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Prostate-specific antigen (PSA), total and free

Tumor Markers · also called tPSA, fPSA, Free PSA ratio

What it measures

PSA is a protein produced by prostate cells. Total PSA is used in prostate cancer screening after informed discussion and in monitoring treated cancer; the free PSA percentage helps decide on biopsy when total PSA is 4–10 ng/mL.

Specimen and preparation

Specimen: Serum or lithium-heparin plasma
Tube: Gold top
Preparation: Avoid ejaculation for 48 hours, vigorous cycling, and sampling soon after digital rectal exam, catheterisation or biopsy.

Reference range

Group	Range
Male 40–49 years (total)	<2.5 ng/mL
Male 50–59 years (total)	<3.5 ng/mL
Male 60–69 years (total)	<4.5 ng/mL
Male 70–79 years (total)	<6.5 ng/mL
Free/total ratio (total 4–10)	>25% favours benign

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Prostate cancer
Benign prostatic hyperplasia
Prostatitis and urinary infection
Urinary retention or instrumentation

Causes of low values

5-alpha-reductase inhibitors (finasteride, halves PSA)
After prostatectomy (should be undetectable)
Obesity (dilution)

Method

Chemiluminescent immunoassay

Good to know

Free PSA below 10% raises the probability of cancer. A rising PSA after radical treatment indicates biochemical recurrence.

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