Procalcitonin (PCT)


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Subject: Procalcitonin (PCT)

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  • Procalcitonin (PCT) is a protein that can act as a hormone and a cytokine. It can be produced by several types of cells and many organs in response to proinflammatory stimuli, particularly bacterial infection. It is released under the stimulation of sepsis. PCT levels rise within 6 to 12 hours of bacterial infection with septic consequences.

  • Procalcitonin (PCT) measurement is indicated:

    • On admission to the intensive care unit (ICU) in patients with a known or suspected respiratory infection, or sepsis with a probable bacterial source.

    • In patients in the ICU with a suspicion of a new or relapsed respiratory infection or sepsis.

    • On days 3 and 5 of a course of antimicrobial therapy being given to treat a respiratory infection, or potential sepsis for which a source has not been identified, to aid in assessing response to therapy and in clinical decisions of continuing versus discontinuing antimicrobial therapy.

  • Normal range:

    • Negative: <0.10 ng/mL


  • Diagnosis of bacteremia and septicemia in adults and children (including neonates)

  • Diagnosis, risk stratification, and monitoring of septic shock

  • Differential diagnosis of bacterial versus viral meningitis

  • Differential diagnosis of community-acquired bacterial versus viral pneumonia

  • Monitoring of therapeutic response to antibacterial therapy


  • Procalcitonin levels above 2.00 ng/mL on the first day of ICU admission represent a high risk for progression to severe sepsis and/or septic shock.

  • PCT for initiation of antimicrobial therapy

    • PCT result <0.50 μg/L—initiation of antimicrobial therapy may not be indicated. Consider a noninfectious cause of the clinical syndrome. If antibiotics are withheld, may want to repeat PCT level in 6 hours to rule out an increase that would suggest antibiotic therapy is warranted

    • PCT result 0.50–1 μg/L—initiation of antimicrobial therapy encouraged

    • PCT result >1 μg/L—initiation of antimicrobial therapy strongly encouraged


  • Procalcitonin levels in the serum are elevated in a variety of inflammatory conditions, including bacterial infection, malaria, burns, pancreatitis, and traumatic injury.

  • Levels rise within 2–4 hours, peak generally in the 2nd day, and fall rapidly during recovery.

  • Procalcitonin levels are generally not as high in fungal or viral infection.