Numerous studies have evaluated the diagnostic performance of invasive procedures, or of biochemical and molecular markers in blood or bronchoalveolar lavage (BAL) in patients with ventilator-associated pneumonia (VAP), hospital acquired pneumonia (HAP) and community acquired pneumonia (CAP). These methods are difficult to apply to daily clinical practice and none has proved to be predictive of outcome [5] [6] [7] [8] . Furthermore, many aspects in the strategies for diagnosing HAP and VAP especially regarding the importance of invasive procedures are still controversial [9, 10] . Indeed, a recent study revealed that use of invasive procedures for etiological diagnosis of pneumonia varies considerably between European ICUs [11] . This uncertainty is most likely responsible for antibiotic overtreatment observed in this group of patients [12, 13] . Thus, measures to aid the early identification of patients with pneumonia are underdeveloped. Such measures are needed as patients with pneumonia are at high risk of death and would benefit from early adaption of therapy.