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Company
Tumor Markers
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Currently under review
Pending specialist review and validation.
This test measures the percentage of prostate specific antigen in your blood that circulates unbound, or free, compared with the portion that is attached to blood proteins. PSA is a protein made by the prostate. By looking at how much of the total PSA is in the free form, clinicians can gain additional insight into the source of the PSA.
Free PSA percentage is calculated from two measurements taken from a single blood sample, total PSA and free PSA. It is commonly ordered together with total PSA as part of prostate health evaluation.
Free PSA percentage helps your clinician assess whether an elevated PSA level is more likely related to benign conditions like prostate enlargement or inflammation, or whether there is a higher chance of prostate cancer. It is often used when total PSA alone does not give a clear picture, helping guide decisions about next steps such as repeating tests, imaging, or biopsy.
This test does not diagnose cancer on its own. Results are interpreted alongside your age, family history, symptoms, digital rectal exam findings, prior PSA results, and imaging when appropriate. Using free PSA percentage can reduce unnecessary biopsies while still identifying people who need closer evaluation.
In general, a higher free PSA percentage is more consistent with benign conditions, while a lower percentage suggests a higher likelihood of cancer. However, there is overlap, and many noncancer factors can influence the result. One result should not be viewed in isolation.
Your clinician will consider the free PSA percentage together with your total PSA, changes over time, and clinical findings. If the result is unexpected, they may repeat the test after avoiding activities or situations that can affect PSA, treat any urinary or prostate infection, or use additional tools such as MRI or referral to a urology specialist to decide on the safest and most appropriate plan.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Both can temporarily raise total PSA, which may change the calculated free PSA percentage. Avoid these activities before testing if your clinician advises.
A digital rectal exam, catheterization, cystoscopy, or a recent prostate biopsy can alter PSA measurements for a period of time. Testing is often scheduled away from such procedures.
Inflammation or infection of the prostate or urinary tract can shift PSA values and the free fraction. Testing is best done after symptoms resolve and treatment is completed.
Drugs like finasteride or dutasteride lower PSA and can change the balance of free and total PSA. Hormone therapies or testosterone use may also influence results. Tell your clinician about all medications and supplements.
Free PSA is cleared from the blood in part by the kidneys. Reduced kidney function can increase free PSA and affect the percentage.
Some immunoassays can be affected by biotin, potentially giving inaccurate PSA or free PSA results. Consider pausing high-dose biotin before testing if your clinician recommends it.
Different labs and assay methods can yield slightly different free PSA percentages. When possible, use the same lab for follow-up testing to improve consistency.
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