Using procalcitonin to decrease antibiotic therapy

This topic will discuss Using procalcitonin to guide antibiotic therapy...
Abdelwahab Ward, BS Pharm, PharmD

BACKGROUND ã…¡ Procalcitonin (Normal LEVEL < 0.1 ng/mL [infants > 72 hours – adults]) is a propeptide of calcitonin and is produced in the thyroid gland. All procalcitonin in the thyroid is converted to calcitonin; therefore, serum levels are undetectable or very low in healthy individuals (0.05 ng/mL). In bacterial infections, procalcitonin levels are significantly elevated and can increase to higher than 100 ng/mL.

          What about using procalcitonin levels to shorten antibiotic courses? Procalcitonin levels increase during bacterial infections, but NOT viral. So it's useful to help identify patients who may benefit from antibiotics. Procalcitonin can also help you determine when to stop antibiotics since levels drop quickly as bacterial infections resolve. Don't order procalcitonin if it's a send-out lab that has more than a 24-hour turnaround time. It'll come back too late to be useful. 

LOWER RESPIRATORY TRACT INFECTION (pneumonia, COPD exacerbation, bronchitis) ã…¡ Excellent evidence supports the use of procalcitonin for assisting clinicians in antibiotic management in lower respiratory infections including pneumonia, exacerbations of chronic bronchitis, and other assorted lower respiratory tract infections (bronchitis, asthma exacerbation, etc.). A meta-analysis of 8 studies with 3431 patients found the use of procalcitonin in lower respiratory infection resulted in a 31% decrease in antibiotic prescriptions and a decrease in antibiotic duration of 1.3 days. 

  • Suspected lower respiratory tract infection
    • 0.1 – 0.25 ng/mL: low likelihood for bacterial infection ã…¡ antibiotics discouraged. 
    • > 0.25 ng/mL: increased likelihood bacterial infection ã…¡ antibiotics encouraged. 

Recommended use: based upon this evidence it is suggested that patients considered at risk for bacterial lower respiratory tract infections or being started on antibiotics have a procalcitonin value measure on admission and every 2-3 days subsequently. Interpretation of values is listed in Algorithms 1 and 2.

But be aware of limitations. For example, conditions such as trauma can falsely elevate levels and initial levels can be falsely low since they take up to 24 hours to peak.

          Don't rely solely on procalcitonin for diagnosis or treatment duration. Use it as an additional tool to help guide clinical decisions. If your hospital uses procalcitonin, check a level during initial workup and every one to three days if patients are started on antibiotics. Expect guidance on how to respond to procalcitonin levels to vary by infection since critically ill patients tend to have higher values. For example, when working up a patient in the emergency department (ED) with community-acquired pneumonia, consider starting antibiotics if the procalcitonin is 0.25 ng/mL or higher and then stopping antibiotics when the level trends below 0.25 ng/mL or drops by 80%. 

SEPSIS (Procalcitonin Value) ã…¡ Procalcitonin levels of > 2.0 µg/L predicts sepsis and levels of > 10 µg/L indicate likely septic shock. Sensitivity and specificity of procalcitonin for the diagnosis of sepsis has varied based upon population and underlying diseases. Higher procalcitonin levels have been shown to be associated with a worse prognosis. Use a similar approach for determining whether to stop antibiotics in a patient with sepsis but with a higher cutoff value of 0.5 ng/mL. 

  • Suspected sepsis
    Strongly consider initiating antibiotics in all unstable patients.
    • 0.1 – 0.5 ng/mL:     low likelihood for sepsis ã…¡ antibiotics discouraged.
    • > 0.5 ng/mL: increased likelihood sepsis ã…¡ antibiotics encouraged.
    • > 2.0 ng/mL: high risk of sepsis/septic shock ã…¡ antibiotics strongly encouraged. 

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Abdelwahab Ward, BS Pharm, PharmD