Because BAL samples larger areas of lung, it as at least as sensitive as PSB and PTC (135). The sensitivity and negative predictive value of a culture for pneumonia are affected by the size of the sampling area and the amount of retrieved secretions. Bronchoalveolar lavage, which samples approximately 1 million alveoli, is estimated to recover 5 to 10 times the number of organisms obtained by PSB. Quantitative endotracheal aspirates would likewise be expected to provide more representative samples than PSB and PTC. Combining the results of PSB and BAL may increase sensitivity