Procalcitonin

Procalcitonin is a peptide that serves as a biomarker for bacterial infection and sepsis. It is the precursor of calcitonin, normally produced by the thyroid, but during systemic bacterial infection it is expressed by many tissues throughout the body, leading to elevated blood levels. Procalcitonin levels rise within two to six hours of infection, peak around 24 to 48 hours, and decline as the patient improves or with successful antibiotic therapy. It is measured in serum or plasma by immunoassays.

Clinical use and interpretation

Procalcitonin is used to help distinguish bacterial infections from viral or noninfectious inflammatory states and to guide antibiotic therapy. It can support decisions about initiating antibiotics in certain respiratory infections and can aid in determining the duration of antibiotic treatment in sepsis or post-surgical patients. Cutoff values vary by condition and assay, with higher levels suggesting a bacterial etiology and lower levels reducing the likelihood of bacterial infection. Procalcitonin should be interpreted in the clinical context and not used in isolation.

Limitations and considerations

Procalcitonin may be less reliable in neonates, post-operative patients without infection, severe trauma, pancreatitis, or advanced kidney disease, and it can be influenced by noninfectious inflammation or certain medications. There is inter-assay variability, and no single threshold applies to all settings. Used appropriately, procalcitonin can help reduce unnecessary antibiotic use, but clinical judgment remains essential.

History

Procalcitonin as a biomarker for sepsis gained prominence in the 1990s and has since been incorporated into several clinical pathways and guidelines.