(P-586) Association Between the Use of Oral Anticoagulant and Risk of Adverse COVID-19 Outcomes: An Opensafely Analysis

Background: While anticoagulants may be protective against severe COVID outcomes due to their anti-thrombotic effects, limited studies have investigated any potential impact of routine use of oral anticoagulants (OACs) on COVID-19 outcomes.

Objectives: To Investigate the associations between routinely prescribed OACs (warfarin and direct oral anticoagulant) and obtaining a COVID-19 test, a positive COVID-19 test, hospital admission due to COVID-19, and COVID-19 death respectively, versus non-use.

Methods: Working on behalf of NHS England, we conducted a cohort study using primary care data in England, linked to death registration data from Office for National Statistics, hospitalised data from Secondary Uses Service and SARS-CoV-2 antigen testing data from the Second Generation Surveillance System through OpenSAFELY. We identified people with atrial fibrillation and further limited the cohort to those who had a CHA₂DS₂-VASc score of 2 to reduce confounding by indication. Current OAC users were defined as those with OAC prescription(s) within 4 months before study start. We used Cox regression to estimate hazard ratios (HRs) for multiple outcomes respectively in current OAC users versus non-users, accounting for age, sex, co-morbidities, other medications and general practice.

Results: We included 52,289 current OAC users and 17,991 non-users. Current users were older, less likely to be current smokers and more likely to be obese and have had flu vaccination. We observed a lower risk of obtaining a positive COVID-19 test (adjusted HR, 0.69, 95% CI, 0.55–0.85), hospital admission due to COVID-19 with wide confidence interval (adjusted HR, 0.79, 95% CI, 0.57–1.10), and COVID-19 death (adjusted HR, 0.68, 95% CI, 0.47–0.98) associated with current use versus non-use. No difference in risk of obtaining a COVID-19 test (adjusted HR, 0.97, 95% CI, 0.92–1.01) associated with current use versus non-use were found.

Conclusions: Although we found a lower risk of COVID-19 death in current users versus non-users, a similar estimate for obtaining a positive COVID-19 test was also observed. Notably, the outcome of COVID-19 death reflected the probability of infection and once infected, COVID-19 deaths. Therefore, an observed lower risk of COVID-19 death was possibly due to a lower likelihood of getting a COVID-19 infection among current users versus non-users. These results suggest the COVID-19 pandemic does not provide any grounds for changing current guidance for those requiring anticoagulant therapy in routine care.