Over the past 50 years, External Quality Assessment (EQA) Schemes in the UK have changed from being overseen by the Department of Health and Social Security (DHSS) to a self-funding model post-1990, increasing competition among schemes. Despite reforms, there is no single source for assessing UK laboratories’ performance. Laboratories often use a single manufacturer, which can restrict laboratories to having to use a poor method for some assays. Regulatory changes like the EU In Vitro Diagnostics Regulation (IVDR) impact manufacturers. The Medicines & Healthcare products Regulatory Agency (MHRA) oversees assay performance, focusing on patient harm. Participation in EQA is mandatory for ISO 15189 accreditation, but the holistic quality of EQA services vary. Four cases studies (calcium, testosterone, paracetamol and total bilirubin) are presented that illustrate how the current systems are being used in practice. These show different elements of quality assurance, but crucially in all cases patient management will have been impacted. Most performance issues are manufacturer-related. EQA helps monitor assay quality, but gaps in oversight remain. Diagnostic reform is progressing, but differences in assay results pose risks. Laboratories must collaborate with stakeholders to ensure high-quality services. Mechanisms are needed to rectify sub-optimal assays. The current system can lead to patient misdiagnosis or incorrect clinical pathways. A mechanism is required to ensure accurate results for the public, within acceptable error margins, and at a sustainable cost for the NHS.
BelkWPSundermanFW. A survey of the accuracy of chemical analyses in clinical laboratories. Am J Clin Pathol1947; 17: 853–861.
2.
BuchtaCMarringtonRDe la SalleB, et al.Behind the scenes of EQA - characteristics, capabilities, benefits and assets of external quality assessment (EQA). Clin Chem Lab Med2025; 63: 844–858.
3.
BuchtaCMarringtonRDe la SalleB, et al.Behind the scenes of EQA- characteristics, capabilities, benefits and assets of external quality assessment (EQA). Clin Chem Lab Med2025; 63: 859–867.
4.
BuchtaCMarringtonRDe la SalleB, et al.Behind the scenes of EQA- characteristics, capabilities, benefits and assets of external quality assessment (EQA). Clin Chem Lab Med2025; 63: 868–878.
5.
BuchtaCDe la SalleBMarringtonR, et al.Behind the scenes of EQA-characteristics, capabilities, benefits and assets of external quality assessment (EQA). Clin Chem Lab Med2025; 63: 879–897.
6.
BuchtaCDe la SalleBMarringtonR, et al.Behind the scenes of EQA- characteristics, capabilities, benefits and assets of external quality assessment (EQA). Clin Chem Lab Med2025; 63: 898–915.
7.
MacKenzieF. Are the benefits of External Quality Assessment (EQA) recognized beyond the echo chamber?Clin Chem Lab Med2025; 63: 841–843.
8.
LewisSMJenningsRD. United Kingdom Quality Assessment Schemes annual report for 1987 prepared under the auspices of the DHSS advisory committee on assessment of laboratory standards. 1987.
9.
Supra-regional assay service - centres for analysis and clinical interpretation. https://www.sas-centre.org/, accessed 28/01/2025.
KahlesAGoldschmidHVolckmarAL, et al.Structure and content of the EU-IVDR : current status and implications for pathology. Pathologie (Heidelb)2023; 44: 73–85.
17.
CobbaertCCapoluongoEDVanstapelF, et al. Implementation of the new EU IVD regulation - urgent initiatives are needed to avert impending crisis. Clin Chem Lab Med. 2022; 60(1): 33–43.
18.
MarringtonRMacKenzieF. Understanding the limitations of your assay using EQA data with serum creatinine as an example. Clin Chem Lab Med2024; 62: 1824–1834.
19.
EvansCMacKenzieFMarringtonR. Variation in liver function testing and the effect of pyridoxal-5-phosphate on ALT, AST and FIB-4 results. Ann Clin Biochem2024; 61: 459–468.
20.
Birmingham Quality. UK NEQAS for Haematinic Assays Distribution 296. 2022.
21.
MajorRWShepherdDMedcalfJF, et al.The Kidney Failure Risk Equation for prediction of end stage renal disease in UK primary care: an external validation and clinical impact projection cohort study. PLoS Med2019; 16: e1002955.
SillarsALivingstoneRYatesTM, et al.Calcium requests in a primary care; an observational audit of biochemical requests and frequency of abnormal results. Clin Biochem2023; 113: 40–44.
28.
