Thrombosis prevention in ambulatory patients with COVID-19

Venous thrombosis is a key vascular complication of COVID-19. Pharmacological thrombosis prevention with anticoagulant thromboprophylaxis is routine in hospitalised patients with COVID-19. However, in the absence of solid evidence, several scientists and scientific societies have suggested that a higher-than-standard dose might be given due to the high rate of thrombosis seen in COVID-19 inpatients.

Indeed, most patients, including the elderly, are initially treated at home in quarantine. Consequently, the vast majority of COVID-19-related deaths occur in the ambulatory setting. However, the routine use of thromboprophylaxis such as enoxaparin in outpatients is currently not recommended in the absence of any evidence from randomised controlled trials concerning its risk-benefit balance. This also applies to other frequent acute medical conditions, like influenza.

The present study hypothesises a potential benefit of thromboprophylaxis in COVID-19 patients, potentially reducing the number of hospitalisations, primarily due to thromboembolic complications, and the number of deaths among enoxaparin-treated patients. The OVID study will show whether prophylactic-dose enoxaparin is able to improve survival and reduce hospitalisations in about 1000 ambulatory patients aged 50 or older diagnosed with recent acute symptomatic COVID-19.

Enoxaparin is effective in preventing venous thromboembolism in medical patients with acute illness. This study is expected to reveal the beneficial effect of enoxaparin in the setting of COVID-19, due to its anti-inflammatory and antithrombotic profile. Key secondary objectives for this study are to determine whether enoxaparin administration versus no treatment reduces specific cardiovascular and thromboembolic complications, namely venous thromboembolism, myocardial infarction or stroke. Beyond COVID-19, this study will investigate, for the first time, the concept of ambulatory thromboprophylaxis in medically ill patients and represent the first large study on this topic.

The beneficial effects of enoxaparin remain purely hypothetical in the absence of clinical confirmation by interventional randomised controlled trials. As the vast majority of COVID-19 patients have been, and are being, treated in the outpatient setting, the results of the present study will have a major impact on the way this condition is treated and will be applicable to billions of people worldwide, particularly the frailest members of society.

Enoxaparin for primary thromoprophylaxis in ambulatory patients with coronavirus: the multicenter randomized controlled ovid trial