From the Guidelines
Procalcitonin (PCT) is a valuable biomarker for guiding antibiotic therapy decisions, particularly in patients with suspected bacterial infections, sepsis, or respiratory infections, with levels above 0.5 ng/mL suggesting possible bacterial infection and levels exceeding 2.0 ng/mL strongly indicating sepsis 1.
Clinical Utility of Procalcitonin
The clinical utility of PCT lies in its ability to distinguish bacterial infections from other causes of inflammation, with PCT levels rising four hours after exposure to bacteria and reaching a maximum level after six to eight hours 1.
- PCT levels are associated with the severity of the infection and decrease rapidly after antibiotic treatment 1.
- Serial measurements of PCT can help monitor treatment response, with declining levels indicating effective therapy 1.
- PCT is particularly valuable for antibiotic stewardship, as low levels can support decisions to withhold antibiotics in ambiguous cases or discontinue them earlier when levels normalize 1.
Comparison with CRP
While C-reactive protein (CRP) is also an acute-phase protein that rises in response to inflammation or infection, PCT has been shown to have higher diagnostic accuracy and specificity for sepsis compared to CRP 1.
- A recent systematic review and meta-analysis found that PCT had an area under the summary receiver operator characteristic (SROC) curve of 0.85, compared to 0.73 for CRP 1.
- However, the literature does not strongly favor one over the other, and the choice between PCT and CRP may depend on individual patient factors and clinical context 1.
Recommendations for Use
PCT levels of less than 0.5 µg/L or levels that decrease by greater than or equal to 80% from peak levels may guide antibiotic discontinuation once patients stabilize 1.
- Measuring PCT or CRP 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 in addition to bedside clinical evaluation, but not in patients with high clinical probability of bacterial infection 1.
- PCT-guided antibiotic treatment in ICU patients with infection and sepsis patients has been shown to result in improved survival and lower antibiotic treatment duration 1.
From the Research
Definition and Clinical Utility of Procalcitonin (PCT)
- Procalcitonin (PCT) is a circulating polypeptide produced in response to bacterial infections 2, 3.
- PCT is widely used to distinguish between sepsis and Systemic Inflammatory Response Syndrome (SIRS), and to guide antibiotic therapy 2, 4.
Diagnostic Accuracy of PCT
- PCT has demonstrated superior diagnostic accuracy for a variety of infections, including sepsis 3.
- A systematic review and meta-analysis found that PCT has a mean sensitivity of 0.77 and specificity of 0.79 for the diagnosis of sepsis in critically ill patients 5.
- The area under the receiver operating characteristic curve was 0.85, indicating that PCT is a helpful biomarker for early diagnosis of sepsis 5.
Clinical Applications of PCT
- PCT can be useful for antimicrobial stewardship and its utilization may safely lead to significant reduction of unnecessary antimicrobial therapy 3, 4.
- PCT-guided antibiotic therapy has been shown to reduce antibiotic exposure and associated side-effects among patients with respiratory infection and sepsis 6.
- PCT can help differentiate bacterial from non-bacterial infections and inflammation states, particularly in respiratory illness 6.
Limitations and Considerations
- PCT is not a universal and perfect biomarker, as it can also be increased in noninfectious disease conditions 3.
- The results of PCT tests must be interpreted carefully in the context of medical history, physical examination, and microbiological assessment 5, 6.
- Patient-specific decisions regarding antibiotic usage are highly complex and require consideration of multiple factors, including clinical situation, acuity and severity of presentation, and PCT test results 6.