From the Guidelines
Procalcitonin levels above 0.5 ng/mL generally suggest bacterial infection that may benefit from antibiotic therapy, while levels above 2.0 ng/mL strongly indicate severe bacterial infection requiring immediate antibiotic treatment. For lower respiratory tract infections, a threshold of 0.25 ng/mL is often used, with levels below 0.1 ng/mL suggesting antibiotics can likely be withheld 1. However, procalcitonin should not be the sole determinant for antibiotic therapy. Clinical assessment remains paramount, and antibiotics should be initiated based on the overall clinical picture, including symptoms, vital signs, and other laboratory findings. Some key points to consider when using procalcitonin levels to guide antibiotic therapy include:
- Procalcitonin levels can help distinguish between bacterial and viral infections, as they rise in response to bacterial endotoxins and inflammatory cytokines 1
- A procalcitonin level of less than 0.25 ng/mL may indicate a low likelihood of bacterial infection, and antibiotics can likely be withheld 1
- Procalcitonin levels can 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 1
- Serial procalcitonin measurement can be useful in monitoring the response to antibiotic therapy and guiding de-escalation or discontinuation of antibiotics 1 It's essential to note that procalcitonin levels should be interpreted in the context of the overall clinical picture, and antibiotics should not be withheld or discontinued solely based on procalcitonin levels without considering other clinical factors. The most recent and highest quality study 1 suggests that procalcitonin levels can be a useful tool in guiding antibiotic therapy, but should be used in conjunction with clinical assessment and other laboratory findings.
From the Research
Procalcitonin Levels and Antibiotic Treatment
- The decision to initiate or discontinue antibiotic therapy can be guided by procalcitonin (PCT) levels, with various studies suggesting different cutoff values 2, 3, 4.
- For stable, low-risk patients with respiratory infections, PCT levels of <0.25 µg/L can guide the decision to withhold antibiotics or stop therapy early 2.
- In critically ill patients with suspected sepsis, clinicians should not initially withhold antibiotics, but PCT levels of <0.5 µg/L or levels that decrease by ≥80% from peak can guide discontinuation once patients stabilize 2, 3, 4.
- A cutoff value of 0.25 μg/L in non-ICU patients or of 0.5 μg/L in ICU patients seems appropriate for making a decision about the initiation and discontinuation of antibiotic therapy 3.
- In patients with a significantly elevated baseline PCT level, a subsequent drop of >80% appears to be reasonable for discontinuing antibiotics 3, 4.
Clinical Scenarios and PCT Levels
- For adult patients suspected of community-acquired lower respiratory tract infection (LRTI), withholding antibiotic therapy is suggested when the serum PCT level is low (<0.25 ng/mL) 4.
- In adults with suspected bacterial meningitis, integrating serum PCT measurements in a clinical decision rule can help distinguish between viral and bacterial meningitis, using a 0.5 ng/mL threshold 4.
- For ICU patients suspected of community-acquired infection, using a threshold serum PCT value to help the decision to initiate antibiotic therapy is not recommended due to insufficient data 4.
- In children, the use of PCT levels to predict bacterial infection has shown limited clinical utility 5, 6.