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Procalcitonin: Using PCT Results

Interpretation of Results

Healthy individuals: Determination of normal values with a highly sensitive assay revealed normal values to be below 0.05 ng/mL.17

PCT serum concentrations are elevated in clinically relevant bacterial infections and continue to rise with the increasing severity of the disease. However, as an expression of individually different immune responses and different clinical situations, the same focus of infection may be associated with varying individual elevations in PCT concentrations. Therefore, clinicians should always use PCT results in conjunction with the patient’s other laboratory findings and clinical signs, and interpret the concrete values in the context of the patient’s clinical situation.*

The reference ranges below are provided for orientational purposes only.


Diagnosis of systemic bacterial infection/sepsis 2,3
SIRS, sepsis, severe sepsis, and septic shock are categorized according to the criteria of the consensus conference of the American College of ChestPhysicians/Society of Critical Care Medicine.3

PCT < 0.5 ng/mL
Systemic infection (sepsis) is not likely.

Local bacterial infection is possible.

Low risk for progression to severe systemic infection (severe sepsis).

Caution: PCT levels below 0.5 ng/mL do not exclude an infection, because localized infections (without systemic signs) may be associated with such low levels.

Also if PCT is measured very early after a bacterial challenge (usually < 6 hours), these values may still be low. In this case, PCT should be re-assessed 6-24 hours later.14

PCT ≥ 0.5 and < 2 ng/mL
Systemic infection (sepsis) is possible, but other conditions are known to induce PCT as well.*
Moderate risk for progression to severe systemic infection (severe sepsis). The patient should be closely monitored both clinically and by re-assessing PCT within 6-24 hours.
PCT ≥ 2 and < 10 ng/mL
Systemic infection (sepsis) is likely, unless other causes are known.*
High risk for progression to severe systemic infection (severe sepsis).
PCT ≥ 10 ng/mL
Important systemic inflammatory response, almost exclusively due to severe bacterial sepsis or septic shock.
High likelihood of severe sepsis or septic shock.

Low PCT levels do not automatically exclude the presence of bacterial infection.

Such low levels may be obtained, during the early course of infections, in localized infections and in subacute endocarditis. Therefore, followup and re-evaluation of PCT in clinical suspicion of infection is pivotal. The PCT measuring technique should be chosen according to clinical use.



3. Bone RC, Balk RA, Cerra FB, Dellinger RP, Fein AM, Knaus WA, Schein RM, Sibbald WJ. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Chest 1992; 101: 1644-55.

14. Christ-Crain M, Jaccard-Stolz D, Bingisser R, Gencay MM, Huber PR, Tamm M, Muller B. Effect of
procalcitonin-guided treatment on antibiotic use and outcome in lower respiratory tract infections: cluster randomised,single-blinded intervention trial. Lancet. 2004;363:600-7.

17. Morgenthaler NG, Struck J, Fischer-Schulz C, Seidel-Mueller E, Beier W, Bergmann A. Detection of procalcitonin (PCT) in healthy controls and patients with local infections by a sensitive ILMA. Clin Lab 2002; 48: 263-70.



Watch the inspiring video of sepsis survivor Patricia Cragen and her family as they experience a once in a lifetime event at Strike Out Sepsis Day with the St. Louis Cardinals on August 31, 2015. Watch Video >

See highlights from the Second National Forum on Sepsis, held September 16, 2015 in Washington, DC, and learn more about the Rory Staunton Foundation’s initiatives to raise awareness and knowledge about sepsis. Watch Video >


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