World Thrombosis Day, 13 October 2021

Thrombosis is an underlying cause in one-in-four deaths globally.1

We’re opening our eyes to thrombosis and supporting World Thrombosis Day, an annual campaign that raises awareness of the often-underappreciated condition of thrombosis. Thrombosis is defined as the formation of a blood clot either in the artery (arterial thrombosis) or in a vein (venous thrombosis). A clot that forms and moves in the circulation is called an embolism.

Venous thromboembolism, or VTE, is an umbrella term for deep vein thrombosis, or DVT (a condition in which blood clots form most often in the deep veins of the leg), and pulmonary embolism, or PE (in which a blood clot travels in the circulation and lodges in the lungs which is potentially fatal). PEs often occur as the result of a DVT.

Thrombosis Risk Assessment and Prevention

Research suggests that VTEs are often preventable, and evidence-based prevention strategies can reduce the risk of clots developing in ‘at-risk’ individuals.2

To identify whether a patient is ‘at-risk,’ healthcare professionals conduct a VTE risk assessment, which is a tool or questionnaire that gathers information about a patient’s age, medical history, medications and specific lifestyle factors. Information is then used to discern a patient’s potential risk (e.g., high, moderate or low risk) for developing blood clots in the legs or lungs.

If you are admitted to a hospital and don’t receive an assessment, be proactive. Ask for one.

Risk Factors

VTE affects people of all ages, races and ethnicities, and occurs in both men and women. But certain factors and situations can increase the risk of developing potentially deadly blood clots and are helpful to keep in mind. High-risk factors include:3

  • Being in hospital for a prolonged period
  • Having surgery (especially hip, knee and cancer-related surgery)
  • Having cancer. Cancer patients are at 4-times higher risk than the general population of developing serious blood clots
  • Not moving for long periods of time (e.g., due to bed rest or long-duration travel)

In Europe, it has been estimated that VTE-related events kill more people every year than AIDS, breast cancer, prostate cancer and transport accidents combined.4 Awareness of the risks is the first step in prevention.

For more information on thrombosis visit www. or www.



  1. ISTH Steering Committee for World Thrombosis Day. Thrombosis: a major contributor to the global disease burden. J Thromb Haemost 2014;12(10):1580-1590.
  2. Schleyer AM, Robinson E, Dumitru R, et al. Preventing hospital-acquired venous thromboembolism: Improving patient safety with interdisciplinary teamwork, quality improvement analytics, and data transparency. J Hosp Med 2016;11 Suppl 2:S38-S43.
  3. NICE. Pulmonary embolism: What the the risk factors? Last revised in October 2020. Available at:
  4. Cohen AT, Agnelli G, Anderson FA, et al. Venous thromboembolism (VTE) in Europe. Thromb Haemost 2007;98:756-764.