Background

Ventilator-associated pneumonia (VAP) is an important nosocomial infection among patients on mechanical ventilation. Modified clinical pulmonary infection score (CPIS) is used widely for diagnosis of VAP. There is a need for a non-invasive microbiological technique for diagnosis of VAP. Therefore, we performed a prospective study to determine the diagnostic value of semi-quantitative and quantitative cultures of endotracheal aspirates (EA) in VAP.

Method

During a period of 15 months from October 2006 to December 2007, a prospective observational cohort study was conducted at a tertiary care hospital. Semi-quantitative and quantitative cultures of EA were performed for patients with VAP.

Results

A total of 200 patients were prospectively evaluated, of whom 42 (21%) developed VAP. The semi-quantitative culture had 100% sensitivity, 58.2% specificity, 38.9% positive predictive value and 100% negative predictive value. Quantitative EA culture had 88.1% sensitivity, 84.2% specificity, 59.7% positive predictive value and 96.4% negative predictive value. The Receiver operating characteristic (ROC) curve of quantitative EA cultures showed an area under the curve of 0.861 ± 0.034.

Conclusion

The semi-quantitative EA culture had a good negative predictive value and therefore it may be useful for excluding VAP. The quantitative EA culture with a good sensitivity, specificity, positive and negative predictive values can be considered as an acceptable tool for diagnosis of VAP. In addition, the quantitative EA cultures can also guide the selection of appropriate antibiotics for treatment of VAP cases.