What you should know about the PSA

The PSA test measures levels of a substance in the blood (Prostate Specific Antigen) that can signal a problem in the prostate. The test has been, and continues to be, one of the more controversial areas of medicine.

This is because some experts (including ourselves) believe it to be a useful tool – the best we currently have – in indicating your risk of having prostate cancer.

Others, including many GPs and some specialists, believe it does more harm than good because it is unreliable: it can give false positive or false negative results. They say false positive readings can lead to many men having unnecessary, sometimes painful prostate biopsies which carry a risk of infection and create considerable anxiety. They say there’s no clear proof that treating prostate cancer, once diagnosed, has any significant impact on a man’s life expectancy. They say, in effect, “Don’t bother with PSA; don’t bother if you have prostate cancer – just forget about it”.

This attitude troubles us deeply. For what are we to say to the families of the 10,000 men in the UK who die each year of prostate cancer? Each one would have had a chance of cure if the disease had been caught at an early enough stage.

PSA in diagnosis

While it’s true that mass screening for prostate cancer is not economically viable for the NHS, and while the PSA may involve an element of misdiagnosis, its detractors are missing the point. PSA does not “diagnose” cancer as high readings can often be caused by other, non-cancerous prostate conditions. The PSA test should be regarded only as an indication that something might be wrong. Only biopsies can confirm the presence of prostate cancer.

A one-off high PSA reading (usually above 4ng/ml, but this depends on age), considered with the doctor’s findings on digital rectal examination of the prostate (DRE), can either ring alarm bells indicating the need for biopsy, or suggest that it’s wise to keep a watchful eye and see if the PSA levels rise over time (“active surveillance”).

Our view is that knowledge is power, and that a man is wise to know his PSA value. We also think it’s wise to make sure that you have expert guidance in the interpretation of your results.

PSA in monitoring

PSA measurements over time can provide valuable information. Watching the rate of increase helps us fine-tune diagnosis. But in addition, after treatment for prostate cancer, by surgery or radiotherapy, ongoing PSA testing can provide all-important information about the response to therapy and the risk of relapse.