What is the clinical significance of procalcitonin (PCT)?

From the Guidelines

Procalcitonin should be used to support the discontinuation of empiric antibiotics in patients who initially appeared to have sepsis, but subsequently have limited clinical evidence of infection, as suggested by the most recent guidelines 1.

Key Points

• Procalcitonin is a biomarker that helps distinguish bacterial infections from other inflammatory conditions, with normal levels typically below 0.05-0.1 ng/mL 1.
• Serial measurements of procalcitonin are more valuable than single readings, with declining levels suggesting resolution of bacterial infection 1.
• Procalcitonin can be used to support shortening the duration of antimicrobial therapy in sepsis patients, with levels of less than 0.5 µg/L or a decrease of greater than or equal to 80% from peak levels guiding antibiotic discontinuation once patients stabilize 1.
• The use of procalcitonin-guided antibiotic treatment in ICU patients with infection and sepsis has been shown to result in improved survival and lower antibiotic treatment duration, as demonstrated by a meta-analysis of 11 RCTs involving 4,482 patients 1.

Clinical Application

• Procalcitonin should be used in conjunction with clinical judgment and other diagnostic information to guide antibiotic therapy decisions, particularly in respiratory infections and sepsis 1.
• The test should not be used to replace clinical judgment, but rather to provide supportive and complementary information to clinical assessment 1.
• Measuring procalcitonin in critically ill patients with a new fever and no clear focus of infection with low to intermediate clinical probability of bacterial infection is recommended, but not in patients with high clinical probability of bacterial infection 1.

Limitations

• The diagnostic accuracy and specificity of procalcitonin are higher than those of C-reactive protein (CRP), but the test is not perfect and should be interpreted in the context of clinical findings 1.
• Procalcitonin levels can be elevated in certain conditions like trauma, surgery, and some cancers, independently of infection 1.
• The use of procalcitonin-guided antibiotic treatment may be limited by the availability of the test and the need for serial measurements 1.

From the Research

Procalcitonin Guidance in Sepsis

• Procalcitonin guidance has been shown to reduce antibiotic duration in patients with suspected or confirmed sepsis, with a weighted mean difference of -1.49 days compared to controls 2.
• The use of procalcitonin guidance has no adverse impact on mortality, with a risk ratio of 0.90, and length of ICU stay, with a weighted mean difference of -0.84 days 2.

Procalcitonin and Sepsis Severity

• Procalcitonin values have been found to have a weak positive correlation with the Sequential Organ Failure Assessment (SOFA) score, indicating a relationship between procalcitonin levels and illness severity 3.
• Higher procalcitonin values have been observed in patients who died compared to those who survived to discharge, although this difference was not statistically significant 3.
• Procalcitonin values have also been found to be higher in patients with bacteremia and gram-negative bacterial infections compared to non-bacteremic and gram-positive bacterial infections 3.

Procalcitonin and Antibiotic Therapy

• Procalcitonin has been compared to C-reactive protein for guiding antibiotic therapy in sepsis, with results showing that C-reactive protein was as useful as procalcitonin in reducing antibiotic use 4.
• The use of procalcitonin to guide antibiotic decision making has been found to result in a reduction in antibiotic use and antibiotic side-effects, which translates into improved survival of patients with respiratory infections and sepsis 5.
• Monitoring of repeated procalcitonin measurements over time has been found helpful for estimating recovery from bacterial infection and prognosis in higher risk situations, such as pneumonia or sepsis 5.

Procalcitonin and Patient Outcomes

• A delta positive procalcitonin has been found to be associated with increased ICU length of stay, although there was no statistical significance in expiration based on antibiotic change in relationship to delta positive change in procalcitonin 6.
• Procalcitonin guidance has been found to have no observed adverse effects on patient outcomes, including mortality and length of ICU stay 2.