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The Prostate Specific Antigen (PSA) test - what is it?

Prostate Specific Antigen (PSA) is a chemical produced normally by prostate cells. It is a type of chemical known as an enzyme, and it is believed to have a role in liquefying semen after ejaculation (which may help in sperm motility).

PSA testing can help diagnose prostate cancer in early stages when it may be localised to the prostate gland and can be treated.

PSA is only produced by prostate cells (it is prostate specific), but is produced by both cancerous and non-cancerous prostate cells (it is not cancer specific). Although PSA is the best example we have of a marker for prostate cancer this non-specificity for cancer means that there are reservations about the interpretation of raised values.

Essentially, one of the following scenarios may commonly occur

  • A man with prostate cancer may not have a raised PSA test (this is known as a false-negative result)
  • A man with a raised PSA may not have prostate cancer (this is known as false-positive result)


Current recommendations for Further Investigations

The current recommendations for further investigations are that if either the DRE is abnormal, or the PSA test is raised above the age adjusted limit then further investigations should be performed.

Should I have a PSA test, and what will it mean?

If a PSA test is performed and is normal this is not cast-iron proof that you do not have prostate cancer, and your doctor may still wish to perform further tests if your prostate feels abnormal. Equally if your PSA is raised this does not necessarily mean that you do have prostate cancer.

If you choose to have a PSA test done you should be prepared to undergo a prostate biopsy if the PSA value is sufficiently raised to justify this course of action.

Further information is available from the following web site:


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