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Thrombosis and Post-COVID-19 Patient Recovery

By Hart Biologicals | 17th March 2021

With so many people experiencing blood clots (thrombosis) as a complication of COVID-19, we decided to explore the latest research and what is being done to support patients.  


COVID-19 and Blood Clotting

The link between thrombosis and COVID-19 has been established since May 2020, when the British Journal of Haematology reported clinicians were using CT scans to detect clotting of small vessels in the lungs of seriously ill COVID-19 patients. (1)

Coronavirus causes clotting issues in the tiny vessels in patient’s lungs, resulting in decreased blood and oxygen flow. (1) The changes are so small they are only visible from CT scans; however, they pose a significant risk to patient’s health. This requires the patient to receive blood-thinning medications, such as warfarin, to reduce the risk of clotting. (1)

However, recent research from the United States shines new light on the physiological issues surrounding coronavirus and the implications for patient treatment.


COVID-19 physiological impact on Factor V

Across the pond in the United States, the Massachusetts General Hospital and Harvard Medical School have undertaken a study to identify the physiological causes of blood clots in COVID-19 patients. (3) Their research suggests that COVID-19 could increase the amount of the factor V protein, also known as proaccelerin, in the bloodstream. (3)

Factor V is one of the many clotting factors in the body that helps blood maintain its clotting ability. (4) Factor V deficiency may be present without symptoms, but low levels can cause excessive blood loss after surgery or injury and can lead to haemorrhage. (4) However, increased levels, as found in the Massachusetts study, can equally upset the body’s equilibrium, and pose its own issues. Increased levels of factor V leads to a raised incidence of blood clotting and other thrombosis-related issues such as deep vein thrombosis or pulmonary embolism. (3) Factor V, as with other coagulation factors, is assessed through in vitro diagnostic reagents.

A study of one hundred COVID-19 patients in the intensive care unit found that nearly half exhibited abnormally high levels of the factor V protein. (2) Patients in this category were more likely to have blood clots in the lungs and veins, and deep vein thrombosis. (2) The study established a clear link between this and patient fatalities from COVID-19. (2) The research also suggests that monitoring factor V levels will be crucial in determining whether patients are progressing to a more serious medical situation. (2)


Clinical Trials for blood clotting treatment

One already published study, conducted in New York with 4,389 patients, found that patients receiving anticoagulation treatment had lower incidence of in-hospital death and intubation. (5) This could be a potential breakthrough moment for blood clotting issues surrounding COVID-19 and should be closely monitored by all those working in the haemostasis sector.

Research is also underway to assess the impact of anticoagulant medications as a potential treatment for COVID-19. (5) Research scientists at the National Institutes of Health have launched a series of clinical trials to examine the safety and effectiveness of anticoagulants to treat COVID-19 patients. (6)

The trials are set to be conducted in over one hundred sites globally. (6) They will consist of three patient groups: people who have been hospitalised with COVID-19, those with COVID-19 who haven’t been admitted to hospital, and people discharged from hospital after experiencing severe to moderate symptoms. This will provide vital evidence to guide clinical interventions for patients with COVID-19, especially those at risks of developing life-threatening blood clots. It is proposed that these results could lead to a suite of practical benefits such as understanding the differential factors between severe and moderate cases of COVID-19, while also helping us treat and assess the long-term effects of COVID-19.



  1. British Society of Haematology News. “Clear link” between COVID-19 and blood clotting – UK research team [Internet] 2020 Available online: - Article no longer available. 
  2. McNiff S. Elevated Blood Clotting Factor Linked to Worse COVID-19 Outcomes [Internet] 2020 [cited 5/10/2020] Available online:
  3. Stefely JA, Christensen BB, Gogakos T, Cone Sullivan JK, Montgomery GG, Barranco JP, Van Cott EM. Marked factor V activity elevation in severe COVID‐19 is associated with venous thromboembolism. American Journal of Hematology.
  4. Marcin, J (eds). Barwell. J. Factor V Deficiency. [Internet] 2017 [cited 5/10/2020] Available online:
  5. Nadkarni GN, et al. Anticoagulation, Mortality, Bleeding and Pathology Among Patients Hospitalized with COVID-19: A Single Health System Study. Journal of the American College of Cardiology. 2020 Aug 26.
  6. National Institutes of Health. NIH ACTIV initiative launches adaptive clinical trials of blood-clotting treatments for COVID-19  [Internet] 2020 [cited 5/10/2020] Available online: