Procalcitonin test: what the result means (PCT)
What procalcitonin is
Procalcitonin is a protein made by the thyroid gland and by other cells in the body. In a healthy person's blood there is very little of it, but during a severe bacterial infection or sepsis the amount can rise sharply within a few hours. Viral infections, on the other hand, most often do not raise procalcitonin significantly — which is why the test is used to tell a bacterial infection from a viral one and to decide whether treatment against bacteria is needed. According to MedlinePlus, procalcitonin is most often measured in hospital, in order to establish or rule out a bacterial infection and/or sepsis, and also to monitor how a patient is responding to treatment — a falling procalcitonin shows that the treatment is working. Because the result depends on the particular clinical situation and on the laboratory method used, it is always assessed by a doctor together with other tests and symptoms, and not by the patient alone.
A raised procalcitonin
According to MedlinePlus, a high procalcitonin most often points to a bacterial infection and is associated with the risk of sepsis — the higher the value, the greater the risk of severe sepsis and septic shock. A moderately raised procalcitonin may indicate an early systemic bacterial infection or a kidney infection in children, or it may be linked with trauma, burns, surgery or a heart attack without infection. A slightly raised value may mean a local bacterial infection (of the urinary tract, for example) or a viral infection.
| Level of the result | What it may indicate (MedlinePlus) |
|---|---|
| High | Most often a bacterial infection; associated with the risk of sepsis — the higher the value, the greater the risk of severe sepsis and septic shock |
| Moderately raised | May indicate an early systemic bacterial infection or a kidney infection in children; may also be linked with trauma, burns, surgery or a heart attack without infection |
| Slightly raised | May mean a local bacterial infection (of the urinary tract, for example) or a viral infection |
MedlinePlus describes these levels without numeric values and without units, so the interpretation depends on the laboratory method and on the clinical situation, and it is always made by a doctor rather than by the patient.
When the test is done
- When sepsis or a severe bacterial infection is suspected, especially in a patient who is in hospital
- When it needs to be established whether the infection was caused by bacteria or by a virus, before treatment against bacteria is prescribed
- To follow how the body is responding to treatment of a bacterial infection — whether procalcitonin is falling
- When signs of sepsis appear: fever or chills, damp or cold skin, confusion, severe pain, a rapid heartbeat, shortness of breath, low blood pressure, reduced urination
How to prepare
- According to MedlinePlus, no special preparation is needed for the procalcitonin test
- Blood is taken from a vein in the usual way
Is there a normal procalcitonin level?
MedlinePlus does not give a specific numeric reference range with units for procalcitonin — a healthy person's blood contains very little of it, and the interpretation depends on the laboratory method and on the clinical situation. The exact interval on the result sheet, and what it means, is always explained by a doctor.
Possible causes of a raised result
- A severe bacterial infection or sepsis — the higher the value, the greater the risk
- An early systemic bacterial infection
- A local bacterial infection, for example a urinary tract infection
- Non-infectious causes: trauma, burns, surgery, a heart attack
- A kidney infection in children
Possible symptoms
- Fever or chills
- Damp or cold, clammy skin
- Confusion
- Severe pain
- A rapid heartbeat
- Shortness of breath
- Low blood pressure
- Reduced urination
What to discuss with a doctor
- Whether there are other signs of sepsis or of a bacterial infection — a doctor assesses them together with the clinical condition
- Other markers of inflammation (CRP, white blood cells), so that the picture is clearer
- Repeating the test over time — a falling procalcitonin shows that the treatment is working
- A possible search for the source of the infection (the urinary tract or the lungs, for example)
A low or falling procalcitonin
According to MedlinePlus, a low or falling procalcitonin usually means that there is no significant bacterial infection, or that the treatment being given for a bacterial infection is working. Because a healthy person's blood contains very little procalcitonin, a low result is most often considered normal rather than a deviation that needs a separate explanation.
Possible reasons for a low result
- There is no significant bacterial infection or sepsis
- Successful treatment of a bacterial infection — the value falls in response to treatment
- An early stage of infection, when procalcitonin has not yet had time to rise
What to discuss with a doctor when the result is low
- If symptoms persist despite a low procalcitonin, the doctor may consider other causes or other tests
- Repeating the test over time, to confirm that the treatment is effective
- Other markers of inflammation and infection, for the overall picture
Full site in Lithuanian: proactiva.app
Frequently asked questions
›What is the normal procalcitonin level?
MedlinePlus does not give a specific numeric reference range with units — a healthy person's blood contains very little procalcitonin, and the interpretation depends on the laboratory method and on the clinical situation. The exact interval on your result sheet, and what it means, is always explained by a doctor.
›How does procalcitonin differ from CRP?
Both are markers of inflammation, but procalcitonin is more specific to bacterial infection and sepsis — it rises sharply during a bacterial infection and reacts little to a viral one. CRP rises in inflammation of many different kinds, so it is less precise at telling a bacterial infection from a viral one.
›Why is procalcitonin most often measured in hospital?
According to MedlinePlus, the test is used mainly in hospitalised patients, to establish or rule out a severe bacterial infection or sepsis and to decide about treatment against bacteria, so in outpatient practice it is ordered less often than CRP.
›Do I need to prepare for the test in any special way?
No. According to MedlinePlus, no special preparation is needed for the procalcitonin test — blood is taken from a vein in the usual way.
›What does a falling procalcitonin during treatment mean?
A procalcitonin that falls during treatment of a bacterial infection usually shows that the treatment is working. That is why the test is sometimes repeated over a few days to assess how treatment is going — the decision about further treatment is always made by a doctor.
›Does a high procalcitonin always mean sepsis?
Not always. According to MedlinePlus, a very high value is most often associated with sepsis, but a moderate rise can also be caused by non-infectious reasons, for example trauma, burns, surgery or a heart attack, so the result is discussed by a doctor together with other tests.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.