PSA, Free and Total (with Percent Free PSA) Panel
The PSA, Free and Total panel measures total and free prostate-specific antigen and derives the percent free PSA to improve the specificity of PSA testing. It is most useful for refining an intermediate total PSA (roughly 4–10 ng/mL), where a lower percent free PSA favours cancer and a higher percentage favours benign disease, helping inform biopsy decisions.
3
Biomarkers
Blood (serum)
Sample
1–3 business days
Turnaround
No — however, the sample should be taken before, or appropriately after, ejaculation, digital rectal examination, or prostatic instrumentation, which transiently raise PSA
Fasting
What is the PSA Free + Total test?
The PSA, Free and Total Panel measures total PSA and free PSA and derives the percent free PSA, improving the specificity of PSA testing in the detection of prostate cancer. It is used chiefly to refine the interpretation of an intermediate total PSA, where the decision about whether to proceed to biopsy is most uncertain. Within the prostate assessment pathway, total PSA is the first-line marker but is non-specific, particularly in the intermediate range of roughly 4–10 ng/mL where benign prostatic hyperplasia and cancer overlap. Adding free PSA to calculate the percent free PSA helps discriminate between these: a lower percentage points toward malignancy and a higher percentage toward benign disease. The panel thus reduces unnecessary biopsies while helping identify men who should proceed to further evaluation such as MRI and biopsy. It is interpreted alongside age-specific thresholds, the digital rectal examination, PSA density and velocity, and the clinical picture, and specimen handling matters because free PSA is labile.
What does the PSA Free + Total test measure?
Prostate-specific antigen is a kallikrein serine protease produced by prostatic epithelium that liquefies seminal fluid. It circulates in free and protein-complexed forms, the sum of which is total PSA. Although prostate-specific, it is not cancer-specific, rising with benign prostatic hyperplasia, prostatitis, prostatic manipulation, and age as well as malignancy.
Total PSA is the primary marker for prostate cancer detection and monitoring, but its specificity is limited in the intermediate range. Pairing it with free PSA to derive the percent free PSA improves discrimination between benign and malignant causes, particularly when total PSA is between roughly 4 and 10 ng/mL, helping refine the decision to proceed to biopsy.
Free PSA is the fraction of PSA circulating unbound to protease inhibitors such as alpha-1-antichymotrypsin. The proportion of PSA that is free tends to be lower in prostate cancer, where more PSA circulates in complexed form, than in benign prostatic conditions. Free PSA is labile and requires appropriate specimen handling, as the free fraction degrades if processing is delayed.
Free PSA is measured chiefly to calculate the percent free PSA (free divided by total). It is not interpreted as a standalone value; its purpose is to refine the meaning of an elevated total PSA by indicating the likelihood that the elevation is benign or malignant.
Percent free PSA is calculated as free PSA divided by total PSA, expressed as a percentage. It integrates the two measurements into a single index that better discriminates benign from malignant causes of an elevated total PSA than total PSA alone. It is most informative when total PSA is in the intermediate range and the digital rectal examination is unremarkable.
Percent free PSA is the key derived value of the panel. A lower percentage is associated with a higher probability of prostate cancer, while a higher percentage favours benign prostatic hyperplasia, helping to inform whether a man with an intermediate total PSA should proceed to biopsy.
Why is the PSA Free + Total test ordered?
