Spectrum: Local Antimicrobial Stewardship, for Billings Clinic

What is Procalcitonin (PCT)?

Overview

Procalcitonin is a 116 amino acid precursor of calcitonin which is normally produced in the thyroid.

  • Serum concentrations are normally <0.05 μg/L

Under systemic inflammatory conditions, especially associated with system bacterial infections much larger quantities are produced in many body tissues.

  • Released in response to bacterial toxins and bacteria-specific proinflammatory mediators particularly interleukin 1b, tumor necrosis factor and interleukin 6

Levels are not elevated in pure viral infections.

  • PCT production is blocked by interferon-gamma, a cytokine released in response to viral infection

Detectable within 2-4 hours of infection to peak around 6-24 hours

  • Half-life around 25-30 hours

  • Daily decline is expected in patients with well controlled infections

  • ~50% reduction daily expected when infection is controlled

  • Careful slower decline in renal failure

  • Not impaired by neutropenia or other immunosuppressive states

Proportionally elevated to the severity of the infection

Generally PCT levels <0.1 μg/L generally excludes bacterial infection

  • Reminder: false negative PCT may occur in localized infection