Also Known As:
PCT

This article was last modified on December 21, 2020

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C-Reactive Protein (CRP)

At a Glance

Why Get Tested?

To help diagnose sepsis if you are critically ill and to help determine your risk of progressing to severe sepsis and septic shock; to help identify serious bacterial infections and to distinguish between bacterial and non-bacterial conditions; to help guide antibiotic treatment

When To Get Tested?

When you are seriously ill and have signs and symptoms of a systemic infection or sepsis; when you have signs and symptoms that may be due to a bacterial infection and your healthcare practitioner wants to determine whether antibiotics would be effective; at intervals to monitor effectiveness of antibiotic treatment

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

Looking For Test Results?

Looking For Reference Ranges?

You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

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.

Common Questions

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?

Other tests may include cultures (e.g., blood culture, urine culture or cultures of other body fluids), complete blood count (CBC), lactate, blood gases, comprehensive metabolic panel (CMP), prothrombin time (PT) and/or partial thromboplastin time (PTT) and C-reactive protein (CRP).

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.

View Sources

Sources Used in Current Review

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Kaplan, L. (2016 August 16 Updated). Systemic Inflammatory Response Syndrome Workup. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/168943-workup#showall. Accessed on 1/22/17.

Douglas, D. (2016 March 16). Procalcitonin Guidance Curbs Antibiotic Use in Critically Ill. Reuters Health Information. Available online at http://www.medscape.com/viewarticle/860394. Accessed on 1/22/17.

Lin, J. and Yap, S. (2015 November 24 Updated). Procalcitonin. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/2096589-overview. Accessed on 1/22/17.

(2016 September Updated). Sepsis. ARUP Consult. Available online at https://arupconsult.com/content/sepsis. Accessed on 1/22/17.

Cunha, B. (2016 March 18 Updated). Bacterial Sepsis Workup. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/234587-workup#showall. Accessed on 1/22/17.

(February 2015) Sutirtha Chakraborty, MD. Do We Need Procalcitonin for Sepsis? Ask the Expert, Clinical Laboratory News. Available online at https://www.aacc.org/publications/cln/articles/2015/february/procalcitonin-for-sepsis. Accessed February 2017.

Wacker C, et al. Procalcitonin as a diagnostic marker for sepsis: a systematic review and meta-analysis. The Lancet Infectious Diseases. Volume 13, No. 5, p426–435, May 2013. Available online at https://www.ncbi.nlm.nih.gov/pubmed/23375419. Accessed February 2017.

Cabral L, et al. The Use of Procalcitonin (PCT) for Diagnosis of Sepsis in Burn Patients: A Meta-Analysis. PLoS One. 2016; 11(12): e0168475. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5179235/. Accessed February 2017.

Sources Used in Previous Reviews

Yealy, D. et. al. (2009 September 8). Blood Test Narrows Down Need for Antibiotics. MedlinePlus HealthDay News [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/news/fullstory_89106.html. Accessed October 2009.

Brown, A. (2009 June 19). Procalcitonin Testing May Shorten Antibiotic Course in ICU Patients. Medscape Today from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/704569. Accessed October 2009.

Boggs, W. (2009 January 7). Procalcitonin Levels Lower With Blood Stream Infection in Setting of Prior Sepsis. Medscape Today from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/586453. Accessed October 2009.

(2008 December 5). Procalcitonin Discriminates Between Bacterial and Aseptic Meningitis in Children. Medscape Today from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/584813. Accessed October 2009.

Barclay, L. (2009 February 9). Procalcitonin, CRP May Predict Serious Bacterial Infection in Febrile Infants. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/588042. Accessed October 2009.

Barclay, L. (2009 September 16). Procalcitonin Measurements May Reduce Rates of Antibiotic Use for Lower Respiratory Tract Infections. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/708991. Accessed October 2009.

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Procalcitonin