Procalcitonin in respiratory disease: use as a biomarker for diagnosis and guiding antibiotic therapy

Procalcitonin (PCT) is a peptide measurable in serum which becomes elevated in response to bacterial infection. Multiple trials have explored the safety and efficacy of using PCT as a biomarker to guide decisions about starting or stopping antibiotic therapy in a wide variety of situations, and PCT assays have recently been approved by the Federal Drug Administration (FDA) in the US for use in both sepsis and respiratory tract infections. While there have been a number of promising results particularly in acute respiratory tract infections and intensive care unit settings, problems including adherence to protocol, cost of the assay and improved antimicrobial stewardship more generally, have limited more widespread adoption. This educational article summarises the evidence for the use of procalcitonin as a biomarker of bacterial infection across the spectrum of respiratory disease and reviews how the use of procalcitonin-guided antibiotic therapy is reflected in current major international guidelines.