PCT Blood Test

What is Procalcitonin?

Procalcitonin is a precursor peptide for the hormone calcitonin, whose function is to partake in calcium homeostasis. In normal circumstances, procalcitonin concentrations in blood are low. But when there is a systemic bacterial infection, procalcitonin concentration shoots up, and hence it is a valuable biomarker for the detection of such infections.

Purpose of the Procalcitonin Test

The PCT test serves mainly to contribute to the diagnosis of bacterial infection and to estimate the severity of bacterial infection. It is useful in the following:

• The diagnosis of Sepsis: Sepsis is a critical reaction to an infection that results in tissue injury, organ failure, and mortality. High PCT levels indicate the occurrence of sepsis, which facilitates timely treatment.
• Discriminating Between Bacterial and Viral Infections: As procalcitonin concentration increases in bacterial infections but not in viral infections, the test aids in planning the correct management.
• Directing Antibiotic Treatment: Through observing PCT concentration, clinicians are able to decide on initiating or terminating antibiotic treatment, ensuring appropriate use of antibiotics.

When should the Test be Performed?

The PCT test should be performed in certain clinical situations such as:

• Those with signs of systemic infection, including fever, tachycardia, tachypnea, and confusion.
• Those suspected of having lower respiratory infections, such as pneumonia.
• Those with suspected sepsis or septic shock.
• Monitoring the efficacy of antibiotic treatment in those with established bacterial infections.

Test Procedure

The PCT test is a quick blood test:

• Preparation: No special preparation is required.
• Collection of sample: A medical practitioner will take a blood sample from a vein, usually in the arm.
• Testing: The blood sample is tested in a laboratory to quantify procalcitonin.
• Outcome: Results are typically ready within 2-3 days, depending on the processing time of the laboratory.

Interpretation of the outcome

Procalcitonin is quantified in nanograms per milliliter (ng/mL). Interpretation of the test results is as follows:

• < 0.1 ng/mL: Within normal range; infection by bacteria is unlikely.
•  0.1 - 0.25 ng/mL: Low risk for bacterial infection; consider alternative explanations.
•  0.25 - 0.5 ng/mL: High risk; bacterial infection is likely.
•  > 0.5 ng/mL: High risk; bacterial infection is very likely.

Note that a high PCT level can also be seen in non-infectious illness, such as major trauma, surgery, or burns. Results should thus be considered in light of the patient's entire clinical presentation.

Tests Suggested in Addition

Based on the clinical presentation, other tests may be indicated in addition to the PCT test for an overall evaluation:

• Complete Blood Count (CBC): Assesses the general health and identifies a range of disorders, including infections.
• C-Reactive Protein (CRP): Assesses the CRP level, another inflammatory marker in the body.
• Blood Cultures: Determine the offending bacteria involved in the infection.
• Chest X-ray or CT Scan: Helpful in the diagnosis of pneumonia or other respiratory infections.

These tests, when combined with the PCT test, assist in creating a whole picture of the patient's condition and direct appropriate treatment plans.

Advantages of the Procalcitonin Test

• Early Identification: Facilitates the timely detection of severe bacterial infections.
• Directed Treatment: Assists in making decisions to start or stop antibiotic therapy.
• Tracking Progress: Serial PCT levels can track the progress of treatment and the course of the disease.
• Antibiotic Stewardship: Curbs inappropriate antibiotic utilization, fighting antibiotic resistance.

The Procalcitonin blood test is a useful diagnostic test to identify serious bacterial infections and aid treatment decisions. Through the use of PCT levels, doctors can distinguish between viral and bacterial infections, gauge the severity of an infection, and track the response of the infection to treatment. At MaxAtHome, we strive to make our diagnostic services accessible and accurate, so you can get the best care in the convenience of your own home.