by institution, but tends to be a combination of several of the following radiographic, clinical sign, and laboratory evidence: Temperature greater than 38 °C or less than 36 °C White blood cell count greater than 12,000/mm3 or less than 4,000/mm3 Purulent secretions, increased secretions, or change in secretions Positive tracheal cultures or bronchoalveolar lavage cultures Some sign of respiratory distress, such as shortness of breath, rapid breathing, abnormal breathing sounds when listening with stethoscope Increased need for oxygen on the ventilator Chest X-rays: at least two serial x-rays showing sustained or worsening shadowing (infiltrates or consolidations) Positive cultures that were obtained directly from the lung environment, such as from the trachea or bronchioles As an example, some institutions may require one clinical symptoms such as shortness of breath, one clinical sign such as fever, plus evidence on chest xray and in tracheal cultures. There is no gold standard for getting cultures to identify the bacteria, virus, or fungus that is causing the pneumonia, and there are invasive and non-invasive strategies for obtaining the culture sample. One non-invasive strategy collects cultures from the trachea of people with symptoms of VAP. Another is more invasive and advocates a bronchoscopy plus bronchoalveolar lavage (BAL) for people with symptoms of VAP. Both strategies also require a new or enlarging infiltrate on chest x-ray as well as clinical signs/symptoms such as fever and shortness of breath. There is no strong evidence to suggest that an invasive method to collect cultures is more effective than a non-invasive method. In addition, a quantitative approach to assessing the culture (performing a bacterial count of the pathogen that is causing the pneumonia) does not appear to be superior to a qualitative approach (determining the presence of the pathogen). In recent years there has been a focus on rapid diagnostics, allowing for detection of significant levels of pathogens before this becomes apparent on microbial cultures. Several approaches have been used, including using host biomarkers such as IL-1β and IL-8. Alternatively, molecular detection of bacteria has been undertaken, with reports that amplifying the pan-bacterial 16S gene can provide a measure of bacterial load. A trial of biomarker-based exclusion of VAP (VAP-RAPID2) has recently finished recruitment, and results are awaited (https://clinicaltrials.gov/ct2/show/NCT01972425). Blood cultures may reveal the microorganisms causing VAP, but are often not helpful as they are positive in only 25% of clinical VAP cases. Even in cases with positive blood cultures,