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The IL-6 as an early marker of severe COVID-19

Background: Covid-19 is a disease associated with considerable morbidity and mortality in elderly population, however only fraction of infected will require hospitalisation. During first days of disease, until hypoxemia develops, it is difficult to identify the patients that will progress to severe respiratory failure. Interleukin 6 (IL-6) pays crucial role in Covid-19 pathogenesis and is a marker of disease severity. We explored the role of IL-6 as an early predictor for severe disease in elderly population.
Methods: We conducted a retrospective data analysis of cases of Covid-19, diagnosed during the outbreak in one long term care facility (LTCF) in Slovakia during first wave of Covid-19 in April 2020. Within 24 h after the diagnosis of Covid-19 in LTCF residents, clinical and laboratory screening (IL-6, C-reactive protein, blood count, D-dimer) was performed. Patients were monitored daily and those that developed hypoxemia were transferred to the hospital. We analysed the association between the IL-6 and other potential markers obtained during initial assessment and development of hypoxemia during follow up. Consequently, we determined the cut-off of the IL-6 able to predict the development of hypoxemia requiring oxygen therapy.
Results: Fifty-three patients (11 men, 42 women) with diagnosed Covid-19 were included in the analysis. 19 (53%) patients developed hypoxemia during the follow up. Patients who developed hypoxemia had significantly higher concentrations of IL-6, C-reactive protein, procalcitonin, fibrinogen, total bilirubin, aspartate aminotransferase and alanine aminotransferase at initial screening. We identified IL-6 as the most robust predictor of hypoxemia. The concentration of IL-6 > 24 pg/mL predicted the development of hypoxemia with the 100% sensitivity and acceptable specificity.
Conclusions: The concentration of IL-6 > 24 pg/mL measured during the first stage of the disease is good predictor of the development of hypoxemia requiring hospitalization in elderly population. Further studies are needed to evaluate the potential role of IL-6 as effective early predictor for hospitalisation in Covid-19 in general population and for other coronavirus variants.
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