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Point-of-care measurement of clozapine concentration using a finger-stick blood sample

Research output: Contribution to journalArticlepeer-review

David Taylor, Matthew Atkins, Robert Harland, Irina Baburina, James H. MacCabe, Salvatore J. Salamone, Philip McGuire

Original languageEnglish
Pages (from-to)279-283
Number of pages5
JournalJournal of Psychopharmacology
Issue number3
Accepted/In press2021
PublishedMar 2021

Bibliographical note

Funding Information: The authors declared the following potential conflicts of interest with respect to the research, authorship and/or publication of this article: David Taylor has received personal fees from H. Lundbeck and Janssen unrelated to this manuscript and has received payments from Mylan, a manufacturer of clozapine. Irina Baburina and Salvatore J. Salamone work for the manufacturer of the device, Saladax Biomedical, Inc. Dr MacCabe is supported by CRESTAR (CRESTAR project, ) EU-FP7 grant number 279227, by STRATA (MRC grant no.MR/L011794/) and by the National Institute for Health Research (NIHR), Biomedical Research Centre for Mental Health at the South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, Psychology and Neuroscience, Kings College London. Philip McGuire reports consultancy fees from Takeda, Janssen, GW Pharmaceuticals, Roche and Sunovion outside the submitted work. There are no other conflicts of interest. Publisher Copyright: © The Author(s) 2021. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors


Background: The use of clozapine demands regular monitoring of clozapine plasma concentrations and of white blood cell parameters. The delay between sending blood samples for analysis and receiving the results hinders clinical care. Point-of-care testing (POCT) can provide drug assay results within a few minutes. Aim: This study aimed to investigate the utility of a novel point-of-care device that can measure clozapine concentrations using capillary blood samples collected via a finger stick. Method: During a five-week period starting in June 2019 eligible patients were asked to provide a finger-stick capillary sample in addition to their usual venous blood sample. Samples were analysed by the novel point-of-care device and by the standard laboratory method. Capillary blood samples were tested by the MyCare™ Insite POCT analyser, and a quantitative measurement of clozapine concentration was provided within six minutes. Results: A total of 309 patients agreed to measurements by the two methods. Analysis revealed clozapine concentrations in venous blood as determined by the laboratory method ranged from 20 to 1310 ng/mL and by POCT from 7 to 1425 ng/mL. There was a strong positive correlation (R = 0.89) between the results from the venous and the capillary sample methods. The slope of the association between standard assay and MyCare™ Insite was 1.0 with an intercept of –21 ng/mL, indicating minimal bias. Conclusion: Clozapine concentrations can be accurately measured at the point of care using capillary blood samples collected via a finger stick. This approach may be more acceptable than venous sampling to patients and, with almost instant results available, more useful to clinicians.

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