An evaluation of the gram stain in protected bronchoalveolar lavage fluid for the early diagnosis of ventilator-associated pneumonia

We investigated the usefulness and reliability of the Gram stain value vers us quantitative cultures in the early diagnosis of ventilator-associated pn eumonia (VAP) using the protected bronchoalveolar lavage (PBAL). One hundre d four mechanically ventilated patients (age = 52 +/- 19; SAPS II = 38 +/- 15) with a strong suspicion of VAP were consecutively included. One hundred sixteen PEAL were performed and mini-bronchoalveolar lavage were analyzed using the Gram stain standard method and the conventional quantitative cult ure technique. VAP diagnosis was based on a positive quantitative culture o f mini-bronchoalveolar lavage fluid (cutoff greater than or equal to 10(3) CFU/mL). A final diagnosis of VAP was established in 67 patients and there was no infection in 49 cases. Regarding detection of bacteria using the Gra m stain, we found a sensitivity of 76.2%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 75.4%. There w as a good agreement with the final diagnosis (kappa statistic 0.73; concord ance 86.2%). The degree of qualitative agreement between Gram stain and qua ntitative cultures was analyzed in the VAP group: the correlation was compl ete in 39% (26 of 67 VAP), partial in 28% (19 of 67 VAP) and there was no c orrelation in 33% (22 of 67 VAP). We conclude that despite its overall "goo d agreement," the Gram stain is of limited use for the rapid diagnosis of V AP and unreliable for the early adaptation of empirical antimicrobial thera py when using the noninvasive PEAL procedure.