Same sample, different result: Variation in clozapine assay measurement in four UK laboratories

Matthew Atkins, James Fritz, Mary Rose Hilaire, David Taylor, Pathology Department, Oxford Health NHS Foundation Trust, Institute of Pharmaceutical Science, s College, Saladax Biomedical, Pharmacy Department, South London and Maudsley NHS FT

Therapeutic Advances in Psychopharmacology

Published online on August 17, 2026

Abstract

Therapeutic Advances in Psychopharmacology, Volume 16, January-December 2026.
BackgroundLaboratory measurement of clozapine blood concentrations is central to safe and effective treatment and is commonly assumed to be accurate and reproducible across providers. Chromatographic assays require batch-specific setup and are performed ...