Association of IL-1β, IL-6, IL-8, IL-12, TNF-α, and IFN-α With Severe Pediatric COVID-19 and Multisystem Inflammatory Syndrome

Background: The cytokine profile may provide clinically relevant information for assessing the inflammatory response in infectious diseases, including SARS-CoV-2. However, the threshold concentrations of cytokines associated with severe pediatric COVID-19 and cytokine patterns related to multisystem inflammatory syndrome in children (MIS-C), remain insufficiently characterized. Objectives: This study aimed to evaluate serum levels and exploratory threshold concentrations of IL-1β, IL-6, IL-8, IL-12, TNF-α, and IFN-α associated with severe pediatric COVID-19 and MIS-C, and to characterize cytokine patterns across different clinical forms of SARS-CoV-2 infection in children. Design: The cohort study included 200 children with laboratory-confirmed SARS-CoV-2 infection, including mild COVID-19 (n=106), moderate COVID-19 (n=72), and severe COVID-19 (n= 22), 40 children diagnosed with MIS-C, and 45 children with negative PCR and ELISA results for SARS-CoV-2. Participants were aged 1 month to 17 years (6.47±5.53 years), and none had received a COVID-19 vaccine at the time of inclusion. Methods: Serum concentrations of IL-1β, IL-6, IL-8, IL-12, TNF-α, and IFN-α were measured within the first 24 hours of hospitalization, before treatment initiation, using immunoenzymatic assays. Results: Cytokines associated with severe COVID-19 included IL-1β (cut-off 6.96 pg/mL), IL-6 (cut-off 68.37 pg/mL), IL-12 (cut-off 34.53 pg/mL), TNF-α (cut-off 60.63 pg/mL), and IFN-α (cut-off 26.96 pg/mL). All measured cytokines demonstrated adequate discriminatory performance for identifying MIS-C: IL-1β (cut-off 7.28 pg/mL), IL-6 (cut-off 100.64 pg/mL), IL-8 (cut-off 16.93 pg/mL), IL-12 (cut-off 34.91 pg/mL), TNF-α (cut-off 80.19 pg/mL), and IFN-α (cut-off 30.56 pg/mL). Random Forest analysis identified IL-1β and IL-8 as variables with the highest model-derived importance for COVID-19 severity classification, whereas age and sex showed lower model-derived importance than cytokine biomarkers. Conclusion: Cytokine profiling may support a more nuanced evaluation of hyperinflammatory immune responses in pediatric SARS-CoV-2-associated disease. However, its additional clinical value beyond routine clinical and laboratory markers requires validation in larger independent pediatric cohorts.