In a systematic review of the worldwide published data on venous thromboembolism (VTE) in COVID-19 patients, Cihan Ay, Stephan Nopp, and Florian Moik (Medical University of Vienna, Vienna, Austria) provide an in-depth analysis on the risk of VTE in patients hospitalised for COVID-19. While hospitalised patients at general wards have a VTE risk between 5–11%, the risk of developing deep vein thrombosis or pulmonary embolism in critically ill patients is 18–28%.
“From the beginning of the COVID-19 pandemic, studies reported an increased rate of thrombosis and pulmonary embolism in patients with COVID-19. On the basis of these reports, but without robust evidence from controlled interventional studies, global treatment strategies were developed, recommending more intense thromboprophylaxis strategies. Our study now offers a better understanding of the underlying risk and, therefore, aids in individual treatment decisions based on accurate risk assessment for the different patient groups,” reports Ay, the study’s principal investigator.
Within their review of the literature, the authors assessed a total of 5,951 studies published in the field of VTE in COVID-19. Of those, 86 studies were found eligible for inclusion and reported rates of thrombosis and pulmonary embolism in COVID-19 patients. After excluding additional studies due to underlying risk of bias in a structured assessment, 66 studies (28,173 patients) were found eligible to perform a meta-analysis to provide a robust estimate on risk of VTE in COVID-19.
The main findings are as follows: the overall VTE risk in hospitalised patients with COVID-19 is 14%, despite rigorous thromboprophylaxis regimens in most studies. Further, high heterogeneity in VTE rates was found between different patient subgroups. The rate was highest in patients admitted to intensive care units, with 23% of patients suffering VTE. Patients admitted to general wards suffered VTE in 8% of the cases. These findings underline the high risk of VTE in COVID-19 patients.
In addition, the authors specifically focused on estimating the risk of potentially life-threatening pulmonary embolism. The result: “This risk is considerably higher than in other comparable serious medical illnesses and ranges between 10 and 18% in COVID-19 patients requiring intensive care. Further, astonishingly, deep vein thrombosis was detected in almost half of the hospitalised COVID-19 patients who had been systematically screened for thrombosis using ultrasound.”
These findings underscore the strong impact of COVID-19 on the blood-clotting system. In addition, an exploratory analysis revealed that patients who developed deep vein thrombosis or pulmonary embolism during hospitalisation had significantly higher D-dimer concentrations at admission, a laboratory parameter that indicates an activated coagulation system. This finding might be used to help develop personalised, risk-stratified thromboprophylaxis strategies in the future.
In summary, the authors provide a detailed evaluation of the risk of VTE based on the severity of the disease. Future studies need to determine whether elevated D-dimer at hospital admission justifies intensification of anticoagulant treatment in hospitalised patients with COVID-19.