As the country – and, at varying paces, the world – went into lockdown in March 2020 as a result of concerns surrounding COVID-19, no individual's life was left unaffected. Those testing positive, especially those who became severely ill or even lost their lives, are the obvious victims of the pandemic. Following them, most impacted were their loved ones and those providing care to them, particularly on the frontlines.
However, whatabout other people requiring treatment during the pandemic for non-COVID-related conditions? With severe limitations on healthcare resources and efforts to keep people safe at home, most elective procedures and any appointments deemed non-urgent were cancelled and many were not seeking help for non-COVID symptoms, partially out of fear of being exposed to COVID-19 in hospital and partially out of concern about placing additional burden on already severely strained services (British Heart Foundation, 2020).
Anticoagulation therapy
However, keeping hospital visits to a minimum has required other changes too. In March 2020, NHS England (2020) quickly devised a plan to switch patients who have previously had a blood clot and were on warfarin therapy to a direct oral anticoagulant (DOAC) in an effort to reduce face-to-face consultations with patients.
Warfarin, a vitamin K antagonist, is the most widely prescribed anticoagulant therapy, the goal of which is to prevent blood clotting by delivering the lowest effective dose of anticoagulant to maintain target international normalised ratio (INR), which measures how long it takes a person's blood to clot. The longer the blood takes to clot, the higher the INR, with most people on anticoagulant therapy having an INR of 2-3.5, meaning it takes their blood 2-3.5 times longer to clot than usual (NHS, 2019). The therapy aims to thin the blood to prevent blood clots, but not so much that bleeding risk increases, and getting this delicate balance right requires regular INR monitoring – a tall order during a pandemic with overextended healthcare resources.
Bumps in the road
Like most decisions made during the current pandemic, the decision to switch as many patients on warfarin therapy as possible to a DOAC to reduce the frequency of INR blood testing while still keeping them safe was made relatively quickly. It made logical sense, but without the time to consider all aspects or potential consequences of such a decision, it has not been without bumps in the road and there are many aspects to be weighed and considered in switching patients' anticoagulant therapy.
For example, a small (but according to Curtis et al (2021), ‘substantial’) number of patients who were switched to a DOAC continued on warfarin therapy as well (Robinson, 2021). Subsequently, a national safety alert was issued as well as guidance to health professionals to ensure that any patients being switched over stop their treatment with warfarin before starting on a DOAC in order to reduce any risk of over-anticoagulation and bleeding (Curtis et al, 2021; Medicines and Healthcare products Regulatory Agency (MHRA), 2020a; Robinson, 2021). DOACs, like warfarin, can have interactions with other medications so this is also worth bearing in mind (MHRA, 2020b) and there are many patient groups such as those with a prosthetic mechanical valve, those who are pregnant or breastfeeding and those with moderate-to-severe mitral stenosis, and others, for whom a DOAC is not an appropriate option (NHS England, 2020). For those who are deemed suitable for a switch, a phased approach is recommended over the 12-week INR monitoring cycle in order not to affect the supply chain for other patients (National Institute for Health and Care Excellence (NICE), 2020).
Interestingly, patients on anticoagulant therapy who have had changes made to their treatment have been reported to feel excluded from the decision-making process regarding their therapy (Pharmaceutical Journal, 2020) – and while it is acknowledged that the pandemic required emergency decision-making in the interest of public health and safety, it is still worthy of consideration. Researchers from the Canadian city of Vancouver, British Columbia, analysed interview notes from 388 patients with atrial fibrillation who were interviewed over the telephone every 3 months for 2 years. Of these, 56 patients had undergone a change to their therapy such as a switch or discontinuation. These patients not only had limited knowledge about their anticoagulant therapy, but they also had a generally negative attitude towards taking medicines, and the researchers highlighted that these experiences appeared to affect these patients' adherence to their anticoagulant therapy, and their perceptions of their care provider, as well as the healthcare system overall (Pharmaceutical Journal, 2020; Salmasi et al, 2020).
Patients with COVID-19
Patients on warfarin or any other vitamin-K antagonist require regular blood testing, which may be particularly frequent at the beginning of treatment as changes are made to ensure the correct dosage. However, another instance in which testing becomes especially important is when patients have symptoms of COVID-19 (eg high temperature, new continuous cough, loss of sense of smell or taste) or who have tested positive for the virus (MHRA, 2020b). Identifying this as soon as possible in order that patients receive the right care early on will reduce the risk of overcoagulating and bleeding (MHRA, 2020b). Furthermore, patients with COVID-19 may be prescribed antibiotics or antivirals, which may interact with warfarin or other vitamin-K antagonists (MHRA, 2020a).
Results of the switch
With the permission of NHS England, Curtis et al (2021) carried out a cohort study making use of routine clinical data from 24 million patients in England. Between March and May 2020, 12% of patients 20 000 of 164 000 on warfarin therapy were switched to a DOAC, most commonly edoxaban and apixaban (Curtis et al, 2021). A sharp rise in inappropriate coprescribing of warfarin and DOACs was observed in April 2020 (from 50-100 up to 246 per month) (Curtis et al, 2021). INR testing fell by 14% and a very small increase in elevated INR was noted during April 2020 compared with January 2020 (Curtis et al, 2021). Factors that were found by Curtis et al (2021) to be associated with patients switching from warfarin to DOACs in response to national guidance at the outset of the pandemic were older age, a higher number of recent INR tests, a diagnosis of atrial fibrillation, normal renal function and care home residency.