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Dear Researcher,
The terms Long COVID (LC) or Post Acute Sequelae of SARS-CoV-2 infection (PASC) describe a condition that is characterised by the persistence of COVID-19 symptoms for at least 12 weeks after the onset of the disease. A study by Chen et al. (2021) estimates that around 40% of COVID-19 survivors suffer from LC. The symptoms of LC are clinically heterogeneous involving multi-organs/systems and range from fatigue, breathlessness, myalgia and headache to loss of memory and impaired concentration.
This heterogeneity in symptoms makes diagnosis of LC a challenge and highlights the very urgent need for diagnostic biomarkers. Such biomarkers would also be required in clinical trials of potential long COVID drugs where they could be used to indicate disease progression/regression.
Pro-inflammatory cytokines as blood based biomarkers for LC
A recent study in Nature Immunology by Phetsouphanh et al. (2022), analysed 28 potential serum markers in a cohort of LC affected individuals and compared them with control cohorts of age- and gender-matched recovered individuals without LC, unexposed donors and individuals infected with other coronaviruses.
The study found that patients with LC showed elevated expression of type I IFN (IFN-β) and type III IFN (IFN-λ1). The study used a log-linear classification model and defined a panel of inflammatory cytokines, IFN-β, PTX3, IFN-γ, IFN-λ2/3 and IL-6 that associated with LC with 78.5–81.6% accuracy.
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