Higher Incidence of Thrombotic Complications in Hospitalized Patients With SARS-COV-2 Virus Versus Influenza Virus Infections

Since the beginning of this year, accumulating studies reported findings of coagulopathy and high incidences of thrombotic complications in hospitalized patients with COVID-19 pneumonia. This was especially the case in patients admitted to the intensive care unit (ICU) but, to a lesser extent, also in ward-admitted patients. What is unknown is how the incidence of thrombotic complications in COVID-19 patients compares with that observed in hospitalized patients with other virus infections, including influenza, as some studies suggest that SARS-CoV-2 itself induces a specific procoagulant effect. Milou Stals, M.D., from Leiden University Medical Center in the Netherlands and colleagues studied whether COVID-19 was really associated with a higher incidence of thrombotic complications than is generally expected from a viral respiratory tract infection. She analyzed venous and arterial thrombotic complications in hospitalized COVID-19 patients admitted to the wards and ICUs of three Dutch hospitals. The venous thrombotic complications were compared with the incidence of venous thrombotic complications in hospitalized influenza patients, based on hospitalization data from Statistics Netherlands.

The study included 485 COVID-19 patients that were admitted to general wards and 178 admitted to the ICU (total number of patients equaled 579 because 84 patients had been admitted to both). In this study, the incidence of thrombotic complications in ward-admitted COVID-19 patients was lower than in ICU patients (34.1%), but still substantial, with a 30-day cumulative incidence of 5.3%. The 30-day cumulative incidences for venous thrombotic complications only were compared between hospitalized COVID-19 patients and hospitalized influenza patients. Interestingly, the incidence in COVID-19 patients was much higher than that in hospitalized influenza patients (17.8% versus 1.04%; ward and ICU combined).

Stals and colleagues concluded that the incidence of thrombotic complications in ward-admitted COVID-19 patients, while being lower than in ICU patients, was still substantial. Moreover, this incidence was considerably higher than that in hospitalized influenza patients, suggesting a possible SARS-CoV-2–specific effect. Further studies are needed to explore explanations for this large difference.