Analysis of thrombogenicity under flow reveals new insights into the prothrombotic state of patients with post-COVID syndrome, 2022

Analysis of thrombogenicity under flow reveals new insights into the prothrombotic state of patients with post-COVID syndrome
Adela Constantinescu-Bercu, Anna Kessler, Rens de Groot, Bertina Dragunaite, Melissa Heightman, Toby Hillman, Laura C. Price, Ewan Brennan, Raphael Sivera, Karen Vanhoorelbeke, Deepak Singh, Marie Scully

Background
Post-COVID syndrome (PCS) affects millions of people worldwide, causing a multitude of symptoms and impairing quality of life months or even years after acute COVID-19. A prothrombotic state has been suggested; however, underlying mechanisms remain to be elucidated.

Objectives
To investigate thrombogenicity in PCS using a microfluidic assay, linking microthrombi, thrombin generation, and the von Willebrand factor (VWF):a Disintegrin and Metalloproteinase with a Thrombospondin Type 1 motif, member 13 (ADAMTS13) axis.

Methods
Citrated blood was perfused through microfluidic channels coated with collagen or an antibody against the VWF A3 domain, and thrombogenicity was monitored in real time. Thrombin generation assays were performed and α(2)-antiplasmin, VWF, and ADAMTS13 activity levels were also measured.

Results
We investigated thrombogenicity in a cohort of 21 patients with PCS with a median time following symptoms onset of 23 months using a dynamic microfluidic assay. Our data show a significant increase in platelet binding on both collagen and anti-VWF A3 in patients with PCS compared with that in controls, which positively correlated with VWF antigen (Ag) levels, the VWF(Ag):ADAMTS13 ratio (on anti-VWF A3), and inversely correlated with ADAMTS13 activity (on collagen). Thrombi forming on collagen presented different geometries in patients with PCS vs controls, with significantly increased thrombi area mainly attributable to thrombi length in the patient group. Thrombi length positively correlated with VWF(Ag):ADAMTS13 ratio and thrombin generation assay results, which were increased in 55.5% of patients. α(2)-Antiplasmin levels were normal in 89.5% of patients.

Conclusion
Together, these data present a dynamic assay to investigate the prothrombotic state in PCS, which may help unravel the mechanisms involved and/or establish new therapeutic strategies for this condition.

Link | PDF (J Thrombosis and Haemostasis)

 

Researchers partly funded via UK NIHR / STIMULATE-ICP.

Concluding —

 

See related: Transcriptional reprogramming from innate immune functions to a pro-thrombotic signature by monocytes in COVID-19 in acute Covid.

 

See also Generation of potentially inhibitory autoantibodies to ADAMTS13 in coronavirus disease (2023)

 

1. Questions about how well the controls match
A. History of Covid-19 infection
So, there isn't a clear recovered control cohort - some of the controls may not have had Covid-19, only a vaccination. We aren't told how many of the controls had had COVID-19 in the last two years. We've seen that the biochemistry/immunology of people who have had a fairly recent Covid-19 infection differs from people who haven't, regardless of whether they report ongoing symptoms. Nearly two years though for the PCS cases is a long time though.

B. % of females
I haven't seen the sex ratios for the controls yet. 81% female in the PCS cohort.

It looks as though thrombotic generation parameters do differ by sex, so a lack of matching in the controls would be a problem.

2. Question about the heterogeneity of the PCS group

I think the potential heterogeneity of the PCS sample is a problem. 90.5% reporting breathlessness and 52.4% reporting chest pain suggests that it is possible that some of the PCS people had lung damage.

The uncertainties (whether there were more men in the controls, whether controls had had Covid-19; whether the PCS had overt tissue damage) take on significance when we hear that half the cohort had an increase in thrombin generation.

 

It doesn't look as though the a2-antiplasmin or fibrinogen levels were very remarkable - slightly raised fibrinogen. We don't know about the BMI of the PCS group (at least so far in the paper) - obesity can increase fibrinogen levels.

 

Five of the 21 PCS has elevated levels of VWF(Ag). That is something.

I guess a question is, are they the people with breathlessness and chest pains? do they have ongoing tissue damage? Do the levels correlate with other symptoms? Would people with no ongoing symptoms who have had Covid-19 fairly recently show similar levels? Is it possible that some of the PCS had had another more recent infection?

Most were only slightly elevated. Only 1 of the PCS with high fibrinogen levels also had high VWF levels.

 

It's not clear to me if this study was done with the same participants. There looks to be different numbers of people in each of the experiments.



There isn't that much difference in the platelets binding on the channel surfaces. Again, it seems that there is just a small proportion of PCS people producing unusual results.

 

I think that's a fair summary. It looks as if there is a subset of PCS group who have a prothrombotic tendency, but not all of the people labelled with PCS do.

I would like to know more about the PCS sample people in relation to their VWF and VWF(Ag):ADAMTS13 levels:

• their co-morbidities,
• BMI,
• sex,
• whether they are taking oral contraceptives (which can increase VWF)
• whether they had had additional Covid-19 infections after the one that triggered their long Covid symptoms (or any other infections or injuries closer to the time of the blood sample)
• whether they had any observable lung or heart damage
• their reported symptoms and severity

VWF can increase with physical (and reportedly emotional) stress. I'm not sure how quickly VWF levels change, presumably quickly in order to activate platelets to clot. It is conceivable that the stress of getting to the blood collection point might have caused an increase in VWF.

 

This is an interesting paper about VWF:
Performance Related Factors Are the Main Determinants of the von Willebrand Factor Response to Exhaustive Physical Exercise 2014

I'm not sure if the values can be compared, but the point is that VWF levels change a lot when people exert a lot. And the less fit people are, the more the VWF increases with exhaustive exertion.

It seems to me possible that what we are seeing here in the 2024 study subset with higher VWF levels is (partly) a response to the exertion of getting to the clinic in people whose capacity for exertion has decreased due to ME/CFS, lung or heart damage and/or deconditioning.