Evidence map›Paper›PMID 42431707›Full record

ArticleBMJ mental health2026

Prevalence and frequency of haematological testing in patients initiating clozapine in the USA.

Katsiaryna Bykov, Mufaddal Mahesri, Krista F Huybrechts, Lauren V Moran, Catherine S Hwang, Junyi Wang, Joyce Lii, Gita A Toyserkani, Esther H Zhou, Cynthia LaCivita and 3 more

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Article in BMJ mental health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.

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0cells of the map it votes in
1citing papers in PubMed
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1 · What the graph read from it

What it found

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2 · The registry

The trial behind it

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3 · Its place in the literature

Who cites it

1 citing paper in PubMed.

  1. Article
4 · The record

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5 · Who and what money

Authors and funding

13 authors.

Katsiaryna BykovDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA kbykov@bwh.harvard.edu.ORCID http://orcid.org/0000-0003-3336-5412
Mufaddal MahesriDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Krista F HuybrechtsDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Lauren V MoranDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Catherine S HwangDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Junyi WangDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Joyce LiiDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Gita A ToyserkaniOffice of Surveillance and Epidemiology, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA.
Esther H ZhouOffice of Surveillance and Epidemiology, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA.
Cynthia LaCivitaOffice of Surveillance and Epidemiology, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA.
Gerald J Dal PanOffice of Surveillance and Epidemiology, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA.
Aaron S KesselheimDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Ameet SarpatwariDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.ORCID http://orcid.org/0000-0001-5043-6206

Funding

Novel approaches to identify and quantify the impact of drug-drug interactions in older adults with diabetes, with a focus on multimorbidity and polypharmacyK01AG068365 · NIA · BRIGHAM AND WOMEN'S HOSPITAL · PI BYKOV, KATSIARYNA · 2021 to 2025
$621k
NIA NIH HHS K01 AG068365
6 · The paper itself

Abstract

backgroundUntil June 2025, individuals initiating clozapine in the USA were required to undergo routine haematological testing in accordance with the Clozapine Risk Evaluation and Mitigation Strategy (REMS) programme. Although the Clozapine REMS programme was eliminated in June 2025, clinical and prescribing recommendations on testing remained intact. Little is known, however, about adherence to testing requirements in practice.

objectiveThe aim of this study was to assess the prevalence and frequency of haematological testing in patients on clozapine.

methodsA cohort study using three US health insurance claims databases (1 January 2000-31 March 2022) assessed (1) proportion of individuals with at least one haematological test (white blood cell count with differential) prior to clozapine initiation and (2) frequency of testing (number of tests per 30 days of follow-up) during months 0-6, 7-12 and 13-24 of clozapine therapy. Tests were identified based on billing codes; patients hospitalised during the assessment period were assumed to have received testing.

findingsA total of 62 003 clozapine initiations (mean (SD) age, 36 (15) years; 57% male) were identified, of which 71% were preceded by testing within 60 prior days. The mean (SD) testing rate while on therapy was 2.2 (1.8) tests per patient for each 30-day period during the first 6 months of treatment, 2.0 (1.8) tests per 30 days during months 7-12 and 1.5 (1.4) tests per 30 days during months 13-24.

conclusionsIn this study of individuals initiating clozapine in the USA, haematological testing was completed at a lower-than-expected rate prior to clozapine initiation and during the first 6 months of treatment but was in accordance with testing requirements thereafter. CLINICAL IMPLICATIONS: Although clozapine drug labelling recommends routine haematological testing, especially during the first 6 months of treatment, such testing may not consistently occur. Reasons for less-than-recommended testing frequency should be further investigated.

Indexed as

Antipsychotic AgentsClozapineHematologic TestsSchizophreniaAdultCohort StudiesFemaleHumansMaleMiddle AgedPrevalenceUnited StatesAntipsychotic AgentsClozapinePsychotherapySchizophrenia

Identifiers

PMID42431707
PMCPMC13358246

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.