Qualitative cultures of tracheal aspirate (TA) is not a specific diagnostic method because of the lower respiratory tract colonization and a high percentage of false-positive results [48, 68] . However, investigators reported that quantitative cultures of TA have equal diagnostic accuracy to the other invasive techniques [69] [70] [71] [72] [73] . In a recent study, quantitative cultures of TA were compared with plugged telescoping catheter (PTC). The specificity of TA was similar to PTC when a cut-off point of 10 6 cfu/mL or higher was used, although the sensitivity of TA at ≥ 10 6 cfu/mL was lower than PTC. But when a cut-off point of 10 5 cfu/ mL was used, the sensitivity of TA was not statistically different from that of PTC [74] . Although, quantitative cultures of TA is non-invasive, inexpensive and a simple method, it has some risks, that if the cut-off value ≥ 10 6 cfu/mL is used, sensitivity will be low and some patients with VAP may not be identified or when the cut-off value ≥ 10 5 cfu/mL is used, unnecessary antibiotic treatment will be given because of low specificity [75] .