Opinion Challenging the current hypothesis that thrombosis is responsible for the post-COVID-19 condition, 2024, Carson, Davey Smith, Garner et al

[SNT Gatchaman]

The main objection to the story is that the lumps in the pictures cannot have been there in the patients because they would have been centrifuged out.

But doesn't that argument also require that there's no such thing as platelet-poor plasma?

 

[Jonathan Edwards]

But doesn't that argument also require that there's no such thing as platelet-poor plasma?

Why?
At least some of the bits stuff they showed were much bigger than platelets and would need to be to be of any interest in embolisation.

Isn't platelet poor plasma plasma that has been spun hard enough to get rid of most of the platelets.

Platelet Poor Plasma

1. Centrifuge tube to obtain PPP.
2. Use a plastic transfer pipette to remove plasma (staying away from the buffy coat layer) and transfer top ⅔ of plasma to a plastic aliquot tube.
3. Centrifuge this aliquot tube at 1500 g for 10 minutes.

 

[Hutan]

There was also a letter to the editor responding to the rebuttal - "Reported particles are not blood clots, so anticoagulant drugs are not a plausible treatment" (18 October 2024). Sadly a lot of LC patients will dismiss the general critique due to the authorship; it would have been better coming from a group of respected haematologists rather than Garner et al.

Link | PDF

In their response, Kell and colleagues return to their research papers to question our forum article.2 We would refer Kell and his colleagues to our formal appraisal and bias assessment of these research papers, summarised in Table 1, one of which appears to remain unpublished.6 This table reports the data presented, highlighting the lack of individual sample data and limited efforts to quantify amyloid fibrin(ogen) particles. We assessed risk of bias using signalling questions across domains, in a method which itself is now published.7 This appraisal identified substantial concerns related to the collection and handling of samples, the experimental methods used, and the reporting of the results across all five papers.5 So the findings of the Cochrane review of laboratory studies still stand: these research papers fail to quantify the presence of amyloid fibrin(ogen) particles or present data beyond selected images.5

Pot, kettle.

As these particles are not blood clots, anticoagulant drugs are not a plausible treatment: it therefore challenges basic ethical principles to expose children and adults to triple therapy with anticoagulant drugs.

There is so much irony in that piece. They really don't seem to see that the people they support have a hypothesis at least as poorly founded as Kell et al, and have imposed a treatment regime on the very people that these authors claim to be concerned about.

I am interested though, in the idea that, as these clots aren't blood clots, anticoagulant drugs don't have an obvious rationale. I'm not sure if we have discussed that on our main thread for the microclot hypothesis.

It is a pity that they have not recruited some haematologists...
It intrigues me that haematologists have not said more about this. When I spoke to an eminent haematologist friend they seemed sceptical but perhaps not wanting to be seen to be saying so in public

I think the Icelandic doctor with a son with ME/CFS who has just joined the IACFSME is a haematologist.

 

[Nightsong]

It intrigues me that haematologists have not said more about this. When I spoke to an eminent haematologist friend they seemed sceptical but perhaps not wanting to be seen to be saying so in public

Maybe BSH should be made aware of the extent of it. SBNS intervened when there were unnecessary craniocervical fixation surgeries being carried out in the UK if I recall correctly.

 

[Jonathan Edwards]

I am interested though, in the idea that, as these clots aren't blood clots, anticoagulant drugs don't have an obvious rationale. I'm not sure if we have discussed that on our main thread for the microclot hypothesis.

I think their argument is naive and simplistic. Thrombosis and embolisation depend both on fibrin polymerisation and platelet aggregation, and can be contributed to by bacterial material as in endocarditis and even immunoglobulin in various forms of thrombotic vasculopathy like visual loss in myeloma.

For sure these are not technically clots and would not be even if they had formed in vivo, but if lumps of anything are floating about in blood anticoagulation might prevent secondary propagation of thrombus. She of the anticoagulants are directed at platelets, so not fibrin meshes per se.

 

[SNT Gatchaman]

At least some of the bits stuff they showed were much bigger than platelets and would need to be to be of any interest in embolisation.

They show activated platelets in PPP, which they describe as "spreading" and also "clumping".

