AbstractBackground:Ventilator-associated pneumonia (VAP) is one of the most common nosocomial infections; however, its diagnosis remains difficult to establish in the critical care setting. We investigated the potential role of neutrophil CD64 (nCD64) expression as an early marker for the diagnosis of VAP.Methods:Forty-nine consecutive patients with clinically suspected VAP were prospectively included in a single-center study. The levels of nCD64, C-reactive protein (CRP), and serum procalcitonin (PCT) were analyzed for diagnostic evaluation at the time of intubation (baseline), at day 0 (time of diagnosis), and at day 3. The receiver operating characteristic curves were analyzed to identify the ideal cutoff values.Results:VAP was confirmed in 36 of 49 cases. In patients with and without VAP, the median levels (interquartile range, IQR) of nCD64 did not differ either at baseline [2.4 (IQR, 1.8–3.1) and 2.6 (IQR, 2.3–3.2), respectively; p=0.3] or at day 0 [2 (IQR, 2.5–3.0) and 2.6 (IQR, 2.4–2.9), respectively; p=0.8]. CRP showed the largest area under the curve (AUC) at day 3. The optimum cutoff value for CRP according to the maximum Youden index was 133 mg/dL. This cutoff value had 69% sensitivity and 76% specificity for predicting VAP; the AUC was 0.73 (95% CI, 0.59–0.85). The nCD64 and PCT values could not discriminate between the VAP and non-VAP groups either at day 0 or day 3.Conclusions:The results of this pilot study suggest that neutrophil CD64 measurement has a poor role in facilitating the diagnosis of VAP and thus may not be practically recommended to guide the administration of antibiotics when VAP is suspected.