Predictive Performance of Inflammatory Markers for Severe Disease Progression in Measles: A Retrospective Cohort...

The recent European measles resurgence has driven record-high hospitalization, yet objective tools for early risk stratification remain scarce. This study evaluated the diagnostic accuracy of routine admission inflammatory biomarkers for predicting severe disease and prolonged hospitalization. We retrospectively analyzed 509 patients with laboratory-confirmed measles hospitalized during a Romanian outbreak (November 2023-August 2025). Severe disease was defined via a clinical composite endpoint (intensive-care admission, mechanical ventilation, supplemental oxygen, acute respiratory failure, or sepsis). Biomarker discriminative performance was assessed using receiver-operating-characteristic (ROC) curves, Youden-optimal cut-offs, and DeLong tests. Multivariable logistic and Cox proportional-hazards regression evaluated independent predictors of severity and time to discharge. The cohort exhibited a pediatric predominance (median age: 3.0 years; 20% infants) with an 82% unvaccinated rate; 33% developed severe disease. Interleukin-6 (IL-6) demonstrated superior diagnostic accuracy (AUC 0.863, 95% CI 0.820-0.898; cut-off ≥ 7 pg/mL, sensitivity 73%, specificity 93%), significantly outperforming ferritin (AUC 0.800) and conventional markers (all p < 0.001). Multivariable modeling established IL-6 and ferritin as the sole independent predictors of severity. All intensive-care admissions occurred exclusively for unvaccinated patients (5.0% vs. 0%). Severe disease, pneumonia, male sex, unvaccinated status and elevated C-reactive protein (CRP) independently predicted prolonged hospitalization. Admission IL-6 and ferritin serve as robust, independent prognostic biomarkers that accurately identify high-risk measles patients, providing objective criteria with which to optimize clinical triage and inpatient management during outbreaks.