Thrombotic risk in COVID-19: a case series and case-control study

Clin Med (Lond). 2020 Jul;20(4):e76-e81. doi: 10.7861/clinmed.2020-0228. Epub 2020 May 18.


Background: A possible association between COVID-19 infection and thrombosis, either as a direct consequence of the virus or as a complication of inflammation, is emerging in the literature. Data on the incidence of venous thromboembolism (VTE) are extremely limited.

Methods: We describe three cases of thromboembolism refractory to heparin treatment, the incidence of VTE in an inpatient cohort, and a case-control study to identify risk factors associated with VTE.

Results: We identified 274 confirmed (208) or probable (66) COVID-19 patients. 21 (7.7%) were diagnosed with VTE. D-dimer was elevated in both cases (confirmed VTE) and controls (no confirmed VTE) but higher levels were seen in confirmed VTE cases (4.1 vs 1.2 μg/mL, p<0.001).

Conclusion: Incidence of VTE is high in patients hospitalised with COVID-19. Urgent clinical trials are needed to evaluate the role of anticoagulation in COVID-19. Monitoring of D-dimer and anti-factor Xa levels may be beneficial in guiding management.

Keywords: COVID-19; D-dimer; deep vein thrombosis; pulmonary embolism; venous thromboembolism.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anticoagulants / therapeutic use
  • Betacoronavirus*
  • Biomarkers / blood
  • COVID-19
  • Case-Control Studies
  • Coronavirus Infections / blood
  • Coronavirus Infections / complications*
  • Female
  • Fibrin Fibrinogen Degradation Products / metabolism*
  • Heparin, Low-Molecular-Weight / therapeutic use
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Pandemics
  • Pneumonia, Viral / blood
  • Pneumonia, Viral / complications*
  • Retrospective Studies
  • Risk Factors
  • SARS-CoV-2
  • Venous Thromboembolism / blood*
  • Venous Thromboembolism / drug therapy
  • Venous Thromboembolism / epidemiology*
  • Venous Thromboembolism / virology


  • Anticoagulants
  • Biomarkers
  • Fibrin Fibrinogen Degradation Products
  • Heparin, Low-Molecular-Weight
  • fibrin fragment D