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Procalcitonin

Category Biochemistry
Test background

Intact procalcitonin is secreted in response to inflammatory stimuli including bacterial infections. Procalcitonin increases can be seen 2–4 hours after bacterial induction, rise rapidly and reach a plateau after 6–12 hours. Concentrations then remain high for up to 48 hours and fall if the infection is controlled with a half-life of approximately 24–30 hours.

Clinicial Indications

Procalcitonin concentrations may be helpful in the diagnosis of systemic bacterial infection. Suggested cut-offs for the diagnosis of Systemic Bacterial Infection are given below, taken from the method information sheet and found on https://www.procalcitonin.com

< 0.5Systemic infection (sepsis) is not likely. Local bacterial infection is possible. Low risk for progression to severe systemic infection (severe sepsis). CAUTION: PCT levels < 0.5 μg/L do not exclude an infection, because localized infections (without systemic signs) may be associated with such low levels. Also, if the PCT measurement is done very early after onset of infection (usually < 6 hours), these values may still be low. In this case, PCT levels should be reassessed 6–24 hours later.
≥ 0.5 to < 2Systemic infection (sepsis) is possible, but various conditions are also known to induce PCT. (see Notes below) Moderate risk for progression to severe systemic infection (severe sepsis). The patient should be closely monitored both clinically and by reassessing PCT levels within 6–24 hours.
≥ 2 to < 10Systemic infection (sepsis) is likely, unless other causes are known (see Notes below). High risk for progression to severe systemic infection (severe sepsis).
≥ 10Important systemic inflammatory response, almost exclusively due to severe bacterial sepsis or septic shock. High likelihood of severe sepsis or septic shock.
Reference range

≥ 0.07 ug/L

NB: Procalcitonin increases after birth and remains elevated for 2 – 3 days. See https://www.procalcitonin.com/clinical-utilities/sepsis/reference-values-sepsis.html for more detailed information

Sample & container required Serum preferred. Heparin (green top) can also be accepted
Sample volume min 0.5 mL
Transport storage Serum must be analysed within 8h if kept on cells/separator gel at room temperature. Referral samples should be separated, frozen and transported on dry ice.
Turnaround time 1 day
Notes

Other conditions than systemic bacterial infection may also increase procalcitonin levels including

– Neonates at < 48 hours of life (physiological elevation)
– First days after a major trauma, major surgical intervention, severe burns, or treatment with OKT3 (muromonab-CD3) antibodies and other drugs stimulating the release of proinflammatory cytokines
– Patients with invasive fungal infections
– Patients with acute attacks of Plasmodium falciparum malaria
– Patients with prolonged or severe cardiogenic shock, prolonged severe organ perfusion anomalies, small cell lung cancer, severe liver cirrhosis and acute or chronic viral hepatitis, or medullary C-cell carcinoma of the thyroid

Falsely low procalcitonin levels in the presence of bacterial infection may occur during the early course of infections, in localized infections, and in subacute infectious endocarditis.