Limitations of study. Lung tissue specimen is the best tool for the diagnosis of VAP (37) but not perfect as a gold standard (22). Lung tissue sample results may be negative if the patient is already on antibiotics and histological changes may be disseminated in the different segments of the lungs and not in a homogenous fashion (39). Studies have shown that sampling limited to one specimen from the lungs cannot exclude VAP (40, 41). Moreover the autopsy is difficult to use as gold standard in the pediatric population because of the mortality attributed to VAP is as low as 8% (42). In the present study the mortality due to VAP was 10%. In this study the bronchoscopic BAL culture (≥104cfu/mL) was used as reference standard. Compared with lung specimen cultures and histology, PSB (≥ 103 cfu/mL) and bronchoscopic BAL (≥ 104 cfu/mL) showed strong correlation in identifying the causative organisms (38). Moreover BAL appears to have an acceptable level of reproducibility of 75% (28). High concordance has been found for the presence (93%), type (86%) and quantity (78%) of bacteria in two protected BAL samples taken 2 hours apart (20).