Procalcitonin Levels in Acute Respiratory Infection.

Procalcitonin (PCT) is a biomarker of inflammation that is used to help make clinical decisions, like starting antibiotics or admitting a patient to the hospital. While PCT levels have been widely studied in pneumonia, levels in less severe acute respiratory infections (ARI) have not been well studied. To measure PCT levels in otherwise healthy adults during ARI, we followed 99 healthy adults during the cold and flu season, collecting blood specimens for PCT testing at baseline, and when participants presented with ARI. Ninety-six percent of the ARI samples had PCT levels <0.05 ng/mL. The remaining 4% were <0.25 ng/mL. These data suggest that PCT is not a useful test in ARI of mild-to-moderate severity.