So let's say that also allows for "microclot" objects that can be up to the same mass as platelets in the spun-down sample, and maybe up to the same size as activated platelets. Perhaps there could be a partial artefact such that with handling they tend to be more likely to aggregate. This might be similar to the clumping of the platelets. They might appear larger ex vivo than they truly are in circulation.

I think part of the explanation offered is capillary compromise, which might be on the basis of occlusion (ie thromboembolic), but they've also described the "microclots" as inflammatory, which could lead to slower capillary flow due to effects on the blood components, as well as endotheliitis/endothelial dysfunction.

The proteomics data still (to me) suggests that something is genuinely sequestering things like alpha-2-antiplasmin that they highlighted, that only increases with substantial fold-change following the double-digestion trypsinisation of the sample. This was discussed in this recent review presentation.

Regardless of whether the microclots as shown ex vivo are simply artifact, they absolutely could still represent a marker for (novel) pathological hypercoagulability. And their ex vivo size and deformability may relate to symptoms as discussed in May by Martin Kräter.

I am interested though, in the idea that, as these clots aren't blood clots

Resia Pretorius also defends the definition that they are clots earlier in that talk here: "How can you say this is a micro clot?".

She of the anticoagulants are directed at platelets, so not fibrin meshes per se.

You might have to clarify, but that sounds like you're saying anticoagulants are targeting platelets. DAPT (dual anti-platelet therapy, ie aspirin and clopidogrel) target platelets. DOAC (direct oral anticoagulant, eg apixaban or rivoroxiban) are factor Xa inhibitors.

Eg Wikipedia —

Apixaban is a highly selective, orally bioavailable, and reversible direct inhibitor of free and clot-bound factor Xa. Factor Xa catalyzes the conversion of prothrombin to thrombin, the final enzyme in the coagulation cascade that is responsible for fibrin clot formation. Apixaban has no direct effect on platelet aggregation, but by inhibiting factor Xa, it indirectly decreases clot formation induced by thrombin.

Rivaroxaban inhibits both free and bound Factor Xa in the prothrombinase complex. It is a selective direct factor Xa inhibitor with an onset of action of 2.5 to 4 hours. Inhibition of Factor Xa interrupts the intrinsic and extrinsic pathway of the blood coagulation cascade, inhibiting both thrombin formation and development of thrombi. Rivaroxaban does not inhibit thrombin (activated Factor II), and no effects on platelets have been demonstrated. It allows predictable anticoagulation and dose adjustments and routine coagulation monitoring; dietary restrictions are not needed.

 

[Jonathan Edwards]

They show activated platelets in PPP, which they describe as "spreading" and also "clumping".

Maybe that is a different preparation. Their methods are not well described.
But platelet aggregates would be spun out by centrifugation.

Perhaps there could be a partial artefact such that with handling they tend to be more likely to aggregate. This might be similar to the clumping of the platelets. They might appear larger ex vivo than they truly are in circulation.

Then the aggregation. would be ex vivo - however you try to play it.
Why should they look bigger. I have sent years doing fluorescence microscopy. Things don't suddenly 'look bigger' down a microscope!

but they've also described the "microclots" as inflammatory

But without a scrap of evidence. There is no clinical inflammation and acute phase markers are normal in longCovid. Remember that one of their studies supposedly of LC or ME/CFS (I forget which ) included something like 20% also having rheumatoid. The general methodology was disastrous.

which could lead to slower capillary flow due to effects on the blood components, as well as endotheliitis/endothelial dysfunction.

Sorry but this is just stuff they have up. This is my field. There is no such thing as endotheliitis. It has become a popular buzzword for people who never did any formal pathology training (as I did).

I am not denying that they may have hit on some shift in plasma protein levels of interest. What I am staggered by is the entirely ungrounded hyped statements they make all the time about their clot theory and its significance. I am not the only person to think this by any means. The haematologists I have spoken too reagard what I am saying here as obvious. They just think the whole thing is of no great interest.

 

[Sasha]

I am not the only person to think this by any means. The haematologists I have spoken too regard what I am saying here as obvious. They just think the whole thing is of no great interest.

The failure of peer review is scary.

 

[Jonathan Edwards]

Another thing that intrigues me is that Fox and Garner are Liverpool and so is Kell.
Is there some local infighting involved in all this?

 

[Trish]

For more discussion of microclots go to this thread:
The micro-clot finding in Long Covid — implications for the possible aetiology of ME/CFS