ClusterVAP: Multicentre Proteomic Endotyping of Ventilator-associated Pneumonia

Inclusion Criteria: Adult patients (≥18 years) admitted to an intensive care unit (ICU). Receiving invasive mechanical ventilation. Undergoing bronchoalveolar lavage (BAL) or mini-BAL on clinical indication for suspected lower respiratory tract infection. New or worsening clinical signs compatible with lower respiratory tract infection within the preceding 24 hours, defined as the treating clinician's suspicion plus at least one of: Body temperature \>38 °C or \<36 °C. Visually purulent tracheal secretions. Signs of reduced oxygenation (e.g., increased FiO₂ and/or decreased arterial pO₂, increased positive end-expiratory pressure or driving pressure). Request for chest radiograph to investigate infection or new infiltrate. Initiation of antibiotic therapy targeting lower respiratory tract infection. Exclusion Criteria: BAL or mini-BAL performed solely for screening without suspicion of infection. Concurrent enrolment in the VAPmarkers study (reserved for external validation). Age \<18 years. Any condition that, in the opinion of the investigator, would preclude safe participation or confound study objectives.