What is being tested?
Procalcitonin is a substance produced by many types of cells in the body, often in response to bacterial infections but also in response to tissue injury. The level of procalcitonin in the blood can increase significantly in systemic bacterial infections and sepsis. This test measures the level of procalcitonin in the blood.
Sepsis is the body’s serious, overwhelming and sometimes life-threatening inflammatory response to a bacterial infection. Normally, a person’s immune system targets an infection, confining the bacteria and limiting its response to the infected area. However, some infections may begin in one site of the body and then spread to the blood (bacteremia) and possibly to other sites. With sepsis, the body produces a generalized inflammatory response to the infection. This can cause a significant rise or fall in body temperature, increased heart rate and breathing rate, and a decrease in blood pressure. If not treated successfully, sepsis can progress to severe sepsis.
Other conditions can also increase procalcitonin in the blood, but usually procalcitonin is only mildly to moderately elevated. Examples of these conditions 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.
The procalcitonin test is useful in helping to detect sepsis and severe bacterial infections in the early stages and to distinguish between a bacterial infection and other non-bacterial causes of signs and symptoms in a seriously ill person.
How is it used?
The procalcitonin test may be used, along with other tests and examinations, to help detect or rule out sepsis in a seriously ill person. It has primarily been used in people who seek care at emergency departments or who are admitted to intensive care units (ICUs) with signs and symptoms that may be due to sepsis.
The procalcitonin test may be used to help:
- Determine the risk that a critically ill person will progress to severe sepsis and septic shock, or the risk of the person dying
- Distinguish between bacterial and non-bacterial causes of infections, such as meningitis and pneumonia
- Diagnose kidney infections in children with urinary tract infections
- Detect the development of a secondary bacterial infection in a person who has tissue damage due to trauma or surgery, or a viral illness such as pneumonia
- Guide antibiotic treatment and/or monitor effectiveness—the test may be used in helping to decide whether antibiotics should be started or stopped for patients with lower respiratory infections and whether antibiotics can be discontinued in patients with sepsis
Examples of other tests that may be used along with procalcitonin include C-reactive protein (CRP), cultures (e.g., blood culture, urine culture), lactate, blood gases, complete blood count (CBC), and cerebrospinal fluid (CSF) analysis.
When is it ordered?
The procalcitonin test may be ordered when a seriously ill person has signs and symptoms that suggest a systemic or severe bacterial infection and/or sepsis. Signs and symptoms of sepsis may include:
- Chills, shivering, fever
- Clammy or sweaty skin
- Extreme pain or discomfort
- Rapid breathing
- Rapid heartbeat
- Confusion or disorientation
- Less frequent urination
The test may be ordered when a person has an infection, like pneumonia or meningitis, and it is not known whether the cause is bacterial or non-bacterial. Sometimes the test may be ordered when a child has signs and symptoms that suggest a urinary tract infection.
A series of procalcitonin tests may be ordered at intervals when a healthcare practitioner wants to monitor antibiotic treatment and/or decide whether treatment can be safely discontinued.
The test may occasionally be ordered when someone has tissue damage from trauma, surgery, or a burn, or a viral illness such a pneumonia and a healthcare practitioner suspects that the person may have developed a secondary bacterial infection.
What does the test result mean?
Procalcitonin results are interpreted in conjunction with findings from clinical evaluations as well as other laboratory tests.
Low levels of procalcitonin in a seriously ill person may indicate a low risk of developing sepsis and progression to severe sepsis and/or septic shock but do not exclude it.
Low levels may indicate that the person’s symptoms are due to a cause other than a bacterial infection, such as a viral infection. A low level may also indicate a localized infection that has not spread or become systemic, or a systemic infection that is less than six hours old.
High levels indicate a high probability of sepsis and also suggest a higher risk of progression to severe sepsis and septic shock. High levels may also been seen in people with serious bacterial infections, such as meningitis.
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. They may also be seen in children with kidney infections.
Decreasing procalcitonin levels over time in a person being treated for sepsis or a bacterial infection indicate a response to therapy. Stable or increasing procalcitonin levels may indicate the need for continued therapy.
Is there anything else I should know?
Very high levels of procalcitonin can be seen with medullary thyroid cancer, but the test is not used to diagnose or monitor this condition.
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 or discontinued 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 use of antibiotics in non-bacterial conditions may cause delays in proper treatment and can lead to more antibiotic-resistant bacteria.
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.
Who is at risk of sepsis?
Sepsis is more common in newborns, infants, and in the elderly, but other people at risk include post-surgery patients, people with internal medical devices such as catheters, people with chronic conditions such as diabetes, and people with weakened immune systems. Though less common, even healthy children and adults can develop sepsis from an infection that can progress if not recognized early and treated.
What types of infections can lead to sepsis?
Infections that most commonly lead to sepsis include those of the lung (pneumonia), urinary tract, skin, and digestive tract. Common bacteria that can trigger sepsis include Staphylococcus aureus, Escherichia coli (E. coli), and some types of Streptococcus.
What other tests may be done if a systemic bacterial infection or sepsis is suspected?
How long will it take for results?
This depends on the laboratory performing the testing. Procalcitonin testing is often done in serious and emergency cases, so results may be available within an hour or so.
Elsewhere On The Web
MedlinePlus Medical Encyclopedia: Sepsis
MedlinePlus Medical Encyclopedia: Septic shock
American Lung Association: Pneumonia
Centers for Disease Control and Prevention: Sepsis
National Institute of General Medical Sciences: Sepsis Fact Sheet