Using a Procalcitonin Blood Test to Diagnose Sepsis (2024)

A procalcitonin test measures the risk of developing a potentially deadly bacterial infection called sepsis. Sepsis occurs when the body overreacts to a bacterial infection by releasing chemicals that can cause damaging inflammation. If your blood contains an abnormally high level of procalcitonin, a substance your body produces in response to a bacterial infection, it can indicate that you have sepsis or are likely to develop sepsis.

This article explains how the procalcitonin test works, how the results are interpreted, and what the test can and cannot tell you.

What Is a Procalcitonin Test?

The procalcitonin test only requires a simple blood draw. It measures the amount of a substance called procalcitonin produced by many types of cells in the body. Procalcitonin levels can increase significantly when there is a bacterial infection or some form of tissue injury.

When a bacterial infection becomes systemic, meaning that it spreads throughout the body, procalcitonin levels can shoot up dramatically. The higher the level, the greater the likelihood of sepsis.

Other conditions can also increase procalcitonin but usually only to mild to moderate levels. Having elevated procalcitonin does not necessarily mean you have sepsis. It is simply an indication of a systemic infection that needs further investigation.

Other tests will be used to confirm the diagnosis. These may include blood cultures, a complete blood count (CBC), urinalysis, liver or kidney function tests, and imaging tests like ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI).

Difference Between Sepsis and Septicemia

When Is a Procalcitonin Test Used?

The procalcitonin test is ordered when there is a suspicion of sepsis. It is frequently used in emergency rooms or intensive care units when people show signs of sepsis, including high fever, difficulty breathing, low blood pressure, and confusion.

The test is important because sepsis can be difficult to diagnose and doesn't always cause symptoms in the early stages. It is possible, for example, for procalcitonin levels to be low in the very early stages and increase steeply over hours or days.

On the other hand, it is possible to have high procalcitonin levels and no clear symptoms in the early stages. It is only when the extreme inflammation begins to affect organs that severe symptoms will appear.

By testing procalcitonin levels early, doctors can prescribe treatment before the condition becomes serious or life-threatening.

Warning Signs of Sepsis

Sepsis occurs when your body has an extreme reaction to an infection that results in life-threatening inflammation. Symptoms include confusion or disorientation, shortness of breath, rapid heart beat, fever, feeling cold, pain, or clammy skin.

How Bacteremia Leads to Sepsis or Septic Shock

Who Is at Risk of Sepsis?

More than 1.7 million adults in the U.S. develop sepsis every year, according to the Centers for Disease Control and Prevention (CDC). While anyone who gets an infection can develop sepsis, certain groups have a higher chance of getting it because they are more susceptible to infections. They include:

  • People older than 65
  • Children younger than 1
  • People with chronic conditions such as diabetes, cancer, and lung or kidney disease
  • People with weakened immune systems
  • People who recently had a severe illness
  • Pregnant people
  • People who previously had sepsis

What Do the Test Results Mean?

The procalcitonin test cannot diagnose infections. It can show your doctor if sepsis may be occurring, how severe it may be, and whether it is likely to progress to septic shock, which occurs when blood pressure drops dangerously low.

Although the results of a procalcitonin test should be interpreted by a doctor, they are generally described as follows:

  • Normal: 0 to 0.05 micrograms per liter (µg/L)
  • Low risk of sepsis: less than 0.5 µg/L
  • Possible sepsis: between 0.5 µg/L and 2 µg/L
  • Moderate to high risk of sepsis: between 2 µg/L and 10 µg/L
  • Severe sepsis: 10 µg/L or greater

The test can also help determine what type of infection a person has. Most sepsis cases are caused by bacterial infections, but viral or fungal infections can also cause sepsis. Infections that cause sepsis can occur anywhere in the body, including the lungs, skin, or urinary tract.

If the symptoms are severe but the procalcitonin level is low, the cause is more likely viral.Higher procalcitonin levels indicate that the infection is probably bacterial. Knowing what type of infection you have can help ensure that the appropriate treatment is given and that if you have a virus, you aren't needlessly prescribed antibiotics.

