Procalcitonin (PCT) has developed into a promising new biomarker for early detection of (systemic) bacterial infections. PCT is a 116-amino acid residue that was first explained by Le Moullec et al. in 1984; however, its diagnostic significance was not recognized until 1993. In 1993, Assicot et al. demonstrated a positive correlation between high serum levels of PCT and patients with positive findings for bacterial infection and sepsis (eg, positive blood cultures). PCT assays with a specificity of 79%, is utilized to more accurately determine if a bacterial species is the cause of a patient’s systemic inflammatory reaction.
Procalcitonin serum levels have been shown to increase 6 to 12 hours following initial bacterial infections and increase steadily 2 to 4 hours following the onset of sepsis. The half-life of PCT is between 20 to 24 hours; therefore, when a proper host immune response and antibiotic therapy are in place, PCT levels decrease accordingly by 50% over 24 hours.
PCT
serum levels can become elevated among patients during times of noninfectious
conditions, such as with trauma, burns, carcinomas (medullary C-cell, small
cell lung, & bronchial carcinoid), immunomodulator therapy that increase
proinflammatory cytokines, cardiogenic shock, first 2 days of a neonate's life,
during peritoneal dialysis treatment, and in cirrhotic patients (Child-Pugh
Class C). Furthermore, PCT levels have found to be falsely elevated in patients
suffering from various degrees of chronic kidney disease which can, in turn,
alter baseline results making the determination of an underlying bacterial
infection difficult to establish.
