CRP and susceptibility to pneumonia measurement: The FCBI-index value was increased (≥ 1.0) in 97% (95% CI: 93-100%) of the patients with bacterial pneumonia and in 87% (95% CI: 79-100%) of the patients with pneumonia with unknown etiology, while the corresponding percentages were 93% (95% CI: 87-99%) and 79% (95% CI: 70-100%) for CRP, and 79% (95% CI: 70-100%) and 44% (95% CI: 32-56%) for PCT, respectively.