Clinical Value of Four Cytokines-Based Laboratory Parameters in Assessing Disease Severity in Patients with Severe Fever with Thrombocytopenia Syndrome.

Hyperactive immune responses are implicated in the disease severity, prognosis, and complications of Severe Fever with Thrombocytopenia Syndrome (SFTS). In this study, we analyzed the differences in cytokine levels and clinical characteristics between severe and non-severe SFTS patients, aiming to assess the validity of interleukin-6 (IL-6), interleukin-8 (IL-8), interferon-α (IFN-α), and interferon-γ (IFN-γ) as predictors of disease severity and clinical outcomes in patients with SFTS. We retrospectively analyzed the demographic characteristics, clinical features, and the aforementioned four cytokines in a cohort of 110 laboratory-confirmed SFTS patients between July 2024 and August 2025. A total of 110 patients with SFTS were enrolled in this study. According to our grouping criteria, 52 patients (47.27%) were classified into the severe group, and 58 patients (52.73%) were classified into the non-severe group. Serum samples from patients with severe and non-severe SFTS were analyzed to compare differences in some routine hematological parameters, liver function, cardiac enzymes, acute-phase proteins and viral load. We further analyzed the correlation between the serum levels of IL-6, IL-8, IFN-α and IFN-γ and the aforementioned clinical laboratory parameters in patients with SFTS. Receiver operating characteristic (ROC) curve analysis demonstrated that serum levels of IL-6 and IFN-γ have predictive value for the severity of SFTS (p < 0.05). As the cut-off value of IL-8 remained within the normal range, it was not predictive of disease severity. We evaluated the potential of IL-6 and IFN-γ as diagnostic and prognostic biomarkers for severe SFTS, which may facilitate patient risk stratification. In addition, we performed stratified analyses by age and sampling time for these four cytokines to examine whether these factors might introduce potential bias into the results. These findings suggest that cytokine profiling may offer adjunctive information for early risk stratification, but should not be used in isolation for clinical decision-making.