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Procalcitonin (PCT)

Clinical Biochemistry

Information:

Requesting Information

In the GHNHSFT Critical Care Departments only, PCT is being used to guide discontinuation of antimicrobials as this is where the evidence is strongest.

Please refer to the Procalcitonin (PCT) Testing SOP (A2357) if requesting a test outside of the Department of Critical Care setting.

Background Information

  • Increased PCT levels are found in patients suffering from bacterial sepsis, especially severe sepsis and septic shock. PCT has been proposed as a tool to guide decisions relating to antibiotic requirements.
  • As a biomarker of infection it has many ideal properties including a rapid rise in response to stimulation and a fall in response to control of the infection
  • PCT may be elevated in any condition where a significant systemic inflammatory response is seen, e.g. following major trauma, surgery, burns, pancreatitis.
  • A PCT of < 4ng/ml in patients with acute pancreatitis (within 48h of onset) suggest bacterial infection is unlikely.
  • PCT may be falsely elevated in small cell lung cancer or medullary C-cell carcinoma of the thyroid.

Patient preparation

If patient on high dose biotin therapy (>5mg/day) collect sample at least 8 hours after the last dose

Sample requirements

Requests for procalcitonin always require a fresh sample. The test cannot be added to a sample already in the laboratory because of the risk of carryover.

For adults, 3.5 ml of blood taken into a rust top gel tube.

3.5ml rust top tube



Storage/transport

Send immediately to the laboratory at room temperature. Samples need to be centrifuged within 4 hours.

Required information

Relevant clinical details including reason for the request.

Turnaround times

The assay is are run throughout the day and night, at the GRH Clinical Biochemistry laboratory. The in-lab turnaround time is less than 6 hours. Results are made available as soon as they are technically approved.

Reference ranges

Expected values

Normal range: <0.05ng/mL

Clinical cut-off:

<0.50ng/mL represents a low risk of severe sepsis and/or septic shock

>2.00ng/mL represents a high risk of severe sepsis and/or septic shock

PCT is normally less than 0.05 ng/ml (equivalent to less than 0.05 ug/L) in healthy individuals. note however that normal levels do not exclude infection. All results should be interpreted in the context of the patient's clinical history.

Local treatment guidelines

PCT is not a substitute for good clinical judgement and cannot be used in isolation.

  • PCT <0.5 ng/ml – minimal PCT response. Ongoing infection unlikely therefore witholding antimicrobials strongly advised.
  • If PCT was also measured at the start of treatment a fall by more than 80% from this initial value suggests antimicrobials can also be stopped. If this initial value was <0.5 ng/ml non-bacterial infections or causes of systemic inflammation should be considered.
  • PCT > 0.5 ng/ml to 2.0ng/ml – please discuss with a Microbiology Consultant.
  • PCT >2.0 ng/ml – bacterial infection likely. Treat as appropriate or discuss with Microbiology.

  • If follow-up PCTs fail to fall then this suggests either treatment failure or a new source of infection. Appropriate investigations should be performed (e.g. full septic screen, imaging) and a change in antimicrobial therapy considered.

Further information

To learn more about PCT please visit Lab Tests Online

Page last updated: 09/07/2026 | Page last reviewed: 09/07/2026

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