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Procalcitonin (PCT)

Infectious Diseases · also called PCT

What it measures

Measures a calcitonin precursor that rises sharply in systemic bacterial infection but only slightly in viral illness. It supports sepsis diagnosis and antibiotic stewardship.

Specimen and preparation

Specimen: Serum or plasma
Tube: Gold top

Reference range

Group	Range
Healthy adult	< 0.05 ng/mL
Low risk of sepsis	< 0.5 ng/mL
Systemic infection likely	≥ 2 ng/mL

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Bacterial sepsis and septic shock
Severe bacterial pneumonia
Major trauma, surgery or burns (non-infective)
Medullary thyroid carcinoma

Method

ECLIA/CLIA or immunofluorescence

Good to know

A fall of 80% from peak or a value below 0.5 ng/mL supports stopping antibiotics.

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