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The role of tiny blood clots in long COVID


We're going to turn now to one of the biggest medical mysteries of the coronavirus pandemic. We're talking about long COVID. Patients who have it report a wide range of symptoms that persist for weeks or months after they've recovered from an initial COVID infection. Those symptoms can include fatigue, brain fog, problems with breathing, depression, even hair loss. According to researchers at the University of Michigan, as many as 100 million people around the world have or have had long COVID. But doctors still don't know a lot about the condition.

That's where our next guest comes in. Resia Pretorius is professor of physiological sciences at Stellenbosch University in South Africa. She and her colleagues have been analyzing blood samples from long COVID patients since early 2020. And they've noticed many samples had something in common, microclots. So could these tiny blood clots help researchers better understand long COVID and possibly even develop ways to treat it? Professor Pretorius is with us now to tell us more. Professor, welcome. Thank you so much for talking with us.


MARTIN: So your research suggests microclots could turn out to have a key role when it comes to understanding long COVID. Could you just tell us a little bit more about what they are and, you know, how that might explain some of the symptoms that long COVID patients experience, especially the ones we hear the most about, like fatigue and brain fog?

PRETORIUS: Sure. When we speak about long COVID and microclots, I think we should just step back a second and speak about acute COVID. We have noted - we and others have noted that the vascular system and clotting is not working properly during acute COVID. So the dilemma with long COVID is that the percentage of individuals, up to 30%, never really get over the presence of these clotting abnormalities or physiological abnormalities when they are not infective anymore - so when they get over the normal five to 10 days of acute COVID. So during long COVID, these clots then just continue to be present.

MARTIN: Do you have any sense of why these microclots aren't breaking down like blood clots typically do in healthy individuals?

PRETORIUS: Inside the microclots that are present in these individuals' blood in circulation, there are various entrapped molecules, inflammatory molecules, that actually prevent the breakdown of the microclots. So although the body's trying very hard to break down these clots with the normal physiological processes, molecules entrapped in the microclots actually prevent it from breaking down.

Now, that is a massive issue because if these microclots are in circulation, it damages the vasculature, or your blood vessels, and in that process, prevents the cells to receive enough oxygen, causing then a failure of the coagulation system of oxygen to your cells. And that can be linked to all of the lingering symptoms that have been noted in long COVID.

MARTIN: Do you think your research could allow labs to start detecting long COVID in patients' blood and help doctors diagnose the condition? And one of the reasons I ask is that when we've interviewed people who've had long COVID, one of the things that they talk about is that people don't believe them. And they struggle with this sense of shame, which is, you know, almost as devastating for some people as the condition itself. So do you think that it's possible that the work would help people kind of home in on a diagnosis that people would accept, that - not just the medical community would accept but that people - regular people would accept or employers would accept so that people don't feel that they're constantly fighting this sense that they're malingering, for example?

PRETORIUS: That is exactly one of the major dilemmas that the millions of people suffering from long COVID all face daily. They are really severely ill. And if they go to a pathologist or their clinician and they do regular blood tests, all of the blood tests normally come back in the healthy levels. And therefore, many of the clinicians themselves say that these individuals suffering from long COVID, it is all psychological. And that is a major dilemma.

Just because we have not yet have a easy, available diagnostic marker for long COVID does not mean that the disease does not exist. So that is one of the most important key factors. So what we are - we and others, not only in South Africa, but a whole team of researchers and interested clinicians are working very hard to get the diagnostic where we can detect microclots in circulation. Only when we have got diagnostics, we can think about going into treatment regimes.

MARTIN: And, of course, treatment then is something that we would be very interested in. Does your research indicate some possible ways to treat long COVID? Is there anything you can tell us about that?

PRETORIUS: So one of the dilemmas with any treatment, whether you're talking about long COVID or acute COVID or any other condition, for that matter, is that the general clinical fraternity only believes data that comes from clinical trials. And currently, there is no proper clinical trials that is focused on long COVID. We are working on that with a group of U.S.A. researchers, as well as U.K. researchers. And we're trying to get trials going to see what conditions work and what conditions do not work. That is the most important thing that is needed. But for that to happen, obviously we need funds, and we need very big infrastructure to be able to do clinical trials.

MARTIN: And that leads me to my next question, which is, as we said earlier, it's estimated that millions of people have or have had long COVID. And with this current variant, this current surge fueled by this latest variant, it just seems logical that that number could rise. So much of the world's attention has been focused on vaccines - and certainly, rightly so - and then after that, of course, therapies. And rightly so. But do you think it's time for the world's kind of research, attention and resources to perhaps pivot to long COVID?

PRETORIUS: Absolutely. So as you mentioned, the focus have been, rightly so, on keeping people out of the hospital. And our health care facilities have really been under extreme stress. The dilemma is that many of the long COVID patients are at home, so they're not seen or heard of. And they're struggling on their own. So I think that's so, so important to focus our attention now on research and turning it to these very, very ill patients because if we do not do that in a few months' time, our economy will see the consequences and have a severe impact on our economies worldwide.

MARTIN: That was Resia Pretorius, professor of physiological sciences at Stellenbosch University in South Africa. We reached her via Skype. Professor Pretorius, thank you so much for sharing this expertise with us today.

PRETORIUS: Thank you very much for asking me.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.