From the Guidelines
Procalcitonin is a valuable biomarker for sepsis diagnosis and monitoring, and its levels can guide antibiotic therapy decisions, with levels <0.5 ng/mL suggesting against bacterial sepsis and levels >2 ng/mL strongly suggesting sepsis. Procalcitonin is a precursor protein of the hormone calcitonin that is normally produced by C-cells in the thyroid gland. In healthy individuals, procalcitonin levels are very low (<0.05 ng/mL) because it is immediately converted to calcitonin. However, during bacterial infections, procalcitonin is produced in large quantities by various tissues throughout the body, particularly in response to bacterial endotoxins and inflammatory cytokines. This makes procalcitonin an excellent biomarker for sepsis diagnosis and monitoring.
Key Points
- Procalcitonin levels rise rapidly within 2-4 hours of infection onset, peak at 12-24 hours, and decline when infection resolves.
- For sepsis analysis, procalcitonin offers several advantages: it distinguishes bacterial from viral infections (viral infections typically don't significantly elevate procalcitonin); levels correlate with infection severity (higher levels indicate more severe infections); and it can guide antibiotic therapy decisions.
- Serial measurements can help clinicians determine if antibiotic therapy is effective or if it can be safely discontinued, potentially reducing unnecessary antibiotic use and antimicrobial resistance, as suggested by the Surviving Sepsis Campaign guidelines 1.
- Recent studies have also highlighted the potential of procalcitonin to reduce antibiotic use in patients with COVID-19, with one study finding a more than two-fold reduction in defined daily doses of antibiotic use without any increase in mortality among patients with a procalcitonin level of less than 0.25 ng/ml 1.
- The most recent guidelines from the Society of Critical Care Medicine and the Infectious Diseases Society of America also suggest measuring procalcitonin in addition to bedside clinical evaluation in critically ill patients with a new fever and no clear focus of infection, if the probability of bacterial infection is deemed low to intermediate 1.
From the Research
Pathophysiology of Procalcitonin
- Procalcitonin (PCT) is a biomarker that has gained attention for its role in the diagnosis and management of sepsis 2, 3.
- PCT is a peptide precursor of calcitonin, which is produced by the thyroid gland, but in the context of sepsis, it is produced by various tissues and organs in response to bacterial infections 4.
- The level of PCT in the blood increases in response to bacterial infections, making it a useful marker for distinguishing between bacterial and viral infections 3, 5.
Analysis of Sepsis using Procalcitonin
- PCT has been shown to have good discriminatory properties to differentiate between bacterial and viral inflammations, with rapidly available results 3.
- The use of PCT can help in early risk stratification and provide prognostic information, which can aid in optimizing therapeutic decisions, including antibiotic stewardship 3, 4.
- PCT kinetics over time can improve the monitoring of critically ill patients with sepsis, influencing decisions regarding de-escalation of antibiotics 3, 6.
- Studies have shown that PCT-guided antibiotic treatment can result in improved survival and lower antibiotic treatment duration in ICU patients with infection and sepsis 6.
- Trends in PCT levels over time can be used to individualize the duration of antibiotics without negative impacts on mortality 5.