Physicians and researchers are still trying to understand how the COVID-19 virus causes thrombotic complications. Endothelial damage is consistently found in autopsies of patients with COVID-19.

The von Willebrand factor antigen/ADAMTS13 ratio may contribute to immunothrombosis and predict mortality in patients with COVID-19, according to research published in Critical Care Medicine.

In the study, researchers suspected that an increase in von Willebrand factor multimers could exceed the capacity of ADAMTS13, contributing to immunothrombosis. They sought to measure whether endothelial damage from the disease leads to increased concentrations of von Willebrand factor and ADAMTS13 deficiency. They examined blood samples from 75 patients with COVID-19 and compared them to samples from 30 controls without the virus at hospitals in Germany.

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Patients with COVID-19 had mild to critical disease. The von Willebrand factor levels were 4.1 times higher in the patients with COVID-19 compared to controls without the virus, for a mean of 4.03 IU/mL. ADAMTS13 measures were similar between the group with COVID-19 and the control group.

However, the von Willebrand factor antigen to ADAMTS13 ratio was significantly lower in the group with COVID-19 (24.4 vs 82.0; P <.0001). The ratio continued to decrease with the severity of COVID-19. In the study cohort, the ratio also predicted higher mortality.

The authors noted similarity between the von Willebrand factor antigen/ADAMTS13 ratio in patients with COVID-19 to that of people with thrombotic thrombocytopenic purpura (TTP). With TTP, patients have a ratio below a level of 10, which is considered critical. No patients in the study were below the critical level of 10; however, the authors suggested that the von Willebrand factor antigen was at such high levels that it created a relative deficiency in 18.7% of patients.

The authors concluded that von Willebrand factor antigen and ADAMTS13 could reasonably be included in the diagnostic workup for patients with COVID-19.

Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


Doevelaar AAN, Bachmann M, Hölzer B, et al. von Willebrand factor multimer formation contributes to immunothrombosis in coronavirus disease 2019. Crit Care Med. Published online February 15, 2021. doi:10.1097/CCM.0000000000004918