PSA testing is used to screen for prostate cancer. PSA testing may also be used to make treatment decisions.

By Mayo Clinic Staff

A PSA test measures the amount of prostate-specific antigen (PSA) in your blood. PSA testing is used primarily to screen for prostate cancer.

PSA is a protein produced in the prostate, a small gland that sits below a man's bladder. PSA is mostly found in semen, which also is produced in the prostate. Small amounts of PSA ordinarily circulate in the blood.

Men with prostate cancer may have elevated levels of PSA. Many noncancerous conditions also can increase a man's PSA level. Although the PSA test can detect high levels of PSA in the blood, the test doesn't provide precise diagnostic information about the condition of the prostate.

The PSA test is only one tool used to screen for early signs of prostate cancer. Another common screening test, usually done in addition to a PSA test, is a digital rectal exam. In this test, your doctor inserts a lubricated, gloved finger into your rectum to reach the prostate. By feeling or pressing on the prostate, the doctor may be able to judge whether it has abnormal lumps or hard areas.

Neither the PSA test nor the digital rectal exam provides enough information for your doctor to diagnose prostate cancer. Abnormal results in these tests may lead your doctor to recommend a prostate biopsy. During this procedure, samples of tissue are removed for laboratory examination. A diagnosis of cancer is based on the biopsy results.

For men who have already been diagnosed with prostate cancer, the PSA test may be used to:

  • Help decide if and when to begin treatment
  • Judge the effectiveness of a treatment
  • Check for recurring cancer
May 29, 2014