Procalcitonin as a Marker of Etiology in Adults Hospitalized With Community-Acquired Pneumonia

Background. Recent trials suggest procalcitonin-based guidelines can reduce antibiotic use for respiratory infections. However, the accuracy of procalcitonin to discriminate between viral and bacterial pneumonia requires further dissection. Methods. We evaluated the association between serum procalcitonin concentration at hospital admission with pathogens detected in a multicenter prospective surveillance study of adults hospitalized with community-acquired pneumonia. Systematic pathogen testing included cultures, serology, urine antigen tests, and molecular detection. Accuracy of procalcitonin to discriminate between viral and bacterial pathogens was calculated. Results. Among 1735 patients, pathogens were identified in 645 (37%), including 169 (10%) with typical bacteria, 67 (4%) with atypical bacteria, and 409 (24%) with viruses only. Median procalcitonin concentration was lower with viral pathogens (0.09 ng/mL; interquartile range [IQR],