Risk of symptomatic venous thromboembolism in mild and moderate COVID-19: A comparison of two prospective European cohorts

Background: Severely ill patients with SARS-CoV-2 have an increased risk of venous thromboembolism (VTE) i.e., deep vein thrombosis and pulmonary embolism. However, the VTE risk in patients with mild and moderate COVID-19, hospitalized or managed at home, remain uncertain. The aims of this study were to assess the rate and the risk factors symptomatic VTE, in patients with mild and moderate COVID-19 and to compare them to a cohort of similar patients without COVID-19.

Methods: Patients presenting to the emergency department (ED) of participating centers for confirmed or probable mild or moderate COVID-19 and not having acute VTE were included. This COVID-19 cohort was retrospectively compared to a prospective cohort of similar ED patients using propensity score matching. The main outcome was the rate of symptomatic VTE within the 28 days after ED presentation.

Results: A total of 2292 patients were included in the COVID-19 cohort. The 28-day incidence of symptomatic VTE was 1.3% (n = 29/2292, 95%CI: 0.9 to 1.8), 2.3% (n = 20/866, 95%CI: 1.5 to 3.5) in moderate COVID-19 patients and 0.6% (n = 9/1426; 95%CI: 0.3 to 1.2) in mild COVID-19 patients managed as outpatients. An age over 65 years and hospitalization were independent risk factors of VTE. After adjustment, patients in the COVID-19 cohort had an absolute increase in over symptomatic VTE risk of +1.69% (95%CI, 0.88 to 2.51) versus patients in the comparison cohort (n = 1539).

Conclusions: Patients with moderate COVID-19 presenting to the ED had a high risk of subsequent VTE.

Trial registration: Ethics committee of the CHU of Angers (N°2020/87).