Procalcitonin Increase Identifies Critically Ill Patients at High Risk of Mortality

Sepsis is a major cause of mortality in the Intensive Care Unit (ICU). Efforts have been made to reduce the time needed to diagnose sepsis in order to reduce mortality from sepsis-related multi-organ dysfunction .

Markers of inflammation such as C-reactive protein (CRP) and White Blood Cell count (WBC) have proved far from ideal in identifying critically ill patients who need antimicrobial therapy, because the sensitivity and specificity for bacterial infection is low.

Procalcitonin (PCT) is a 13 kDa 116 amino acid polypeptide, initially described as a prohormone of Calcitonin, a hormone of the calcium metabolism produced in the medullary C-cells of the Thyroid gland5-7. However, recent studies demonstrated that the variant PCT associated with infection can be produced by other tissues.

As kinetic studies on baboons and humans have shown a rapid release within 2-4 hours after injection of bacteria or bacterial toxins, PCT is a substance which is released more rapidly than CRP. The plasma half-life of PCT is close to 24 hours. Measurements of PCT in healthy individuals have shown very low serum levels (<0.05 ng/ml).

In 1993, Assicot et al. reported that elevated levels of serum procalcitonin were closely related to the onset of bacterial infection and seemingly correlated to severity of infection.