What is the clinical significance of procalcitonin (PCT) levels?

From the Guidelines

Procalcitonin is a valuable biomarker for guiding antibiotic therapy decisions, particularly in respiratory infections and sepsis, with levels above 0.5 ng/mL suggesting possible bacterial infection and levels exceeding 2.0 ng/mL strongly indicating bacterial sepsis, as supported by the most recent and highest quality study 1.

Key Points

• Procalcitonin levels can be used to support shortening the duration of antimicrobial therapy in sepsis patients, as suggested by the Surviving Sepsis Campaign guidelines 1.
• The use of procalcitonin to guide therapy has been associated with a reduced risk of mortality and a reduction in antibiotic exposure, as demonstrated by a meta-analysis of 11 RCTs involving 4,482 patients 1.
• Procalcitonin rises rapidly within 2-4 hours of bacterial infection and decreases rapidly after antibiotic treatment, making it a useful marker for monitoring response to therapy 1.
• Normal procalcitonin levels are typically below 0.05 ng/mL, and values above 0.25-0.5 ng/mL may indicate the need for antibiotic therapy, while levels below 0.25 ng/mL or a decrease of 80% from peak may indicate the need to discontinue antibiotics 1.

Clinical Considerations

• Procalcitonin should be used in conjunction with clinical assessment and other diagnostic tools to guide antibiotic therapy decisions, as recommended by the Society of Critical Care Medicine and the Infectious Diseases Society of America guidelines 1.
• The diagnostic accuracy of procalcitonin is higher than that of C-reactive protein, with a sensitivity and specificity of 0.80 and 0.77, respectively, as demonstrated by a systematic review and meta-analysis 1.
• Procalcitonin may be elevated in severe viral illnesses, such as influenza and COVID-19, which may limit its usefulness in distinguishing between bacterial and viral infections 1.

Recommendations

• Use procalcitonin levels to guide antibiotic therapy decisions in patients with respiratory infections and sepsis, particularly in critically ill patients, as supported by the most recent and highest quality study 1.
• Consider initiating antibiotics for procalcitonin values above 0.25-0.5 ng/mL and discontinuing when levels fall below 0.25 ng/mL or decrease by 80% from peak.
• Use procalcitonin in conjunction with clinical assessment and other diagnostic tools to guide antibiotic therapy decisions.

From the Research

Procalcitonin Overview

• Procalcitonin (PCT) is a host-response biomarker that has shown clinical value for assessing the likelihood of bacterial infections and guiding antibiotic treatment 2, 3, 4, 5, 6
• PCT can help differentiate bacterial from non-bacterial infections and inflammation states, particularly in respiratory illness 2, 3, 4

Clinical Applications of Procalcitonin

• PCT-guided antibiotic stewardship reduces antibiotic exposure and associated side-effects among patients with respiratory infection and sepsis 2, 3, 5
• Low PCT levels can help rule out bacterial infection in patients with low pretest probability for bacterial infection and low-risk general condition 2, 5
• PCT levels can be used to monitor the resolution of infection and guide decisions regarding early termination of antibiotic treatment 2, 5

Limitations and Future Directions

• PCT should not be viewed as a traditional diagnostic marker, and its use should be combined with careful patient assessment, evidence-based clinical algorithms, and continuous notification and regular feedback from all antibiotic stewardship stakeholders 2, 6
• Further studies are needed to better understand the application of PCT in the diagnosis of sepsis, differentiating between microbial and non-microbial infection cases, and determining the therapeutic approaches for sepsis 4, 5
• Optimal strategies for implementation of PCT-guided antibiotic therapy in hospitals, its real-world impact on clinical outcomes and costs, and its applicability to immunocompromised patients need to be examined in future research 5, 6