New research sheds light on the risk of venous thromboembolism (VTE) in patients hospitalized for COVID-19.

The research, conducted at the Medical University of Vienna in Austria, found that the risk of VTE is considerably higher in COVID-19 than in other comparable serious medical illnesses. Deep vein thrombosis was detected in almost half of the hospitalized COVID-19 patients who had been systematically screened for thrombosis using ultrasound.

According to the researchers, 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 hospitalization 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 personalized, risk-stratified thromboprophylaxis strategies in the future.

“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,” says principal investigator Cihan Ay.

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 overall VTE risk in hospitalized 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.