Prognostic value of albumin-based indices in predicting mortality and intensive care requirement in crimean–congo hemorrhagic fever: a comprehensive analysis of 1164 patients

Background: Crimean-Congo hemorrhagic fever (CCHF) is characterized by dysregulated inflammation and life-threatening endothelial dysfunction. In the absence of specific antivirals, identifying reliable biomarkers for risk stratification is critical. Objectives: This study evaluates the prognostic utility of indices derived from the ratio of inflammatory and hematological parameters to serum albumin—a surrogate marker of endothelial integrity—in predicting CCHF severity and mortality. Methods: This retrospective cohort study included 1164 adult patients with RT-PCR-confirmed CCHF (2015–2024). Ratios of platelet, WBC, neutrophil, lymphocyte, monocyte, CRP, ferritin, IL-6, and ESR to albumin were calculated from admission laboratory values. Indices were analyzed based on intensive care unit (ICU) requirement and survival. Results: ICU admission was required for 110 patients (9.4%), with a mortality rate of 8.0% (n=94). Except for ESR/albumin, all indices significantly differed between survivors and non-survivors. ROC analysis identified IL-6/albumin (AUC: 0.894) and ferritin/albumin (AUC: 0.873) as the strongest predictors of mortality. In addition, multivariate logistic regression analysis identified the IL-6/albumin ratio as the most powerful independent predictor of mortality (adjusted odds ratio: 7.58, p < 0.001). Conclusions: IL-6/albumin and ferritin/albumin ratios may serve as useful prognostic markers in CCHF, reflecting both hyperinflammation and vascular injury. These accessible and routinely measurable indices may contribute to early clinical triage and risk stratification. Keywords: Crimean–Congo Hemorrhagic Fever; Albumin-Based Indices; Mortality Prediction; IL-6/Albumin; Ferritin/Albumin