Additional Information

Patients with untreated end-stage renal failure may have PCT levels >0.5 ng/mL in the absence of sepsis, but levels should fall to normal within 3 hemodialysis treatments. ESRD patients on stable dialysis treatments have levels similar to those of patients with normal renal function. Patients with medullary thyroid carcinoma or more rarely islet cell tumors may have mild to moderate elevations in absence of sepsis, but levels >2.0 ng/mL are rare. As with any laboratory test, correlation must be made with clinical information.

Procalcitonin (PCT) is a 116 amino acid precursor peptide of calcitonin. Expression of this group of peptides in healthy humans is limited to thyroid C-cells and to a lesser extent, other neuroendocrine cells in the lung, adrenal glands and gastrointestinal tract.  Normal circulating levels are below the detection limit of this assay.  During severe systemic inflammation, in particular as seen in bacterial infection, the tissue specific control of PCT production and processing breaks down.  Non-infectious inflammation can result in stimulation of other inflammatory markers such as cytokines, interleukins, and C-reactive protein, but needs to be extremely severe to cause PCT elevations.  PCT elevations are detectable with 2-4 hours after the triggering event and peak by 12-24 hours.  PCT secretion parallels closely with disease severity and levels decline with resolution of illness.   

Unless there is an ongoing stimulus, PCT has a half-life of 24-36 hours and is produced in neutropenic patients as well.  PCT is more specific for bacterial infections and may be used to monitor the effectiveness of anti-microbial therapy.

PCT is useful for:

• Diagnosis of bacteremia and septicemia in adults, children (including neonates and neurtropenic patients) A PCT of >2.0 ng/mL predicts sepsis and >10 ng/mL indicates likely septic shock. The higher the PCT level, the worse the prognosis. With successful treatment, PCT levels usually fall with a half-life of 24 to 36 hours.
• This test is also useful for diagnosis of renal involvement in urinary traction infection in children. A PCT level of >0.5 ng/mL has 70% to 90% sensitivity and 80% to 90% specificity for renal involvement.
• This test is also useful for diagnosis of risk stratification and monitoring of septic shock
• Diagnosis of systemic secondary infection post-surgery, severe trauma, burns, and multiorgan failure
• Differential diagnosis of bacterial versus viral meningitis
• Monitoring therapeutic response to antibacterial therapy