EXTERNAL QUALITY ASSESSMENT 2


1.8 1.6 1.4 1.2 1


0.8 0.6 0.4 0.2 0


3.5 3


2020 2021 2022 2023 2024


Minimum Desirable Optimal


100 110 120 130 140 150 Overall mean (mmol/L) 160 170 180 2.5 2 1.5 1 0.5 0 100 110 120 130 140 150 Instrument mean (mmol/L) 160 170 180


Method A Method A Method B Method B Method C Method C Method D Method D Method E Method E Minimum Desirable Optimal


Fig 4. Precision profiles for sodium overall performance (left) and performance split by method. APS based on the current ‘best method’ has been proposed. 5


4.5 4


3.5 3


2.5 2


1.5 1


0.5 0


2020 2021 2022 2023 2024


Minimum Desirable Optimal


5


4.5 4


3.5 3


2.5 2


1.5 1


25 35 45 55 65 75 Overall mean (mmol/L)


Fig 5. Precision profiles for HbA1c overall performance (left) and performance split by method. APS based a hybrid of minimum TEa and ‘best method’ has been proposed.


relationship between performance in terms of SD or CV% and analyte concentration was rarely linear, and a hybrid model was proposed in these situations. For sodium and HbA1c, Model 2 was not achievable for all methods, and so APS based on a hybrid of Model 2 and Model 3 has been proposed. APS should be designed to provide performance assessment that best meets the needs of the service, whether used for screening, diagnosis or monitoring. Where clinical utility of the test includes two or more requirements, then the more stringent model is selected.


References 1


and Laboratory Medicine. Clin Chem Lab Med. 2015;53(6):833-835. doi:10.1515/cclm- 2015-0067


4 Horvath AR, Bossuyt PM, Sandberg S, et al. Seting analytical performance specifications based on outcome studies - is it possible?. Clin Chem Lab Med. 2015;53(6):841- 848. doi:10.1515/cclm-2015-0214


85 95 105


0.5 0


30


35


40


45 50


55 60


65


70 Instrument mean (mmol/L)


Boronate affinity 2020 Boronate affinity 2022 Boronate affinity 2024 POCT Im’chemistry 2021 POCT Im’chemistry 2023 Electrophoresis 2020 Boronate affinity 2022 Boronate affinity 2024 Immunochemistry 2021 Immunochemistry 2023 Ion exchange 2020 Ion exchange 2022 Ion exchange 2024 POCT Boronate 2022 POCT Boronate 2024 Desirable


Boronate affinity 2021 Boronate affinity 2023 POCT Im’chemistry 2020 POCT Im’chemistry 2022 POCT Im’chemistry 2024 Electrophoresis 2021 Electrophoresis 2023 Immunochemistry 2020 Immunochemistry 2022 Immunochemistry 2024 Ion exchange 2021 Ion exchange 2023 POCT Boronate 2021 POCT Boronate 2023 Minimum Optimal


75


80 85


90


95


PPi


Jones GRD, Albarede S, Kesseler D, et al. Analytical performance specifications for external quality assessment - definitions and descriptions. Clin Chem Lab Med. 2017;55(7):949-955. doi:10.1515/cclm-2017-0151


2 Fraser CG, Kallner A, Kenny D, Petersen PH. Introduction: strategies to set global quality specifications in laboratory medicine. Scand J Clin Lab Invest. 1999;59(7):477-478.


3 Sandberg S, Fraser CG, Horvath AR, et al. Defining analytical performance specifications: Consensus Statement from the 1st Strategic Conference of the European Federation of Clinical Chemistry


Ceri Parfit – R&D Clinical Scientist, Weqas Ceri Parfit has recently joined the team at Weqas as a Clinical Scientist Specialist in EQA, with over 12 years’ experience in laboratory medicine. Ceri is responsible for overseeing research projects within Weqas, developing new EQA programmes and assisting with quality improvement initiatives. She also supports the Duty Biochemist rota at the University Hospital of Wales in Cardiff, authorising laboratory results and providing clinical advice to healthcare professionals.


Annete Thomas – Director, Weqas Annete Thomas is a Consultant Clinical Biochemist at Cardiff and Vale University Health Board with over 40 years’ experience in laboratory medicine, over 20 years of which has been as Director of Weqas, a well-respected International EQA provider and Reference Measurement Laboratory. Annete is also the National Point of Care (POCT) Clinical lead for Wales, a seconded position to the Wales NHS Executive responsible for delivering the strategy plan for POCT. She is a member of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Task Force on Global Lab Quality and past chair of the IFCC Commitee on Analytical Quality. In 2019 she received the EQALM Adam Uldall Award for her contribution to promoting quality in laboratory medicine and the Healthcare Science Lifetime Achievement award from the Welsh Government.


Weqas operates as an independent organisation, hosted by Cardiff and Vale University Local Health Board, with over 50 years of experience in delivering global quality assessment programmes in laboratory medicine. contact@weqas.com www.weqas.com


May 2026 WWW.PATHOLOGYINPRACTICE.COM 47


SD (mmol/L)


SD (mmol/L)


SD (mmol/L) SD (mmol/L)


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