in various countries and some mechanisms to harmonize them were proposed: to establish common performance specifications derived from biological variation, to use EQS as educational tool. Since the 2000 important advances were seen: to focus EQA to assure the adequate clinical use of laboratory tests, to use commutable controls, to harmonize the different EQA models, to promote a forum for co-operation and exchange of knowledge on quality-related matters for EQA organizers.

Summary and Outlook

To participate in an EQA with commutable-reference method assigned values controls allows to know the real inaccuracy of results and their impact on patient' samples. To participate in a EQA with non commutable controls allows to know whether the individual laboratory performance agrees with that from other laboratories using same analytical method.

Lot-to-lot reagent verification: challenges and possible solutions

Lot-to-lot verification is an important laboratory activity that is performed to monitor the consistency of analytical performance over time. In this opinion paper, the concept, clinical impact, challenges and potential solutions for lot-to-lot verification are exained.