Lab test

Prostate-Specific Antigen (PSA), Free-to-Total Ratio

This blood test measures both free PSA and total PSA and calculates their ratio, the free-to-total PSA ratio.

Typical price

From $178

Results

1-3 business days

Preparation

See preparation notes below

Sample

Blood draw or sample collection at a local center

This blood test measures both free PSA and total PSA and calculates their ratio, the free-to-total PSA ratio. PSA circulates in the blood partly bound to proteins and partly unbound, and the proportion that is free can add information when a total PSA result is borderline. A lower free-to-total ratio is more often associated with prostate cancer, while a higher ratio is more common in benign prostate enlargement. The test is ordered to help clarify an elevated or ambiguous total PSA result and to support decisions about whether further prostate evaluation is appropriate. Results are interpreted by a healthcare provider with age and other findings.

• Free PSA The unbound portion of prostate-specific antigen circulating in the blood.
• Total PSA All prostate-specific antigen, both bound and unbound.
• Free-to-Total PSA Ratio The proportion of PSA that is free, calculated from the two measurements.

• Men with a borderline or elevated total PSA result
• Individuals being evaluated for possible prostate disease
• Men whose healthcare provider wants additional PSA detail
• Those with an abnormal prostate examination

• Inform the laboratory of recent prostate procedures, since these can affect PSA
• Avoid strenuous cycling or ejaculation shortly before the draw unless told otherwise
• Report medications for prostate conditions to your provider

The free-to-total ratio is interpreted together with the absolute total PSA value. A lower ratio can raise concern for prostate cancer, while a higher ratio is more often seen with benign prostate enlargement, but neither is conclusive. The ratio is most useful when total PSA is in a borderline range. A healthcare provider should interpret the result with your age, examination findings, and whether additional evaluation is recommended.

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