Switch from warfarin to DOACs to avoid INR monitoring exposure


By Nicola Garrett and Mardi Chapman

1 Apr 2020

Haematologists could consider switching some patients on warfarin to a DOAC in order to reduce the need for INR monitoring and with it, potential patient exposure to COVID-19.

The British Society for Haematology’s Haemostasis and Thrombosis task force said in a statement that regular INR monitoring of patients on warfarin was an essential part of safe anticoagulation and cannot be omitted during the social distancing that is required in response to the pandemic.

“Patients on oral anticoagulation with warfarin require regular INR testing which can be problematic at a time when we are trying to minimise visits to hospitals, GP surgeries and other testing facilities,” the UK advice said.

Clinicians are therefore advised to assess their patients for DOAC suitability, although the taskforce warns that not all patients will be able to switch. For example, warfarin should not be replaced in patients with heart valves, antiphospholipid antibody syndrome, renal failure, those requiring a higher than standard INR range of 2.0 – 3.0, or patients taking other medications known to interact with DOACs.

“This list is not exhaustive and there may be other reasons why a patient cannot be switched,” the UK task force said.

The advice also said that patients who were stably anticoagulated on warfarin with a time-in-therapeutic range (TTR) of >60% can generally have long INR test intervals of 8 weeks or in some cases longer.

“Patients in self-isolation because of possible COVID-19 exposure who are stably anticoagulated and would be due a routine test, can usually have the test safely postponed until after the period of isolation,” the task force added.

Associate Professor Huyen Tran, from Alfred Health told the limbic it was also very appropriate advice for Australian haematologists and his team were currently sorting through their patient lists.

“Obviously we are doing that – going through our lists and making sure that for the patients who are on warfarin that it is the only option for them, and for those patients who may be switched to a DOAC, we will talk to their clinician if we are not directly in charge of their clinical care.”

He said there was also good data for lengthening intervals between INRs in patients with TTR >60% – the gold standard when comparative trials were done.

Associate Professor Tran added that everyone was very busy and while reviewing patients on warfarin may not seem to be a top priority, it was very important.

“The next thing to do is put out a statement from the Society to try and remind people not to expose these patients by bringing them into hospital or the pathology service unnecessarily.”

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