Procalcitonin: What is Procalcitonin
PCT is the prohormone of calcitonin (CT). Whereas CT is secreted by the C-cells of the thyroid after hormonal stimulation, PCT can be produced by numerous cell types and organs after proinflammatory stimulation, especially when caused by bacterial challenge.1
In healthy people, plasma PCT concentrations are found to be below 0.05 ng/ml, but can increase up to 1000 ng/ml in patients with severe sepsis or septic shock.
Elevated PCT levels indicate bacterial infection accompanied by a systemic inflammatory reaction.
Localized infections do not generally cause circulating PCT increases. Slightly elevated PCT concentrations are observed in bacterial infections with minor systemic inflammatory response.
Very high values have been observed during acute disease conditions with severe systemic reactions to an infection, in cases of severe sepsis or septic shock.
This biomarker is now being recognized as a useful tool in the diagnostic process.
One major advantage of PCT compared to other parameters is its early and highly specific increase in response to severe systemic bacterial infections and sepsis.2,3 Therefore, in septic conditions, increased PCT levels can be observed 3-6 hours after an infectious challenge. PCT levels are usually low in viral infections, chronic inflammatory disorders or autoimmune processes. PCT levels in sepsis are generally greater than 0.5-2 ng/mL and often reach values between 10 and 100 ng/mL, or considerably higher in individual cases, thereby enabling diagnostic differentiation between these various clinical conditions and a severe bacterial infection (sepsis) (Figure 1).
1.Christ-Crain M, Müller B. Procalcitonin in bacterial infections – hype, hope or more or less? Swiss Med Wkly
2005; 135: 451-60.
2. Harbarth S, Holeckova K, Froidevaux C, Pittet D, Ricou B, Grau GE, Vadas L, Pugin J; Geneva Sepsis Network. Diagnostic value of procalcitonin, interleukin-6, and interleukin-8 in critically ill patients admitted with suspected sepsis. Am J Respir Crit Care Med. 2001; 164: 396-402.
3. Muller B, Becker KL, Schachinger H, Rickenbacher PR, Huber PR, Zimmerli W, Ritz R. Crit Care Med. 2000; 28: 977-83. Calcitonin precursors are reliable markers of sepsis in a medical intensive care unit.