Procalcitonin is a precursor of the hormone calcitonin, normally produced in small amounts.

During systemic bacterial infections and sepsis, procalcitonin levels rise significantly.

Clinical uses include:

Detecting severe bacterial infections and differentiating them from viral infections.

Monitoring sepsis progression and severity.

Guiding antibiotic therapy (start, duration, and discontinuation).

Supporting diagnosis in patients with fever of unknown origin.

The test is performed using a blood sample.

Analyte: Procalcitonin concentration in blood serum.

Normal Range: < 0.1 ng/mL (varies slightly by lab).

Elevated Levels:

0.1–0.5 ng/mL: Possible local bacterial infection.

> 0.5 ng/mL: Suggests systemic bacterial infection or sepsis.

> 2 ng/mL: Strongly indicates severe sepsis or septic shock.

Clinical Use:

Differentiates bacterial vs viral infections.

Monitors infection severity and treatment response.

Helps reduce unnecessary antibiotic use.