Would you place a patient on antibiotics (abx) for a procalcitonin (Procal) level of 0.16?

From the Guidelines

I would not recommend placing a patient on antibiotics for a procalcitonin level of 0.16 ng/mL alone, as this value falls within a low-risk range that doesn't strongly suggest bacterial infection requiring immediate antibiotic therapy. The decision to start antibiotics should be based on a comprehensive clinical assessment including vital signs, symptoms, physical examination findings, other laboratory results, and the patient's overall clinical picture, as suggested by the most recent guidelines 1. If the patient has clear signs of infection (fever, elevated white blood cell count, specific symptoms) despite the borderline procalcitonin, antibiotics might be warranted. Procalcitonin is a biomarker that helps distinguish bacterial from viral infections, with levels typically rising significantly (>0.5 ng/mL) during bacterial infections, as noted in a study published in 2021 1. A level of 0.16 suggests either no significant bacterial infection or possibly very early infection.

Key Considerations

• The patient's clinical presentation and overall condition should guide the decision to start antibiotics, rather than relying solely on procalcitonin levels.
• A comprehensive clinical assessment should include vital signs, symptoms, physical examination findings, and other laboratory results.
• The most recent guidelines suggest restricting the use of antimicrobial drugs in mild-to-moderately ill patients with COVID-19 infection, especially in those with low, initial PCT levels (<0.25 ng/mL) 1.
• Serial procalcitonin measurement may be useful in monitoring patients and guiding antibiotic therapy, as suggested by a study published in 2023 1.

Next Steps

• Close monitoring with repeat procalcitonin measurement in 6-12 hours would be reasonable before starting antibiotics, unless the patient's condition deteriorates.
• Antibiotics should be considered if the patient's condition worsens or if there are clear signs of bacterial infection, as recommended by the guidelines 1.

From the Research

Procalcitonin Levels and Antibiotic Therapy

• The decision to place a patient on antibiotics (abx) based on a procalcitonin (Procal) level of 0.16 should be guided by clinical evidence and guidelines.
• According to a study published in the American journal of health-system pharmacy 2, 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.
• However, another study published in Clinical chemistry and laboratory medicine 3 suggests that low PCT levels can help rule out bacterial infection in patients with both low pretest probability for bacterial infection and low-risk general condition.
• In this case, a Procal level of 0.16 is below the suggested cutoff value, which may indicate a low likelihood of bacterial infection.

Clinical Considerations

• The clinical situation, including the pretest probability for bacterial infection, acuity, and severity of presentation, should be taken into account when interpreting PCT levels 3.
• Patient-specific decisions regarding antibiotic usage are highly complex and require careful consideration of multiple factors, including PCT test results, clinical symptoms, and risk factors 3, 4.
• The use of PCT-guided therapy has been shown to reduce antibiotic exposure and associated side-effects among patients with respiratory infection and sepsis 2, 3, 4.

Limitations and Variability

• There is high variability in PCT values among patients with suspected bacterial infections, which can limit the usefulness of PCT as a diagnostic tool 5.
• The ability of PCT to predict bacterial infection is only fair, with area under the curve of receiver operating characteristic plots ranging between 0.63 and 0.71 5.
• Therefore, PCT levels should be interpreted in conjunction with clinical symptoms, risk factors, and other diagnostic tests to guide antibiotic therapy.