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Multicenter Study
. 2021 Nov;8(2):e001784.
doi: 10.1136/openhrt-2021-001784.

OpenSAFELY: impact of national guidance on switching anticoagulant therapy during COVID-19 pandemic

OpenSAFELY Collaborative; Helen J Curtis #  1 , Brian MacKenna #  1 , Alex J Walker #  1 , Richard Croker #  1 , Amir Mehrkar  1 , Caroline Morton  1 , Seb Bacon  1 , George Hickman  1 , Peter Inglesby  1 , Chris Bates  2 , David Evans  1 , Tom Ward  1 , Jonathan Cockburn  2 , Simon Davy  1 , Krishnan Bhaskaran  3 , Anna Schultze  3 , Christopher T Rentsch  3 , Elizabeth Williamson  4 , William Hulme  1 , Laurie Tomlinson  3 , Rohini Mathur  3 , Henry Drysdale  1 , Rosalind M Eggo  5 , Angel Yun Wong  3 , Harriet Forbes  6 , John Parry  2 , Frank Hester  2 , Sam Harper  2 , Ian Douglas  3 , Liam Smeeth  3 , Ben Goldacre  7
Affiliations
Multicenter Study

OpenSAFELY: impact of national guidance on switching anticoagulant therapy during COVID-19 pandemic

OpenSAFELY Collaborative et al. Open Heart. 2021 Nov.

Abstract

Background: Early in the COVID-19 pandemic, the National Health Service (NHS) recommended that appropriate patients anticoagulated with warfarin should be switched to direct-acting oral anticoagulants (DOACs), requiring less frequent blood testing. Subsequently, a national safety alert was issued regarding patients being inappropriately coprescribed two anticoagulants following a medication change and associated monitoring.

Objective: To describe which people were switched from warfarin to DOACs; identify potentially unsafe coprescribing of anticoagulants; and assess whether abnormal clotting results have become more frequent during the pandemic.

Methods: With the approval of NHS England, we conducted a cohort study using routine clinical data from 24 million NHS patients in England.

Results: 20 000 of 164 000 warfarin patients (12.2%) switched to DOACs between March and May 2020, most commonly to edoxaban and apixaban. Factors associated with switching included: older age, recent renal function test, higher number of recent INR tests recorded, atrial fibrillation diagnosis and care home residency. There was a sharp rise in coprescribing of warfarin and DOACs from typically 50-100 per month to 246 in April 2020, 0.06% of all people receiving a DOAC or warfarin. International normalised ratio (INR) testing fell by 14% to 506.8 patients tested per 1000 warfarin patients each month. We observed a very small increase in elevated INRs (n=470) during April compared with January (n=420).

Conclusions: Increased switching of anticoagulants from warfarin to DOACs was observed at the outset of the COVID-19 pandemic in England following national guidance. There was a small but substantial number of people coprescribed warfarin and DOACs during this period. Despite a national safety alert on the issue, a widespread rise in elevated INR test results was not found. Primary care has responded rapidly to changes in patient care during the COVID-19 pandemic.

Keywords: COVID-19; healthcare economics and organisations; medication adherence; stroke.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare the following: over the past 5 years, BG has received research funding from the Laura and John Arnold Foundation, the NHS National Institute for Health Research (NIHR), the NIHR School of Primary Care Research, the NIHR Oxford Biomedical Research Centre, the Mohn-Westlake Foundation, NIHR Applied Research Collaboration Oxford and Thames Valley, the Wellcome Trust, the Good Thinking Foundation, Health Data Research UK (HDRUK), the Health Foundation and the World Health Organisation; he also receives personal income from speaking and writing for lay audiences on the misuse of science. LS reports institutional grants from Wellcome, Medical Research Council (MRC), NIHR andUK Research and Innovation (UKRI). LT reports grants from Wellcome and MRC. KB holds a Sir Henry Dale fellowship jointly funded by Wellcome and the Royal Society (107731/Z/15/Z). RME holds grants from NIHR, MRC and HDRUK. RM holds a Sir Henry Wellcome Fellowship funded by the Wellcome Trust (201375/Z/16/Z). HF holds a UKRI fellowship. IJD has received unrestricted research grants and holds shares in GlaxoSmithKline.

Figures

Figure 1
Figure 1
Identification of patients. Flow chart illustrating how patients switching from warfarin to DOACs (and those switching back within the same period) were identified based on prescriptions issued. DOACs, direct-acting oral anticoagulants.
Figure 2
Figure 2
Patients newly initiated on DOAC repeats. Number of people having a new DOAC repeat prescription initiated per month (where the patient had no prior DOAC repeat ending within the previous 3 months), indicating whether or not patients had previously had a repeat prescription for warfarin (ending same month or within previous 3 months). DOAC, direct-acting oral anticoagulants.
Figure 3
Figure 3
Patients coprescribed warfarin and a DOAC. Number of patients having (A) both warfarin and a DOAC prescription issued on the same day, also indicating how many patients for whom one of those prescriptions was cancelled the same day (ie, its end date was equal to its start date); (B) both warfarin and a DOAC repeat prescriptions initiated on the same day (restricted to patients who also had at least one warfarin or DOAC prescription issued in the given month), also indicating how many patients for whom one of those repeat prescriptions was cancelled the same day (ie, its end date was equal to its start date). Patient counts are shown in online supplemental table S2. DOAC, direct-acting oral anticoagulant.
Figure 4
Figure 4
INR tests and recorded TTRs in warfarin patients. (A) Number of patients having an INR test, and the total number of INR tests carried out, per thousand warfarin patients. (B) Number of patients having a TTR recorded, and the total number of TTRs, per thousand warfarin patients. (C) Mean TTR value across warfarin patients tested. (D) Monthly rate of elevated INRs (as >8 and ≥8) recorded in warfarin patients per thousand warfarin patients and thousand patients having an INR test. INR, international normalised ratio; TTRs, time in therapeutic range.
See this image and copyright information in PMC

References

    1. The DataLab . Direct oral anticoagulants (DOACs) measure. OpenPrescribing. Available: https://openprescribing.net/measure/doacs/national/england/ [Accessed 30 Sep 2020].
    1. NHS England . Clinical guide for the management of anticoagulant services during the coronavirus pandemic, 2020. Available: https://web.archive.org/web/20200513044959/https://www.england.nhs.uk/co... [Accessed 20 Jul 2020].
    1. NHS England . Supply of additional direct oral anticoagulants (DOACs) during COVID-19, 2020. Available: https://www.worcslmc.co.uk/cache/downloads/C0517-DOAC-briefing-for-CCGs_...
    1. Warfarin and other anticoagulants – monitoring of patients during the COVID-19 pandemic. Available: https://www.gov.uk/government/publications/warfarin-and-other-anticoagul... [Accessed 16 Oct 2020].
    1. Curtis HJ, MacKenna B, Croker R. OpenSAFELY Codelists: direct acting oral anticoagulants (DOAC), 2020. Available: https://codelists.opensafely.org/codelist/opensafely/direct-acting-oral-... [Accessed 28 Oct 2020].

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