Serial Monitoring of Interleukin-6 in Hospitalized COVID-19 Patients: A 7-Day Prospective Observational Study

A bstract Background: Severe COVID-19 is frequently associated with an excessive immune response, often characterized by a cytokine storm, in which interleukin-6 (IL-6) plays a crucial role. Elevated IL-6 levels have been correlated with disease severity, respiratory failure, and mortality. However, limited data exist on the temporal trends of IL-6 levels and their relationship with clinical outcomes over time. Objective: To evaluate serial IL-6 measurements over a 7-day period in hospitalized COVID-19 patients, analyzing their trends and association with clinical outcomes to assess IL-6 as a prognostic biomarker. Materials and Methods: This prospective observational study was conducted at Srinivas Institute of Medical Sciences and Research, Mangalore, from January 2022 to June 2022. A total of 100 hospitalized adult COVID-19 patients were recruited. Serial IL-6 levels were measured on Days 1, 3, 5, and 7 using chemiluminescent immunoassay. Clinical parameters, including oxygen requirements, intensive care unit (ICU) admission, mechanical ventilation, and inflammatory markers, were recorded. Statistical analysis was performed using t tests, ANOVA, and logistic regression models. Results: IL-6 levels were significantly higher in severe cases compared to mild/moderate cases (Day 1: 80 ± 30 pg/mL vs. 20 ± 10 pg/mL, P < 0.001). Persistently elevated IL-6 levels on Day 7 (>80–100 pg/mL) were strongly associated with ICU admission (75%) and mortality (50%) ( P < 0.001). IL-6 correlated positively with other inflammatory markers, including C-reactive protein and D-dimer, reinforcing its role in cytokine storm pathophysiology. Higher IL-6 levels on admission predicted the need for mechanical ventilation and poor clinical outcomes. Conclusion: Serial IL-6 monitoring provides valuable prognostic information in hospitalized COVID-19 patients. Persistently elevated IL-6 levels indicate poor prognosis and may guide early therapeutic interventions. Future studies should explore IL-6-targeted therapies and long-term patient outcomes.