The purpose of this study is to investigate the prevalence of venous thromboembolism in a regional health care system (Region Östergötland, Sweden) before and during the SARS-COV-2 pandemic. In a retrospective observational study, we will review patient data, diagnostic data and treatment data over a three-month period since the onset of the SARS-COV-2 pandemic. This data will be compared with data from the corresponding time frame during the years 2015 to 2019.

In the current SARS-COV-2 pandemic there is a concern about an increased risk of venous thromboembolism (VTE) concurrent with the infection, including both pulmonary embolism (PE) and deep venous thrombosis (DVT) (Klok et al. 2020; Cui et al. 2020; Helms et al. 2020; Leonard-Lorant et al. 2020; Poissy et al. 2020). International guidelines now recommend prophylactic anticoagulation for all hospitalized patients with a SARS-COV-2 infection in the absence of any contraindication (Thachil et al. 2020). The majority of the studies on VTE in SARS-COV-2 infections have been carried out in the ICU and show prevalence of VTE of between 20 and 30%.(Klok et al. 2020; Cui et al. 2020; Helms et al. 2020). This is a clear increase compared to the less than 10 % prevalence seen in other ICU patients (Muscedere, Heyland, and Cook 2007; Deborah Cook et al. 2005; D. Cook et al. 2000). However, a single center study on consecutive ICU patients with severe sepsis showed a prevalence of VTE of 37% (Kaplan et al. 2015) and another recent publication of patients with severe influenza A/H1N1 infection had a prevalence of VTE of 44% (Obi et al. 2019).

This raises the question whether the increase in VTE seen in recent publications of SARS-COV-2 infections is the result of the specific pathophysiology of the virus itself or the subsequent sepsis with multiorgan failure seen in most complicated and severe cases. The former would have large implications for patients treated outside the ICU and possibly outside hospitals (Thachil et al. 2020).

The aim of this study will be to investigate the prevalence of VTE in a regional healthcare system prior to, and during the SARS-COV-2 pandemic and the differences between ICU, hospitalized and outpatient cohorts.

Inclusion Criteria:

• Any patient that has done a Computer Tomography Angiography of the lungs between 1:st of March and 31:st of May each year from 2015 to 2020
• Any patient that has done a Ultrasound of the legs between 1:st of March and 31:st of May each year from 2015 to 2020
• Any patient with a new diagnosis of pulmonary embolism or deep venous thrombosis between 1:st of March and 31:st of May each year from 2015 to 2020

Exclusion Criteria:

• Incomplete diagnostic examination
• Follow-up examination of know acute VTE
• Primary investigation done outside the healthcare system
• Patient <18 years of age

For enrolment, we will consider all patients who have done a diagnostic examination for suspected VTE (pulmonary embolism och deep venous thrombosis) within the health care system of Region Östergötland during March, April and May 2015 through 2020. We will also include all patients with a new diagnosis of pulmonary embolism or deep venous thrombosis during the same time periods.

Region Östergötland/Östergötland County has a population of 465,495 (December 31, 2019).