Clinical Research Directory

Inclusion Criteria: * Age ≥ 65 years. * Hospital admission to the Internal Medicine or Infectious Diseases ward for a community-acquired acute respiratory infection. * Acute respiratory infection defined by the presence of at least two of the following criteria, with at least one being a clinical criterion: * Clinical criteria: new-onset cough or worsening of pre-existing cough; purulent sputum production or changes in usual sputum characteristics; new-onset dyspnea or worsening of pre-existing dyspnea; pleuritic chest pain; abnormal respiratory sounds (crackles, rhonchi, or wheezing); fever (temperature ≥ 38°C) or hypothermia (temperature \< 36°C). * Laboratory criteria: leukocytosis (white blood cell count \> 11,000/µL or neutrophil count \> 8,200/µL) or C-reactive protein ≥ 20 mg/L. * Radiological criteria: new pulmonary infiltrate or worsening of a pre-existing pulmonary infiltrate on chest imaging. * No alternative diagnosis considered more likely to explain the clinical presentation, according to the treating physician. Exclusion Criteria: * Charlson Comorbidity Index ≥ 5. * Imminent death with a life expectancy \< 24 hours. * Admission to the intensive care unit (ICU) directly from the Emergency Department or within the first 24 hours after admission to the hospital ward. * Diagnosis of a solid-organ or hematologic malignancy with active oncologic treatment within the previous 3 months. * Immune-mediated disease treated with immunosuppressive or immunomodulatory drugs. * Transplant recipient. * Treatment with prednisone ≥ 20 mg/day (or equivalent) for ≥2 weeks. * Human immunodeficiency virus (HIV) infection with an absolute CD4 count \< 200 cells/µL. * Profound neutropenia (\< 100 cells/µL). * Refusal to participate in the study or concurrent participation in another study. * Previous inclusion in this study.