What is the PSA test?

The PSA test measures the amount of prostate specific antigen (PSA) in the blood. PSA is a protein produced by normal and cancerous cells in the prostate.

It is normal to have a small amount of PSA in the blood, and the amount rises as men age and the prostate gets bigger. A raised PSA level may suggest there is a problem with the prostate, but not necessarily cancer. The PSA test can find aggressive prostate cancer that needs treatment, but it can also find slow-growing cancer that may never cause symptoms or shorten life.

There is no official screening programme in the UK to look for prostate cancer. The PSA test is currently offered to patients who present with symptoms which could be due to prostate cancer but also to men who request it after they have been appropriately counselled. If men choose to have their PSA levels tested, they should be fully informed of the advantages and disadvantages of this test.

What can affect a PSA test result?

Things to consider when discussing a PSA test

Patient profile

George is a 65 year-old, well-educated, retired manager of an NHS department. George and his wife are financially secure and enjoying their retirement. They frequently go on cruises and other holidays abroad. In his spare time George plays golf with other managers from his former place of work. George is visiting his GP to ask for a PSA test following the death of a friend’s brother from prostate cancer. He has heard from friends that at his age he should have his PSA checked. He is asymptomatic, yet requests a PSA test from his GP as a screening process for prostate cancer.

Key points:

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Advantages

• Earlier diagnosis – PSA testing can help diagnose prostate cancer before symptoms present
• Early staging – PSA testing may help to identify a fast-growing cancer at an early stage when treatment may stop the cancer spreading
• High-risk monitoring – Having regular PSA tests may be helpful for men who are more at risk of prostate cancer. This can help spot any changes in the PSA level, which might be a sign of prostate cancer

Disadvantages

• False-positive results – A PSA test can return a raised PSA level, even if the patient does not have prostate cancer (a false-positive result). 75% of men with a raised PSA level will turn out not to have any kind of prostate cancer
• False-negative results – The PSA test can miss prostate cancer. 1 in 7 men (15%) with a normal PSA level will have prostate cancer, some with clinically relevant false negative i.e. Gleason score>7. 1 in 50 men (2%) with a normal PSA may have a fast-growing prostate cancer (Prostate Cancer UK, 2018)
• Unnecessary procedures – If the PSA level is raised this might necessitate more tests. Although most men are now offered an MRI scan before a biopsy, some men may have invasive, and sometimes painful, biopsies for no reason. The biopsy can cause side effects, such as infection and blood in the urine and semen
• Clinically insignificant cancer detection – A raised PSA level might result in a diagnosis of a slow-growing prostate cancer which would never have caused the man any problems or shortened his life. However, being diagnosed with cancer could lead to unnecessary worry, and lead to avoidable treatment
• Unnecessary treatment – Unnecessary treatments for prostate cancer have side effects that can affect daily life, including urinary, bowel, and erection problems

Recognising and referring suspected prostate cancer is tricky for primary care professionals. If you consider a PSA test to be indicated for a patient presenting with urological symptoms, or if an asymptomatic patient requests a PSA you should have a discussion with your patient about the potential harms and benefits.

See the table below for NICE NG12 Guidance. It is important that PSA testing and the following guidance is used alongside clinical judgement and informed conversations with patients.

Age-specific PSA thresholds for people with possible symptoms of prostate cancer: 

NB: Following guidance from the NHS Prostate Cancer Risk Management Programme (PCRMP) – in asymptomatic men, if the PSA is over 3µg/L the GP is advised to use their clinical judgement to decide whether a referral is appropriate.

Additional resources

Link: What is a PSA test, Cancer Research UK
Link: 10 Top Tips – PSA Testing, Macmillan Cancer Support
Link: Prostate cancer screening, Cancer Research UK (2019)
Link: The PSA Test, Prostate Cancer UK
Link: Prostate cancer – PSA Testing, NHS (2021)
Link: Prostate cancer screening with prostate-specific antigen (PSA) test: a clinical practice guideline, The British Medical Journal (2018)
Link: NHS Prostate Cancer Risk Management Programme overview (PCRMP)