OpenSAFELY: Impact of national guidance on switching anticoagulant therapy during COVID-19 pandemic
Curtis HJ., MacKenna B., Walker AJ., Croker R., Mehrkar A., Morton C., Bacon S., Hickman G., Inglesby P., Bates C., Evans D., Ward T., Cockburn J., Davy S., Bhaskaran K., Schultze A., Rentsch CT., Williamson E., Hulme W., Tomlinson L., Mathur R., Drysdale H., Eggo RM., Wong AY., Forbes H., Parry J., Hester F., Harper S., Douglas I., Smeeth L., Goldacre B.
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.