There was not a single instance when the BAL culture was positive with a corresponding negative endotracheal aspirate. ETA cultures yielded microorganisms in 37 episodes as compared to 29 by the reference standard and therefore only 29 episodes (78%) could be called definite VAP on endotracheal aspirates It has been shown that ETA has high sensitivity but low specificity for the diagnosis of VAP (22). So a sterile ETA assures the absence of VAP.In a study by Torres et al (32) of the 51 isolates on qualitative ETA only 29 (57%) correlated with same organisms growth on PSB (103 cfu/mL) and BAL (>103 cfu/mL). In another study (22) endotracheal secretions culture was positive in 70% of 30 pediatric cases. The concordance between reference standard (expert's opinion) and positive ETA was 57% (kappa 0.24). This high false positive rate in our as well as the studies cited above, could be explained by the bacterial colonization of the proximal airways observed in most patients in the ICU.