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In this Article

• What is the Prostate Specific Antigen?
• How is PSA measured?
• What are normal results for the PSA test?
• How is PSA used to detect prostate cancer?
• What other conditions can cause an abnormal PSA level?
• What is the free PSA test?
• What are the limitations of the PSA test?
• PSA Test At A Glance
• Prostate Specific Antigen Index

What other conditions can cause an abnormal PSA level?

Other diseases that affect the prostate gland can cause an elevated PSA. The most frequent problem is known as benign prostatic hypertrophy (enlargement) or hyperplasia (BPH). This condition is due to an increase in the size of the prostate gland that typically occurs with aging. Infection of the prostate gland (prostatitis) is another relatively common affliction that can also cause an abnormal elevation of PSA. Other conditions include poor blood supply to the prostate gland, instrumentation of the urethra (drainage tube from the bladder), urinary retention, and prostate biopsy.

What is the free PSA test?

Most of the PSA protein released into the blood becomes attached to other blood proteins. The PSA that does not become attached is known as free PSA and can be measured. It has been found that the level of free PSA is decreased in men who have prostate cancer compared to those with benign conditions. The exact level depends upon which test the laboratory uses, but generally less than 10% free PSA is suggestive of cancer. This test is most helpful when the usual PSA test is between 4 and 10 ng/mL.

What are the limitations of the PSA test?

A few percent of prostate cancers do not produce detectable increases in the blood PSA, even with advanced disease. Many early cancers will also not produce enough PSA to cause a significantly abnormal blood level. It is therefore important not to rely only on blood PSA testing.

The most useful additional test is a physical prostate examination by a doctor known as the digital rectal exam (DRE). During this examination a doctor inserts a finger into the rectum to feel the prostate for lumps, size, shape, tenderness, and hardness.

PSA Test At A Glance

• The PSA test is a blood test.
• The PSA test can be used to suggest the presence of or monitor prostate cancer.
• The PSA test can be abnormal with benign enlargement and infection of the prostate gland.
• The PSA test can be elevated with other conditions that irritate the prostate gland.