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Biomarkers to exclude the diagnosis of ventilator-associated pneumonia
  1. Michael A Matthay
  1. Correspondence to Professor Michael A Matthay, Departments of Medicine and Anesthesia, Cardiovascular Research Institute, University of California, 505 Parnassus Ave, M-917, Box 0624, San Francisco, CA 94143-0624, USA; michael.matthay{at}

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Ventilator-acquired pneumonia (VAP) is an important clinical problem that has been associated with substantial morbidity and mortality.1 However, the diagnosis of VAP can be particularly difficult,2–4 and surveillance programmes have not been markedly successful.5 ,6 The diagnosis of VAP can be difficult, in part, because new radiographic infiltrates can be secondary to aspiration, acute respiratory distress syndrome (ARDS) without pneumonia, or atelectasis.7 Typical criteria for the diagnosis of VAP include a new radiographic infiltrate, the presence of purulent tracheal secretions, hypothermia or hyperthermia, and/or a low or elevated peripheral white blood cell count. Some investigators and clinicians have used quantitative cultures of bronchoalveolar lavage (BAL) or tracheal aspirates with different thresholds of >103 or >104 colony-forming units to confirm the diagnosis with microbiological criteria. Pseudomonas aeruginosa and Staphylococcus aureus are the most common causes of VAP. Clinicians are usually compelled to initiate empiric antibiotic therapy in most patients with suspected VAP, pending a clinical response or the results of the microbiology cultures. However, quantitative culture results usually require 24–48 h. Thus, it would be helpful to have a method for either more rapidly diagnosing VAP, or at least excluding VAP that could be accomplished within a few hours after suspecting the diagnosis.

In this issue of Thorax, Hellyer …

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  • Funding US Department of Health and Human Services-National Institutes of Health R37 HL51856.

  • Competing interests None.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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