Monday, January 30, 2023

Can’t just “get over it”: Long COVID

Many people have experienced lingering problems after recovery from COVID infection, a condition known as long COVID or post-COVID.  A Norwegian study found that symptoms persisted for 6 months in most patients (189 of 312), including most young adults.  (‘Long COVID’ preferred because ‘post-COVID’ is ambiguous.) 

What is long COVID? There are many symptoms, led by fatigue, loss of smell/taste, breathlessness, and cognitive impairment, with no obvious common cause or relationship. Increased blood clotting (prothrombotic) has been suspected, suggested by the involvement of the receptor for the COVID-19 spike protein, ACE2, but strong evidence and mechanisms have been lacking.  

These authors tested the blood of 21 patients with post-COVID syndrome (PCS), averaging nearly 2 years after onset of infection. They modeled real blood flow through vessels by collecting blood samples (treated with the anti-coagulant citrate) and sending it through narrow tubes coated with particular proteins. They looked at the binding of platelets, which are abundant cellular products that initiate blood clots upon being triggered by binding collagen. They found striking increases in platelets binding to collagen (shown, Figure 1a top panel). Antibodies against von Willebrand factor (VWF) produced equivalent binding though apparently with different patterns (middle panels). 

Figure 1A: Binding of platelets (yellow) from healthy control blood (left) or PCS blood (right) to collagen (top), anti-VWF (middle), or VWF (bottom).

Although these intriguing findings await confirmation (by others) and follow-up, of course, they are of the utmost importance given the enormous impact of COVID.  

Constantinescu-Bercu A, Kessler A, de Groot R, Dragunaite B, Heightman M, Hillman T, Price LC, Brennan E, Sivera R, Vanhoorelbeke K, Singh D, Scully M. Analysis of thrombogenicity under flow reveals new insights into the prothrombotic state of patients with post-COVID syndrome. J Thromb Haemost. 2023 Jan;21(1):94-100. doi: 10.1016/j.jtha.2022.10.013. Epub 2022 Dec 22. PMID: 36695401; PMCID: PMC9773628.  

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