Patient Test Information

Procalcitonin

Also known as:

PCT

Formal name:

Procalcitonin

Related tests:

C-Reactive Protein, Complete Blood Count, Blood Culture, CSF Analysis

Why Get Tested?

To help diagnose sepsis if you are critically ill; to help determine the risk of severe sepsis leading to septic shock; to distinguish bacterial from non-bacterial infections

When to Get Tested?

When you are seriously ill and your health care provider wants to distinguish between sepsis and other causes of the illness; sometimes at intervals to monitor effectiveness of antimicrobial treatment

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

How is it used?

The procalcitonin test is relatively new, but its utilization is increasing. Recent studies have shown that it has promise in helping to evaluate the risk that a seriously ill person is developing a systemic bacterial infection. It has primarily been studied in people who present to Emergency Departments or who are admitted to intensive care units (ICUs) and who have symptoms that may be due to sepsis. The procalcitonin test has been approved by the U.S. Food and Drug Administration (FDA) for use in conjunction with other laboratory findings and clinical assessments to assist in the risk assessment of critically ill people for progression to severe sepsis and septic shock. For diagnostic purposes, it is best used during the first day of presentation. It may be used later on to monitor the response to treatment.

Procalcitonin may sometimes be ordered, along with other tests such as a C-reactive protein (CRP), Blood Culture, complete blood count (CBC), or cerebrospinal fluid (CSF) analysis to help detect or rule out sepsis, distinguish between viral and bacterial meningitis, or detect/rule out bacterial pneumonia in those who are seriously ill and in children with a fever of unknown origin.

It may sometimes be ordered when a person has tissue damage due to events such as trauma or surgery or a viral illness such as pneumonia in order to detect the development of a secondary bacterial infection.

Occasionally, a procalcitonin test may be ordered at intervals to monitor the effectiveness of antimicrobial treatment.

When is it ordered?

The procalcitonin test may be ordered along with other tests when a seriously ill person has symptoms that suggest that the person may have a systemic or severe bacterial infection. When used, it is typically ordered as an early detection tool, within the first day of hospital admission.

Complications of sepsis may include:

  • Chills, fever
  • Nausea
  • Rapid breathing, rapid heartbeat
  • Confusion
  • Decreased urine output

More severe symptoms include inflammation throughout the body and formation of many tiny blood clots in the smallest blood vessels. One or more organs may begin to stop working (multi-organ failure, MOF) and there may be a dangerous drop in blood pressure.

Sometimes, procalcitonin may be ordered at intervals to monitor antimicrobial therapy in persons suspected of having sepsis. It may occasionally be ordered when someone has tissue damage from trauma, surgery, or a burn, or a viral illness such a pneumonia and a health practitioner suspects that the person may have developed a secondary infection.

What does the test result mean?

Low levels of procalcitonin in a seriously ill person represent a low risk of sepsis and progression to severe sepsis and/or septic shock but do not exclude it. Low concentrations may indicate a localized infection that has not yet become systemic or a systemic infection that is less than six hours old. It may also indicate that the person's symptoms are likely due to another cause, such as transplant rejection, a viral infection, or trauma - post-surgery or otherwise.

High levels indicate a high probability of sepsis, that is, a higher likelihood of a bacterial cause for the symptoms. They also suggest a higher risk of progression to severe sepsis and then to septic shock.

Moderate elevations may be due to a non-infectious condition or due to an early infection and, along with other findings, should be reviewed carefully. Decreasing procalcitonin levels in a person being treated for a severe bacterial infection indicate a response to therapy.

Very high levels of procalcitonin can be seen with medullary thyroid cancer, but the test is not used to diagnose or monitor this condition.

Is there anything else I should know?

The procalcitonin test is not considered a replacement for the performance of other laboratory tests. Rather, it provides additional information that may allow appropriate treatment to be initiated sooner.

Early detection of systemic bacterial infections, including bacterial pneumonia and bacterial meningitis, is important because they can be life-threatening and can be readily treated. However, the inappropriate use of antibiotics in cases where the illness is not bacterial in origin may cause delays in proper treatment and can encourage the development of antibiotic-resistant organisms.

The procalcitonin test is being studied in additional populations, expanding beyond critically ill ICU patients. As more data are gathered, its clinical usefulness will be better understood and its intended use(s) more fully defined.

What is being tested?

Procalcitonin is a precursor to the thyroid hormone calcitonin. It is normally produced by special cells in the thyroid gland called C-cells and is present in low levels in the blood. However, it may also be made by other cells in the body when stimulated by an intense stressor, in particular systemic bacterial infection (sepsis; as opposed to local bacterial infections). Other stressors include tissue damage due to events such as trauma, surgery, pancreatitis, burns, cardiogenic shock (related to a heart attack), acute organ transplant rejection, and kidney involvement in urinary tract infections in children.

This test measures the amount of procalcitonin in the blood. Levels of procalcitonin in the blood increase rapidly and significantly when a person has sepsis. They are typically only mildly to moderately elevated when a person has a viral infection, a localized infection, or other illnesses as noted above, which may present with some of the same symptoms as sepsis. This gives the procalcitonin test the potential to be used to help detect the presence of a severe bacterial infection in its early stages and to distinguish between a bacterial infection and other causes of symptoms in a seriously ill person.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

  1. Should a procalcitonin test be performed every time a person is seriously ill?

    No, it is generally only indicated when someone is seriously ill and the health practitioner suspects that the person may have sepsis or a severe bacterial infection.

  2. Can a procalcitonin test be performed instead of a blood culture for sepsis?

    No, they give the health practitioner different information. An elevated procalcitonin test may suggest that a person likely has sepsis, but it cannot tell which organism is causing the infection. A blood culture can provide this information and give further guidance on appropriate treatment.

  3. Will an elevated procalcitonin also elevate my calcitonin level?

    No. In most cases, when the procalcitonin is increased, calcitonin levels will be normal. Since they are measured for different purposes, these tests will not typically be performed together.

  4. Can a procalcitonin test be done in my doctor's office?

    In general, no. Procalcitonin is typically performed in a hospital setting and laboratory.