Abstract
Ventilator-associated pneumonia (VAP) is the most common healthcare-associated infection in the intensive care unit. Clinical, radiological and microbiological criteria are used to make the diagnosis, but there is no consensus definition, as no individual criterion or combination of criteria offer sufficient diagnostic accuracy to support their sole use in defining VAP. Neither invasive bronchoscopic sampling nor less invasive quantitative tracheal aspirate, conveys an advantage when making the microbiological diagnosis of VAP. Of the scoring systems and definitions presently in use, the Clinical Pulmonary Infection Score (CPIS) has been shown to be prone to inter-observer variability; the US Centers for Disease Control (CDC) National Healthcare Safety Network (NHSN) definition relies heavily on subjective clinical criteria, and the Hospitals in Europe Link for Infection Control through Surveillance (HELICS) criteria employ similarly subjective clinical criteria with five different possibilities for microbiological diagnosis. The use of these different diagnostic methods leads to marked variation in the reported incidence of VAP. Clinical practice requires an objective and transferable definition for VAP so that we can improve the reporting, monitoring and treatment of VAP.