A moderate to mildly high level of procalcitonin may also be due to something aside from an infection, such as tissue injury or a chronic condition that causes an elevation in procalcitonin.

Studies have shown that high procalcitonin levels in people with sepsis are associated with a greater risk of septic shock and death.

What Causes High Procalcitonin?

While elevated procalcitonin levels can be a strong indication of sepsis, even minor infections like a tooth abscess can cause procalcitonin levels to rise. Even so, high levels usually point to sepsis.

When procalcitonin levels are low to moderate, sepsis may be a possible cause. But other causes may be to blame. These include conditions that cause severe tissue injury, such as:

  • Severe trauma
  • Burns
  • Surgery
  • Pancreatitis (inflammation of the pancreas)
  • Cardiogenic shock (related to a heart attack)
  • Organ transplant rejection
  • Solid tumor infections (including certain cancers)

People who have certain conditions, such as COPD or chronic kidney disease, may also have elevated baseline levels of procalcitonin.

Risk of Sepsis in Older Adults

Summary

A procalcitonin test is a type of blood test that can help diagnose sepsis and determine a person's risk of severe illness, shock, and death. Because sepsis worsens rapidly, an early diagnosis can ensure that the right medications are prescribed before the condition turns severe.

Based on how high or low the procalcitonin levels are, doctors can also get a better idea as to whether the cause is an infection or another condition. The test can also help differentiate between a bacterial and viral infection or a systemic or local infection.

A Word From Verywell

A procalcitonin level on its own only predicts a likelihood that an infection is present. The procalcitonin result is a guide, not a diagnosis.

People do not receive treatment based on a procalcitonin level alone. A battery of tests is needed, and the treatment is based on an interpretation of the results and the clinical judgment of the physician.

The true value of the procalcitonin level is that it can lead to the early treatment of sepsis. Treating the infection even a few hours earlier can make the difference between an illness that responds to antibiotics and one that lands you in intensive care.

8 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. AlRawahi, A. N., AlHinai, F. A., Doig, C. J., Ball, C. G., Dixon, E., Xiao, Z., & Kirkpatrick, A. W. (2019). The prognostic value of serum procalcitonin measurements in critically injured patients: A systematic review. Critical Care, 23(1). https://doi.org/10.1186/s13054-019-2669-1

  2. MedlinePlus. Procalcitonin test.

  3. Samsudin I, Vasikaran SD. Clinical utility and measurement of procalcitonin. Clin Biochem Rev. 2017;38(2):59-68.

  4. National Institute of General Medical Sciences. Sepsis.

  5. Centers for Disease Control and Prevention. CDC urges early recognition, prompt treatment of sepsis.

  6. Centers for Disease Control and Prevention. About sepsis.

  7. UpToDate. Procalcitonin use in lower respiratory tract infections.

  8. Pandey S, Garg R, Kant S, Verma A, Gaur P. Serum procalcitonin levels in chronic obstructive pulmonary disease patients in North Indian Population.Ann Afr Med. 2019;18(2):103-107. doi:10.4103/aam.aam_44_18

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.

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Using a Procalcitonin Blood Test to Diagnose Sepsis (2024)

FAQs

Is procalcitonin used to diagnose sepsis? ›

PCT, the precursor of the hormone calcitonin, has been used as a biomarker to aid in diagnosis of bacterial infection or sepsis, as well as in differentiating bacterial pneumonia from viral pneumonia and chronic obstructive pulmonary disease (COPD).

Which lab test is the best for diagnosing sepsis? ›

A laboratory workup, including CBC, chemistry panel, LFTs, and biomarkers such as blood lactate, is essential for diagnosis, risk stratification, and prognosis of sepsis. The SOFA score is used to define sepsis and has diagnostic and prognostic value.

What is a procalcitonin blood test used for? ›

A procalcitonin test is mostly used if you are seriously ill and your provider thinks you may have a systemic infection (an infection that affects your entire body). The test helps find out whether bacteria or a virus is causing your infection.

