The study demonstrated the diagnostic utilities of the biomarkers procalcitonin, CRP, and CD64 for early diagnosis of VAP. CRP was found to be a sensitive biomarker more than CD64 and procalcitonin in early diagnosis of VAP allthrough the study period. The clinical pulmonary infection score (CPIS) was introduced to improve the specificity of clinical diagnosis and combines clinical, radiologic, physiologic, and microbiologic (culture of tracheal aspirate) data into a single numeric value. However, recent studies suggest that the CPIS has a lower specificity for the diagnosis of VAP.