The missing piece: Who is responsible for ensuring clinical chemistry assays used in the UK are fit for purpose?

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.