How do you confirm sepsis diagnosis? ›

How is sepsis diagnosed? A single diagnostic test for sepsis does not yet exist, and so doctors and healthcare professionals use a combination of tests and immediate and worrisome clinical signs, which include the following: The presence of an infection. Very low blood pressure and high heart rate.

What is the blood marker for sepsis? ›

PCT and CRP are both proteins produced in response to infection and/or inflammation. They are probably the two most widely used clinical tests to diagnose and manage patients with sepsis, with the exception of lactate. CRP is a well-established biomarker of infection and inflammation29.

When to use procalcitonin? ›

High procalcitonin levels suggest a bacterial infection, whereas low levels suggest a viral infection or noninfectious cause. “The procalcitonin is useful to determine if antibiotics are needed at all: The patient has a fever and is coughing.

What organ shuts down first with sepsis? ›

Organ failure, including kidney failure, is a hallmark of sepsis. As the body is overwhelmed, its organs begin to shut down, causing even more problems. The kidneys are often among the first to be affected.

Can you have sepsis for days without knowing? ›

Sepsis can develop quickly from initial infection and progress to septic shock in as little as 12 to 24 hours.1 You may have an infection that's not improving or you could even be sick without realizing it.

What is the best screening tool for sepsis? ›

NEWS-2 tool most predictive

The National Early Warning Score (NEWS-2) accurately predicted 72.2% of sepsis cases, followed by the Modified Early Warning Score (MEWS; 46.8%), the Systemic Inflammatory Response Syndrome (SIRS; 30.4%), and the quick Sequential Organ Failure Assessment (qSOFA; 24.0%).

How reliable is procalcitonin? ›

Among patients presenting to the hospital who received blood cultures and a procalcitonin test, we found that the sensitivity of procalcitonin at a commonly used cutoff of 0.5 ng/mL to detect a BSI was low at 68%, indicating that procalcitonin is a weak rule-out test for BSI at admission.

Is procalcitonin a good marker for infection? ›

Overall, PCT levels provide a promising laboratory measurement for identifying bacterial infections. However, the utility of this test is limited by the clinical setting and patient population.

What are the limitations of procalcitonin? ›

What are the limitations of procalcitonin? False positive and false negative results can occur with any test and clinical context should guide interpretation of PCT results.

What are the two criteria needed for a sepsis diagnosis? ›

Sepsis should be suspected in patients meeting at least two of the three qSOFA criteria: respiratory rate of 22 breaths per minute or greater, altered mental status, and systolic blood pressure of 100 mm Hg or less.

What lab test is most critical in diagnosing sepsis? ›

Peripheral blood cultures are useful for investigating the infectious etiology of sepsis and for managing appropriate antimicrobial treatment. Other tests, including CBC and chemistries, provide a baseline to assess therapeutic response.

What is the best indicator of sepsis? ›

A high level of lactic acid caused by infection can be an important clue that you have sepsis. C-reactive protein (CRP): Your body produces C-reactive protein is produced when there is inflammation. Several conditions can cause inflammation, including infections.

What is procalcitonin intended for? ›

Indications for serum procalcitonin measurement include the following: To aid in the diagnosis and risk stratification of bacterial sepsis. To aid in the diagnosis of renal involvement in children with urinary tract infection. To aid in distinguishing bacterial from viral infections, including meningitis.

Is PCT a biomarker for sepsis? ›

Procalcitonin is regarded as a biomarker with both diagnostic and prognostic impact, offering Emergency Departments and Intensive Care clinicians a key tool to aid in the diagnosis of sepsis, and thereby improve antibiotic decision-making and potentially improve clinical outcomes [1]

What is the difference between procalcitonin and CRP? ›

PCT levels are raised much earlier during an infectious process in comparison with CRP (4–12 hours vs 24–38 hours), which facilitates earlier diagnosis. PCT can be used as a prognostic marker as its levels correlate with bacterial load and severity of infection, which is not the case for CRP.

What is the cut off value for procalcitonin in sepsis patients? ›

The optimum cutoff value for procalcitonin is approximately 0·5 ng/mL and the optimum cutoff value for C-reactive protein is approximately 15 mg/L.

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