Understanding the PSA Test

The PSA test is a blood test that measures the amount of prostate specific antigen (PSA). PSA is a protein produced by normal cells in the prostate and by prostate cancer cells. It is normal for men to have a small amount of PSA in their blood, and the amount rises slightly as they get older and the prostate gets bigger. A raised PSA level may suggest a problem with the prostate, but not necessarily cancer.

Advantages of a PSA test

• It can help pick up prostate cancer before you have any symptoms.
• It can help pick up a fast-growing cancer at an early stage, when treatment could stop it spreading and causing problems.
• A regular PSA test could be helpful, particularly if you have an increased risk of prostate cancer, for example with family history. This could detect any unusual increase in your PSA level that might be a sign of prostate cancer.

Disadvantages of a PSA test

• Your PSA level might be raised, even if you do not have prostate cancer. Many men with a raised PSA level do not have prostate cancer.
• The PSA test can miss prostate cancer. For example, one major study showed that 1 in 7 men (15 per cent) with a normal PSA level may have prostate cancer, and 1 in 50 men (two per cent) with a normal PSA level may have a fast-growing cancer.
• If your PSA level is raised you may need an MRI scan and if that is abnormal, you may need a biopsy, which is usually performed under local anaesthetic. This can cause side effects, such as pain, infection (1 in 300 people) and mild bleeding in urine and semen.

Being diagnosed with a slow-growing prostate cancer that is unlikely to cause any problems or shorten your life may still make you worry, and may lead you to have treatment that you do not need. However, most men with low-risk, localised prostate cancer now have their cancer carefully monitored instead, and only have treatment if the cancer starts to grow. 

For more information about the PSA test, click here.