Procalcitonin Test

The procalcitonin test, also known as the PCT test or serum procalcitonin test, measures the amount of procalcitonin in a blood sample. It is mainly used to detect and evaluate bacterial infections that require urgent medical attention, including sepsis (a severe and potentially life-threatening condition that happens when the body has a very strong response to an infection).

Procalcitonin is normally found in very low amounts in the blood. When a bacterial infection occurs, many tissues in the body begin releasing procalcitonin into the bloodstream, causing its levels to rise quickly. This increase is more often associated with bacterial infections and is rarely seen with viral infections.

The test is mainly used for seriously ill patients, especially those in hospitals, when doctors suspect a serious infection affecting the whole body. It helps identify bacterial infections early and understand how severe the condition may be. It also helps doctors differentiate between bacterial infections and other conditions that can cause similar symptoms, such as non-bacterial inflammation.

A doctor may recommend a PCT blood test for people who have symptoms that may suggest a serious bacterial infection or sepsis, such as:

• Fever or chills
• Nausea
• Difficulty breathing/fast breathing
• Rapid heartbeat
• Altered mental state (confusion)
• Reduced urine output
• Sticky or sweaty skin
• Severe pain
• Low blood pressure

The test may also be recommended for:

• People with suspected sepsis
• Hospitalised individuals with severe bacterial infections
• People with respiratory tract infections, including pneumonia
• People receiving antibiotic treatment for a suspected bacterial infection
• Children with urinary tract infections that may involve the kidneys
• People whose doctor needs to determine whether an infection is bacterial or viral

The frequency of procalcitonin testing depends on the clinical condition, the severity of illness, and whether the test is used to assess treatment response.

A procalcitonin test helps identify and monitor conditions associated with bacterial infections and sepsis, including:

• Sepsis (bloodstream infection): Procalcitonin levels increase in sepsis, a life-threatening condition in which the body's response to an infection damages its own tissues and organs.
• Severe bacterial infections: The test helps detect serious bacterial infections affecting different parts of the body.
• Systemic infections: Procalcitonin levels may be high in those with systemic infections that spread throughout the body.
• Bacterial pneumonia and other respiratory tract infections: The test may help differentiate between bacterial respiratory infections and viral infections.
• Kidney infections in children with urinary tract infections (UTIs): Procalcitonin testing may help identify kidney involvement in children with UTIs.
• Monitoring response to antibiotic therapy: Changes in procalcitonin levels can help doctors determine whether antibiotic treatment is working.
• Assessment of infection severity: Higher procalcitonin levels may indicate more severe bacterial infections and assist in making treatment decisions.

What to Expect Before the Procalcitonin Test

No fasting is required for a standalone Procalcitonin test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise procalcitonin levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the Procalcitonin Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

This test measures one important parameter:

• Procalcitonin: Measures the amount of procalcitonin in the blood, which can rise during serious bacterial infections and sepsis.

The procalcitonin test measures the level of procalcitonin in the blood, expressed in nanograms per millilitre (ng/mL). In healthy individuals, procalcitonin levels are usually very low. The procalcitonin normal range is given in the table below:

The procalcitonin test result is interpreted by comparing the procalcitonin level in your blood with the laboratory reference range, as explained in the table below:

The procalcitonin test is a simple and safe blood test. However, like most blood tests, it has some minor risks and limitations.

Possible Risks of the Test

Some people may experience mild pain, slight bleeding, or a small bruise at the site of needle insertion. These effects are usually temporary and resolve on their own within a short time.

Limitations of the Procalcitonin Test

• Procalcitonin levels may increase due to conditions such as recent surgery, severe burns, trauma, or a heart attack, even if there is no bacterial infection.
• Certain medicines that stimulate the immune system may increase procalcitonin levels and affect the test results.
• A low procalcitonin level does not completely rule out a bacterial infection or sepsis.
• The test result should always be interpreted along with symptoms, medical history, and other laboratory findings.

Doctors may advise the following tests along with the procalcitonin test to help identify the source of infection, assess its severity, and monitor recovery:

• Complete blood count (CBC)
• Blood culture test
• Urine test (urinalysis)
• C-reactive protein (CRP) test
• Liver function tests (LFTs)
• Lactate test
• Arterial blood gas (ABG) test