For many years, VAP was diagnosed by clinical criteria such as fever, leukocytosis and purulent tracheobronchial secretions supported by the radiological evidence of new or persistent pulmonary infiltrates (7). However these criteria are non-specific (8). Studies have shown that clinical criteria have imperfect diagnostic reliability in ventilated patients, and therefore, additional procedures such as cultures of the lower respiratory tract are required for the accurate diagnosis and treatment of VAP (9, 10). However, clinical criteria do remain crucial for defining those patients who may require respiratory sampling (1).