What is a procalcitonin test?

A procalcitonin test measures the level of procalcitonin in your blood. Normally, you have very low levels of procalcitonin in your blood. But if you have a serious bacterial infection, the cells in many parts of your body will release procalcitonin into your bloodstream. A high level of procalcitonin in your blood may be a sign of a serious infection or sepsis (an overactive and extreme response to infection).

Sepsis (also called septicemia) is your immune system's extreme response to an infection, usually from bacteria. Sepsis happens when an infection you already have spreads into your bloodstream and triggers a chain reaction throughout your body. It causes inflammation (swelling) and blood clots. Without quick treatment, sepsis can rapidly lead to tissue damage, organ failure, or even death.

Infections that lead to sepsis most often start in your lungs, urinary tract, skin, or digestive system. A procalcitonin test can help your health care provider diagnose if you have sepsis from a bacterial infection or if you have a high risk of developing sepsis. This may help you get the right treatment quickly before your condition worsens.

Other names: PCT test

What is it 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. For example, a procalcitonin test can help tell the difference between bacterial and viral pneumonia. This matters because antibiotics help most bacterial infections, but not viral infections.

A procalcitonin test may be used to help:

• Diagnose or rule out a bacterial infection and/or sepsis
• Find out how serious a sepsis infection may be
• Make treatment decisions (such as the need for antibiotics)
• Monitor how well treatment is working
• Diagnose kidney infections in children with urinary tract infections

This test is usually used for very sick people admitted to the hospital.

Why do I need a procalcitonin test?

You may need this test if you have symptoms of sepsis or a serious bacterial infection that could become sepsis. Symptoms of sepsis include:

• Fever or chills
• Clammy or sweaty skin
• Confusion
• Extreme pain
• Rapid heartbeat
• Shortness of breath, feeling like you can't get enough air
• Low blood pressure
• Reduced amounts of urine (pee)

Sepsis is a medical emergency. If you or your loved one has an infection that's not getting better or is getting worse, get medical help right away.

What happens during a procalcitonin test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparation for a procalcitonin test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

High procalcitonin levels mean that you:

• Most likely have sepsis
• May have a high risk of developing severe sepsis and septic shock, a life-threatening condition when your organs don't get enough blood to work properly
• May have a serious systemic bacterial infection that increases your risk for sepsis

The higher your procalcitonin levels, the higher your risk for sepsis and septic shock.

Moderate to mildly high levels of procalcitonin may be sign of:

• The earlier stages of a systemic bacterial infection
• Kidney infection, in children only
• Conditions other than infections, such as tissue damage from trauma, serious burns, recent surgery, severe heart attack

Slightly high levels of procalcitonin mean that you are unlikely to develop sepsis, but they may be a sign of:

• A local bacterial infection, such as a urinary tract infection
• An infection from another cause, such as a virus
• A systemic bacterial infection that is just beginning

If you are being treated for a bacterial infection, decreasing or low procalcitonin levels mean that your treatment is working.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a procalcitonin test?

A procalcitonin test won't show what type of bacteria is causing an infection. To make a full diagnosis, your provider will likely order other tests. But a procalcitonin test does give you important information about your risk for sepsis, so you can start treatment sooner, if needed, and avoid more serious illness.