Guidance of antibiotic therapy with procalcitonin in lower respiratory tract infections: insights into the ProHOSP study

In the recently published ProHOSP trial, we investigated the safety and external validity of procalcitonin (PCT) guidance for antibiotic therapy in patients with different severities of lower respiratory tract infections, mainly pneumonia. In this addendum, we aim to extend the initial report by reinforcing the rational of the PCT algorithm and by presenting more detailed data on antibiotic therapy in different severities of infection. In milder, mostly viral respiratory infections (i.e. acute or chronic bronchitis) initial prescription of antibiotics was markedly reduced by PCT guidance because PCT remained low in most patients. In pneumonia, PCT showed a severity-dependent increase and highest levels in patients with positive blood cultures. Thus, the main effect in pneumonia was a severity- and bacteremia-adapted reduction of the duration of antibiotic courses. In lower respiratory tract infections, PCT guidance had a differential effect on antibiotic exposure depending on the underlying type and severity of respiratory tract infection.