Diagnosis of ventilator-associated pneumonia: nonroutine tools for routine practice.

EDITORIAL During the past decade, remarkable efforts have been made to establish valid and reliable techniques for the diagnosis of ventilator-associated pneumonia (VAP). One of the most important findings consistently reported has been the limited value of traditional clinical criteria for the definition of pneumonia [1–3]. This has reinforced the need for the inclusion of additional diagnostic criteria derived from quantitative bacterial culture techniques. A histological diagnosis of pneumonia as independent reference for the calculation of diagnostic indices is only available in postmortem studies [4]. In fact, studies using postmortem histology as gold standard and fulfilling strict methodological requirements of lung tissue processing suggest that the diagnosis of VAP may be established in a realistic clinical setting with satisfactory accuracy by quantitative bacterial cultures [5–8]. It is, nevertheless, evident that postmortem studies select cases with ultimately fatal outcome, which do not reflect the whole spectrum of VAP. An irrefutable gold standard does not exist. As a result, clinical criteria remain crucial in routine practice as well as in studies evaluating different diagnostic techniques in the diagnosis of VAP. It has been suggested that studies evaluating clinical and radiological criteria in the diagnosis of VAP should include quantitative scoring, in order to reflect clinical judgement more accurately [9]. In support of this view, a clinical pulmonary infection score (CPIS), which attempts to grade the likelihood of the presence of pneumonia , was shown to achieve high concordance rates with quantitative culture results [10]. Thus, a clinical estimate (and/or scoring) of the probability of the presence of pneumonia remains a mainstay for the diagnosis of VAP. In light of the current controversy as to whether quantitative culture techniques are useful in routine practice [9, 11], two issues should be addressed: firstly, to what extent does aetiological diagnosis contribute independently to the diagnosis of VAP?; and secondly, can we rely on colony counts for treatment decisions? PUGIN et al. [10], using the above-mentioned CPIS consisting of six different clinical variables, reported a concordance of 93% between clinical and microbiological criteria for pneumonia. Similarly, AUBAS et al. [12] convincingly demonstrated the value of more complex clinical criteria than those traditionally used for the diagnosis of VAP. Thus, a quantitative culture result will independently establish the diagnosis of VAP in only a minority of cases. Accordingly, individual treatment decisions, in most cases, cannot rely exclusively on a quantitative culture result. This would imply standardized cutoff …