JayasenaCNAndersonRALlahanaS, et al.Society for Endocrinology guidelines for testosterone replacement therapy in male hypogonadism. Clin Endocrinol2022; 96: 200–219.
29.
JayasenaCNde SilvaNLO'ReillyMW, et al.Standardising the biochemical confirmation of adult male hypogonadism; a joint position statement by the Society for Endocrinology and Association of Clinical Biochemistry and Laboratory Medicine. Ann Clin Biochem2023; 60: 223–227.
30.
JayasenaCNde SilvaNLO'ReillyMW, et al.Standardising the biochemical confirmation of adult male hypogonadism: a joint position statement by the Society for Endocrinology and Association of Clinical Biochemistry and Laboratory Medicine. Clin Endocrinol2024; 101: 531–534.
31.
Monash University. International Evidence-based Guideline for the assessment and management of polycystic ovary syndrome. 2023.
32.
CaoZTBotelhoJCRejR, et al.Accuracy-based proficiency testing for testosterone measurements with immunoassays and liquid chromatography-mass spectrometry. Clin Chim Acta2017; 469: 31–36.
33.
van RossumHHvan WindenLJBergmanAM, et al.Current routine testosterone immunoassays are unsuitable for lowering the general castration cutoff recommendation to <0.7 nmol/l (20 ng/dl). Eur Urol Open Sci2023; 48: 98–100.
34.
DasguptaAWoodardKRamooB, et al.Technical note: significant positive bias in lower concentrations but negative bias in higher concentrations in testosterone measurement using beckman access immunoassay compared to a liquid chromatography-tandem mass spectrometry reference method. Ann Clin Lab Sci2024; 54: 258–261.
35.
ShiJBirdRSchmelingMW, et al.Using mass spectrometry to overcome the longstanding inaccuracy of a commercially-available clinical testosterone immunoassay. J Chromatogr B Analyt Technol Biomed Life Sci2021; 1183: 122969.
WatsonIProudfootA. Poisoning and Laboratory Medicine. 2002.
39.
HulzebosCVCamaraJEvan BerkelM, et al.Bilirubin measurements in neonates: uniform neonatal treatment can only be achieved by improved standardization. Clin Chem Lab Med2024; 62: 1892–1903.
40.
ThomasDHWarnerJVJonesGRD, et al.Total bilirubin assay differences may cause inconsistent treatment decisions in neonatal hyperbilirubinaemia. Clin Chem Lab Med2022; 60: 1736–1744.
41.
MarringtonRMacKenzieF. External quality assessment: using your EQA to support risk management. The Biomedical Scientist. IBMS Gazette, 2024.
42.
ISO/IEC 17043:2023 Conformity Assessment: general requirements for the competence of proficiency testing providers.
43.
MarringtonRMacKenzieF. Variation of eGFR reporting and CKD equations used in the United Kingdom. Ann Clin Biochem2023; 60: 328–333.
44.
MacKenzieFMarringtonR. Comparisons of real versus synthetic proficiency testing items. Accred Qual Assur. 2024; 29: 333–343.
45.
Birmingham Quality. UK NEQAS for Haematinic Assays Distribution 322. 2025.
46.
Birmingham Quality. UK NEQAS for Glycated Haemoglobins Distribution 487. 2024.
47.
SciacovelliLSecchieroSZardoL, et al.External quality assessment: an effective tool for clinical governance in laboratory medicine. Clin Chem Lab Med2006; 44: 740–749.
48.
LohTPMarkusCTanCH, et al.Lot-to-lot variation and verification. Clin Chem Lab Med2023; 61: 769–776.
49.
BadrickTBietenbeckACervinskiMA, et al.Patient-based real-time quality control: review and recommendations. Clin Chem2019; 65: 962–971.
50.
SchreierJFeeneyRKeelingP. Diagnostics reform and Harmonization of clinical laboratory testing. J Mol Diagn2019; 21: 737–745.
51.
VanstapelFOrthMStreichertT, et al.ISO 15189 is a sufficient instrument to guarantee high-quality manufacture of laboratory developed tests for in-house-use conform requirements of the European In-Vitro-Diagnostics Regulation. Clin Chem Lab Med2023; 61: 608–626.
52.
DirksNFAckermansMTMartensF, et al.We need to talk about the analytical performance of our laboratory developed clinical LC-MS/MS tests, and start separating the wheat from the chaff. Clin Chim Acta2021; 514: 80–83.
