Purpose

Sepsis is a daily challenge in the hospital setting. Today, various therapeutic strategies are known to improve survival in patients with sepsis. Early assessment is important for determination of the appropriate treatment. 

PCT is the prohormone of the hormone calcitonin, but PCT and calcitonin are distinct proteins. Calcitonin is exclusively produced by C‑cells of the thyroid gland in response to hormonal stimuli, whereas PCT can be produced by several cell types and many organs in response to pro-inflammatory stimuli, in particular by bacterial products.1 

In healthy people, plasma PCT concentrations are found to be below 0.1 ng/mL.2 Depending on the clinical background, a PCT concentration above 0.1 ng/mL can indicate clinically relevant bacterial infection, requiring antibiotic treatment.3 PCT levels rise rapidly (within 6‑12 hours) after a bacterial infectious insult with systemic consequences. The magnitude of the increase in PCT concentration correlates with the severity of the bacterial infection.4 At a PCT concentration > 0.5 ng/mL, a patient should be considered at risk of developing severe sepsis or septic shock.5,6 On the other hand, the relief of the septic infection is accompanied by a decrease in the PCT concentration which returns to normal with a half-life of 24 hours,7,8 i.e., the continuous decline of PCT is indicative of effective source control measures and has been implicated in the safe de-escalation of antibiotic therapy.9,10 

By evaluating PCT concentrations, the physician may use the findings to aid in the risk assessment of critically ill patients for progression to severe sepsis and septic shock. In addition, the change of PCT levels over time offers information about the risk of mortality after diagnosis of severe sepsis or septic shock.

_{Source: Roche cobas Elecsys BRAHMS PCT method sheet, V 4.0 2024-10}