To reflect clinical decision making in real-life situations, sub-analyses were performed. Cases without detection of bacteria (i.e. patients with viral etiology or with no pathogen) were evaluated as clinically bacterial if they fulfilled one of the following criteria: unilobar or multilobar pulmonary infiltrate on CT or CXR; C-reactive protein (CRP) >100 mg/l; procalcitonin (PCT) >0.25 μg/l; antibiotic therapy before rtPCR and with indeterminate biomarkers (CRP >100 mg/l and PCT ≤0.25 μg/l or CRP 51–100 mg/l and PCT not available). These criteria were adapted from earlier publications [17, 21] regarding the diagnosis of bacterial lower RTI.