Controversies in the diagnosis of ventilator-acquired pneumonia

The appropriate investigation of patients with suspected VAP is controversial. Because it is unlikely that any new diagnostic technique will become available in the near future with better performance characteristics than those currently available, physicians need to tailor their diagnostic approach depending on individual patients and clinical scenarios. The most crucial factor in deciding which diagnostic approach to take is the influence that any test result would have on management. If preliminary screening tests, including Gram stain, are used to determine whether to start antibiotic therapy, invasive diagnostic techniques have an advantage over ETA. Quantitative cultures of respiratory specimens have a higher specificity than qualitative cultures and should be used if there is any possibility that a negative culture result would result in the discontinuation of antibiotic therapy. Physicians are caught between the need to treat VAP promptly with appropriate antibiotics and the undeniable problems of multidrug-resistant bacteria and their association with inappropriate antibiotic use. When clinically possible, a diagnostic strategy should be chosen that maximizes the possibility of limiting broad-spectrum antibiotic use. To give physicians greater comfort in the ability to withhold or discontinue antibiotics safely, further research is needed into the appropriate diagnostic strategies in different clinical settings that make this possible. The studies by Fagon et al and Singh et al are important steps in this direction.