ClusterVAP: Multicentre Proteomic Endotyping of Ventilator-associated Pneumonia

Ventilator-associated pneumonia (VAP) is a common and serious infection in patients receiving mechanical ventilation in intensive care units. Current diagnostic methods are imprecise, leading to unnecessary antibiotic use and delayed treatment. The ClusterVAP study aims to identify biologically and clinically distinct subgroups of patients with suspected VAP by analyzing proteins in bronchoalveolar lavage (BAL) fluid using advanced proteomic techniques. This multicentre observational study will enroll approximately 400 adult patients from intensive care units in Sweden, France, Portugal, Denmark, and the United Kingdom. BAL or mini-BAL samples collected for clinical reasons will be analyzed to define "pneumoclusters" and explore their association with patient outcomes. The study will also identify candidate biomarkers that could support future diagnostic tools. No experimental treatments are given; all patients receive standard care. Results may improve diagnostic accuracy and guide personalized treatment strategies for critically ill patients.

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 \