Gram stain of bronchoalveolar lavage fluid in the early diagnosis of ventilator-associated pneumonia

To assess the usefulness of the Gram stain in the early diagnosis of ventil ator-associated pneumonia (VAP), we performed 146 protected specimen brushi ngs (PSB) and bronchoalveolar lavages (BAL) in 118 patients suspected of ha ving nosocomial pneumonia. Gram stain and counts of infected cells were per formed in ail samples from BAL fluid. A final diagnosis of pneumonia was es tablished in 51 patients and there was no infection in 95 cases. A threshol d of 2% of infected cells was used to distinguish between VAP and the group without VAP (sensitivity 86.3%, specificity 78.9%, positive predictive val ue 68.7% and negative predictive value 91.4%); there was good agreement wit h the final diagnosis (kappa statistic 0.616; concordance 81.5%). Regarding detection of bacteria using the Gram stain, we found a sensitivity of 90.2 %, specificity 73.7%, positive predictive value 64.8% and negative predicti ve value 93.3%; there was moderate agreement with the final diagnosis (kapp a statistic 0.586; concordance 79.4%). In the VAP group, we analysed the de gree of qualitative agreement between Gram stain and PSB quantitative cultu res: the correlation was complete in 51% (26 of 51 VAP), partial in 39.2% ( 20 of 51 VAP) and there was no correlation in 9.8% (five of 51 VAP). We con clude that the Gram stain is useful for rapid diagnosis of VAP but unreliab le for early adaptation of empiric therapy.