Prostate-Specific Antigen (PSA) Test

Why this test may be ordered

• To screen for prostate cancer before symptoms appear
• To help diagnose the cause of prostate conditions that are not cancer
• To monitor treatment for a prostate condition, including cancer

Preparation and collection

Avoid having sex or masturbating for 24 hours before the test, as releasing semen can increase PSA levels and affect accuracy. Tell your provider about any medicines you take, but do not stop taking any unless instructed.

A health care professional will take a blood sample from a vein in your arm, using a small needle. The procedure usually takes less than five minutes.

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

There is no specific normal or abnormal level for PSA in blood. In general, the higher your PSA level, the more likely it is that you have cancer, but it is possible to have a high PSA without prostate cancer or a low PSA with prostate cancer. Interpretation should be discussed with your healthcare provider.

• Low PSA level: It is normal to have a low level of PSA in your blood. A low PSA level is generally reassuring, but it is possible to have prostate cancer with a low PSA. Limitation: A low PSA does not completely rule out prostate cancer. Next step: Routine
• High PSA level: May be caused by prostate cancer, an enlarged prostate (benign prostatic hyperplasia), prostatitis (inflammation of the prostate), other common prostate problems, urinary tract infections, or certain medicines. The test cannot tell which condition is causing the high level. Limitation: A high PSA level does not confirm cancer. Only a prostate biopsy can diagnose cancer. Biopsy carries risks such as bleeding, blood in semen or urine, infection, or difficulty urinating. Next step: Your provider may recommend additional tests such as another PSA test, a digital rectal exam (DRE), a urine test, or a prostate biopsy. Discuss the need for follow-up with your provider.

• A PSA test cannot distinguish between abnormal PSA levels from prostate cancer and noncancerous conditions.
• If PSA is high, a prostate biopsy is the only way to find out if the cause is cancer; biopsies have possible harms (bleeding, infection, difficulty urinating).
• PSA screening may lead to finding and treating prostate cancer that would never have affected your health, and treatment may cause serious harms such as erectile dysfunction, urinary incontinence, or bowel incontinence.
• It can be difficult to tell the difference between slow-growing cancers and those likely to spread.

What to do next

If you have questions about your results, talk with your provider. For screening, discuss your risk, general health, and preferences to decide if PSA testing is right for you.

• What is my risk for developing a serious type of prostate cancer?
• Is my general health good enough to have treatment for prostate cancer if it is found?
• What are the possible benefits and harms of screening, diagnosis, and treatment for me?

Evidence source

U.S. National Library of Medicine: Prostate-Specific Antigen (PSA) Test