Individuals with long COVID may be at greater risk for abnormal blood clotting

Issue: June 10, 2022

ByJennifer R. Southall

Individuals with long COVID may have a higher risk for abnormal blood clotting, especially those who have difficulties with basic exercise for more than 12 weeks after infection, according to a study published in Blood Advances.

The findings highlight a potential role for antithrombotic therapy in the management of these patients, researchers noted.

Rationale and methods

Long COVID, characterized by persistent fatigue, reduced exercise tolerance, chest pain, shortness of breath and cognitive slowing, is an increasingly recognized complication of acute COVID-19 infection, according to Nithya Prasannan, researcher in the department of hematology at University College London Hospitals NHS Foundation Trust in the U.K., and colleagues.

“Acute COVID-19 is strongly linked with increased risk [for] thrombosis and a prothrombotic state, quantified by elevated von Willebrand factor antigen:ADAMTS13 ratio, and is associated with severity of acute COVID-19 infection,” they wrote.

Investigators sought to examine whether patients with long COVID referred to a dedicated post-COVID-19 clinic experienced a prothrombotic state associated with symptom severity. The analysis included 330 patients (median age, 46 years; range, 18-88; 60% female), 97% of whom had symptoms for 3 months or more after acute COVID-19 infection.

Researchers assessed thrombotic risk and characterized patients as being in a prothrombotic state if they had significantly more von Willebrand factor antigen than ADAMTS13 in the bloodstream.

Eighty-four percent of participants (n = 276) completed exercise tests that included walking on a flat surface and/or repeatedly going from a sitting to standing position from a chair while wearing oxygen monitors. Researchers measured oxygen levels and tested participants’ blood before and after exercise to measure lactate levels.

Key findings

Results showed 28% of the entire cohort had a von Willebrand factor antigen:ADAMTS13 ratio of 1.5 or higher, which researchers considered to be raised. This was four times more common among patients with impaired exercise capacity, characterized by desaturation levels 3% or more and/or an increase in lactate level more than 1 from baseline on 1-minute sit to stand test and/or 6-minute walk test (P < .0001). Among those 56 patients, more than half (55%) had had a raised a von Willebrand factor antigen:ADAMTS13 ratio.

About one-quarter of all patients with long COVID had high factor VIII levels that ranged from 2.1 IU/mL to 5.1 IU/mL, and 18% had elevated von Willebrand factor antigen levels of 1.7 IU/mL to 3.3 IU/mL.

Implications

Looking ahead, Prasannan and colleagues plan to assess patients’ bloodwork using different research platforms during the course of their long COVID to assess how risk for thrombosis may change with progression of symptoms, according to a press release.

“I hope that people will view this research as a step forward in understanding what causes long COVID, which will hopefully help us guide future treatment options,” Prasannan said in the release. “I encourage people experiencing long COVID to participate in clinical trials when available because the more data we have, the better we can understand this condition.”