Proximal deep vein thrombosis and pulmonary embolism in COVID-19 patients: a systematic review and meta-analysis

Background: COVID-19 appears to be associated with a high risk of venous thromboembolism (VTE). We aimed to systematically review and meta-analyze the risk of clinically relevant VTE in patients hospitalized for COVID-19. Methods: This meta-analysis included original articles in English published from January 1st, 2020 to June 15th, 2020 in Pubmed/MEDLINE, Embase, Web of science, and Cochrane. Outcomes were major VTE, defined as any objectively diagnosed pulmonary embolism (PE) and/or proximal deep vein thrombosis (DVT). Primary analysis estimated the risk of VTE, stratified by acutely and critically ill inpatients. Secondary analyses explored the separate risk of proximal DVT and of PE; the risk of major VTE stratified by screening and by type of anticoagulation. Results: In 33 studies (n = 4009 inpatients) with heterogeneous thrombotic risk factors, VTE incidence was 9% (95%CI 5-13%, I-2 = 92.5) overall, and 21% (95%CI 14-28%, I-2 = 87.6%) for patients hospitalized in the ICU. Proximal lower limb DVT incidence was 3% (95%CI 1-5%, I-2 = 87.0%) and 8% (95%CI 3-14%, I-2 = 87.6%), respectively. PE incidence was 8% (95%CI 4-13%, I-2 = 92.1%) and 17% (95%CI 11-25%, I-2 = 89.3%), respectively. Screening and absence of anticoagulation were associated with a higher VTE incidence. When restricting to medically ill inpatients, the VTE incidence was 2% (95%CI 0-6%). Conclusions: The risk of major VTE among COVID-19 inpatients is high but varies greatly with severity of the disease. These findings reinforce the need for the use of thromboprophylaxis in all COVID-19 inpatients and for clinical trials testing different thromboprophylaxis regimens in subgroups of COVID-19 inpatients.