Not medically reviewed
Inflammation
Procalcitonin (PCT)
Not medically reviewed · Content last updated · 1 min read ·
This is the date the draft was written, not a medical review date.
The precursor of calcitonin, released from many tissues during systemic bacterial infection. It rises within 3 to 6 hours and, with a half-life of about 24 hours, is used to support diagnosis of bacterial sepsis and to guide antibiotic duration.
Reference interval
| Conventional (ng/mL) | SI (µg/L) | |
|---|---|---|
| Adults | < 0.1 (upper limit) ng/mL | < 0.1 (upper limit) µg/L |
Specimen: Serum or plasma (EDTA or heparin) · Conventional × 1 = SI
Causes of high values
Systemic bacterial infection and sepsis (higher values with severity), bacterial pneumonia and meningitis. Non-infective causes include major trauma, surgery, burns, cardiogenic shock, severe pancreatitis, medullary thyroid carcinoma, neonates in the first 48 hours, and renal failure.
Causes of low values
A low value makes systemic bacterial infection less likely, although localised infection, early infection (first hours) and some intracellular organisms may not raise it. Viral infections and inflammatory diseases usually produce small rises.
Pre-analytical and method notes
Typical interpretive bands are below 0.1 ng/mL (bacterial infection unlikely), about 0.25 to 0.5 ng/mL (possible), and above 2 ng/mL (high likelihood of systemic bacterial infection or sepsis), but these thresholds vary by assay and guideline. It should support, not replace, clinical judgement, and sequential values are more informative than a single result. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
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