In a new study, researchers reported on the frequency of venous thromboembolism (VTE) among more than 6000 patients who tested positive for infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the results of which were reported in Blood Advances.

According to the research team, infection with SARS-CoV-2 is thought to be linked to VTE, even in the setting of pharmacologic prophylaxis, and particularly in the context of critical illness with coronavirus disease 2019 (COVID-19).

However, the researchers noted that some studies have shown widely disparate levels of association of VTE with SARS-CoV-2 infection. The research team set out to quantify the association between the infection and VTE incidence in this large retrospective cohort analysis.

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This study used data from electronic health records of patients who were seen at a facility in the Ochsner Health System, based in New Orleans, Louisiana, from March 1, 2020, to May 1, 2020. The researchers evaluated treatments and outcomes with patients for whom the presence of SARS-CoV-2 infection was determined based on polymerase chain reaction-based analysis.

The median study follow-up was 14.6 days. A total of 3405 patients were treated only in the emergency department, and 2748 other patients were admitted to the hospital. Mechanical ventilation was provided to 637 patients, and 206 patients were treated with renal replacement therapy.

Among patients who were hospitalized, 3.1% had VTE, while 7.2% of those receiving mechanical ventilation experienced VTE. The mortality rate for hospitalized patients overall was 24.4%, and it was 27.9% for patients who developed VTE.

A total of 86 of the patients hospitalized with COVID-19 had new-onset VTE, of whom 45 (52.3%) received mechanical ventilation. The median peak D-dimer level in these 86 patients was 7.59 mg/mL (interquartile range, 3.07-32.24), and 4.6% of these patients had an international normalized ratio of greater than 1.5 on admission.

Most (89%) of the hospitalized patients who developed VTE were considered to have high-risk Padua scores during admission, reflecting high VTE risk, and 84 of the 86 patients received venous thromboprophylaxis. The researchers calculated the rate of VTE prophylaxis failure in these 86 patients to be 50%.

Patients receiving renal replacement therapy showed a high rate of frequent clotting in their dialysis circuits (22 patients) that was treated with heparin.

“Our findings, in combination with those previously published, suggest that VTE rates (and the rate of prophylaxis failure) in hospitalized patients with COVID-19 may be somewhat higher than expected,” wrote the researchers in their report. However, they also noted that the VTE rates in this study are not as high as those shown in some reports.


Hill JB, Garcia D, Crowther M, et al. Frequency of venous thromboembolism in 6513 patients with COVID-19: a retrospective study. Blood Adv. 2020;4(21):5373-5377. doi:10.1182/bloodadvances.2020003083