Plasma Host-Microbe Proteomics to Predict Complications in High-risk Febrile Neutropenia

Inclusion Criteria: * Adults (≥18 years). * Written informed consent provided by patient or legal representative. * Diagnosis of hematologic malignancy under induction chemotherapy, post-allogeneic hematopoietic stem cell transplantation, or CAR-T therapy. * High-risk febrile neutropenia (ANC ≤ 100 cells/mm³, expected duration ≥ 7 days, or significant comorbidities). * Fever defined as oral temperature ≥38.3 °C once or ≥38.0 °C for ≥1 hour. * Hospitalized or requiring immediate admission at the time of FN diagnosis. ´- Initial uncomplicated clinical presentation, with no previous infection or colonization by multidrug-resistant bacteria. * Eligible for initial monotherapy with broad-spectrum empirical antibiotic. * Availability for serial plasma sampling and clinical follow-up. Exclusion Criteria: * Age \<18 years. * Low-risk FN according to MASCC/CISNE criteria. * Initial sample collected after antibiotic administration. * Decline or inability to provide informed consent. * Any condition preventing safe participation or reliable sample collection. * Fever induced by noninfectious causes (considered as adjustment factor, not exclusion).