What is this test?
Free PSA measures the unbound portion of prostate-specific antigen. It is used along with a total PSA, not as a separate test.
Why might it be ordered?
- For further evaluation of total PSA in an area where the cause of the elevation is not clear.
- To calculate percent free PSA as part of an individualized assessment for follow-up testing.
What sample is needed?
A healthcare professional collects a venous blood sample. Depending on the method, the laboratory uses serum or plasma.
How should you prepare?
Report any urinary infection, recent prostate procedure and prostate medicines. Follow the laboratory guidance about waiting after ejaculation, cycling or prostate manipulation. Tell the laboratory about all medicines, hormone treatments, vitamins and supplements you take. Do not stop or change treatment unless your clinician tells you to. Follow any instructions about fasting and the time of collection.
How should you understand the result?
The percentage of free PSA is calculated relative to the total PSA. Its importance depends on the total value, age, examination and individual risk. A trend across consecutive measurements made with a comparable method is often more informative than a single value.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.