Can Baseline IL-6 Levels Predict Long COVID in Subjects Hospitalized for SARS-CoV-2 Disease?

The immune response to infection plays a crucial role in the pathogenesis of COVID-19, but several patients develop a wide range of persistent symptoms, which is becoming a major global health and economic burden. However, reliable indicators are not yet available to predict the persistence of symptoms typical of the so-called long COVID. Our study aims to explore an eventual role of IL-6 levels as a marker of long COVID. Altogether, 184 patients admitted to the COVID Medicine Unit of the University Hospital in Palermo, Italy, from the 1st of September 2020, were analyzed. Patients were divided into two groups according to the IL-6 serum levels (normal or elevated), considering the serum IL-6 levels measured during the first four days of hospitalization. In our study, higher serum IL-6 levels were associated with a doubled higher risk of long COVID (OR = 2.05; 95% CI: 1.04-4.50) and, in particular, they were associated with a higher incidence of mobility decline (OR = 2.55; 95% CI: 1.08-9.40) and PTSD (OR = 2.38; 95% CI: 1.06-8.61). The analysis of our case series confirmed the prominent role of IL-6 levels in response to SARS-CoV-2 infection, as predictors not only of COVID-19 disease severity and unfavorable outcomes, but also long COVID development trends.