What Is Procalcitonin (PCT)?

What it is

Procalcitonin is a precursor of calcitonin that rises markedly in systemic bacterial infection and sepsis, but much less in viral infection.

Why it matters

PCT helps distinguish bacterial from viral infection and guides antibiotic decisions.

Specimen

Whole blood / serum / plasma

Interpretation

Elevated = supports bacterial infection/sepsis; low = less likely bacterial.

Limitations

Supportive marker — interpret with clinical context; not a standalone diagnosis.

Related test: Procalcitonin Rapid Test — specimen: WB / S / P