Follow-up of Interleukin 6 and Other Blood Markers during the Hospitalization of COVID-19 Patients: A Single-Center Study

COVID-19 is a recent respiratory illness with high morbidity and mortality; therefore, the study and characterization of blood markers associated with the improvement or deterioration of COVID-19 patients are crucial. This study compared levels of interleukin 6 (IL-6), procalcitonin (PCT), D-dimer, cortisol, dehydroepiandrosterone sulfate (DHEA-S), c-reactive protein (CRP), 25-OH vitamin D, anti-SARS-CoV-2 IgG antibodies, and viremia in mild–moderate and severe–critical COVID-19 patients. In addition, the time course of blood markers was studied in severe–critical cases. The results show that levels of IL-6, PCT, D-dimer, and CRP, the cortisol/DHEA-S ratio, as well as positive viremia and anti-Spike IgGs were higher in severe–critical patients requiring hospitalization. During follow-up, most severe–critical cases displayed similar time patterns of IL-6 and viral load, whereas anti-SARS-CoV-2 antibody curves showed an inverse pattern. A decrease in IL-6 levels was associated with the improvement of COVID-19 patients, mostly through a reduced oxygen requirement. This preliminary study suggests that an increase in serum IL-6, PCT, D-dimer and CRP levels and the cortisol/DHEA-S ratio could support the selection of patients with poorer prognosis and the need for an intensive or alternative treatment. Additionally, changes in IL-6 during hospitalization were associated with changes in patient’s status mainly with a decrease in oxygen requirements, which indicates that serial measurements of IL-6 could predict the outcome of severe–critical patients with COVID-19 pneumonia.