- Refinement of an intermediate total PSA (roughly 4–10 ng/mL) to inform the decision about prostate biopsy
- Evaluation of men with a raised total PSA but an unremarkable digital rectal examination, where percent free PSA aids discrimination
- Assessment of men in whom avoiding an unnecessary biopsy is a priority and additional risk discrimination is wanted
- Risk stratification alongside age-specific PSA thresholds, PSA density, and velocity in the prostate cancer pathway
- Shared-decision prostate cancer assessment where the percent free PSA contributes to weighing benefits and harms
- Follow-up of a previously borderline total PSA where added specificity from the free fraction is helpful
- Evaluation of men with a family history of prostate cancer and an intermediate total PSA
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No — however, the sample should be taken before, or appropriately after, ejaculation, digital rectal examination, or prostatic instrumentation, which transiently raise PSA
Collection method
Venipuncture at patient service centre
Turnaround
1–3 business days
Collection notes
Process promptly and store appropriately, as free PSA is labile and degradation distorts the percent free PSA. Avoid sampling soon after ejaculation, digital rectal examination, catheterisation, or biopsy, and defer during prostatic or urinary infection. Document 5-alpha reductase inhibitor use, use the same assay for monitoring, and withhold high-dose biotin for 48–72 hours beforehand.
Specimen requirements
Minimum 0.5 mL serum, processed promptly to preserve free PSA. Separate serum from cells and store per LabCorp protocol; follow LabCorp stability and transport guidelines.
What can affect PSA Free + Total results?
Free PSA degrades if the specimen is not processed and stored appropriately, distorting the percent free PSA. Prompt separation and correct storage per protocol are essential for a reliable ratio.
Benign enlargement and inflammation raise total PSA and tend to raise the percent free PSA; prostatitis in particular should be allowed to resolve before testing to avoid a misleading result.
Ejaculation, digital rectal examination, catheterisation, and biopsy transiently raise PSA and can alter the free-to-total relationship, so timing of the sample matters.
These drugs lower total PSA by roughly half over months; the total must be interpreted against a treatment-adjusted baseline, and the effect on the percent free PSA should be considered.
Total and free PSA assays differ in calibration, and the percent free PSA cut-off depends on the assay, so serial monitoring should use the same method and results interpreted against the performing laboratory's reference.
Biotin can interfere with streptavidin-biotin immunoassay platforms, altering PSA measurements. Patients should withhold high-dose biotin for 48–72 hours before collection.
What do PSA Free + Total results mean?
Elevated
An elevated total PSA with a low percent free PSA raises the probability of prostate cancer and supports proceeding to further evaluation such as MRI and biopsy. Benign causes — benign prostatic hyperplasia, prostatitis, recent prostatic activity — should still be excluded, and the result interpreted with age-specific thresholds and the clinical picture.
Normal
A total PSA within the age-appropriate range with a reassuring percent free PSA suggests a lower likelihood of clinically significant prostate cancer, though no result excludes it entirely. Serial trends and the overall clinical assessment remain important.
Reduced
A higher percent free PSA in a man with an intermediate total PSA favours benign disease and lowers the estimated cancer probability, which may support surveillance rather than immediate biopsy. A low total PSA is generally reassuring but does not entirely exclude cancer.
Note: Percent free PSA is most useful when total PSA is intermediate and the examination is unremarkable; it refines risk but does not diagnose or exclude cancer. Free PSA is labile, so specimen handling strongly affects the ratio, and assays and cut-offs differ, so the same method should be used for monitoring. The panel is interpreted within a structured pathway alongside age-specific thresholds, imaging, and clinical findings, and 5-alpha reductase inhibitors and recent prostatic activity must be accounted for.
Frequently asked questions
It measures free PSA in addition to total PSA and derives the percent free PSA, which improves specificity in the intermediate range. A lower percentage favours cancer and a higher percentage favours benign disease.
How to access the PSA Free + Total test
The PSA Free + Total reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: June 2, 2026
Last reviewed: June 2, 2026
- Catalona WJ, et al. Use of the percentage of free PSA to enhance differentiation of prostate cancer from benign prostatic disease. JAMA. (1998)
- Mottet N, et al. EAU-EANM-ESTRO-ESUR-SIOG Guidelines on Prostate Cancer. Eur Urol. (2021)
- Lee R, et al. A meta-analysis of the performance characteristics of the free prostate-specific antigen test. Urology. (2006)
- US Preventive Services Task Force. Screening for Prostate Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. (2018)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.
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