PCT significantly increases during severe sepsis and septic shock, making it a valuable marker for determining prognosis and monitoring antibiotic therapy. PCT concentrations increase considerably in patients with septic shock and decrease with successful treatment of septic infection.
As the PCT increases, so does the risk for severe sepsis and septic shock. In healthy individuals, PCT is < 0.05 ng/mL. Moderately elevated levels (up to 2.0 ng/mL) indicate that sepsis is possible, and there is a slight risk of progression to severe sepsis. PCT levels in sepsis are generally greater than 2 ng/mL and often can reach values between 10 and 100 ng/mL in severe sepsis, or considerably higher in septic shock.
PCT has a very high negative-predictive value as a marker of bacterial infection. This makes it a useful marker to help rule out sepsis in emergency department and critical care settings; however, the role of PCT in the discrimination between SIRS and sepsis is still controversial.