PSA test for prostate cancer

What is the PSA test?

PSA (Prostate Specific Antigen) is an enzyme (a protein) substance made by the prostate gland. It is made by both normal cells and cancer cells (if present), and is secreted into the seminal fluid to keep it liquid. A small amount of PSA continually leaks from the prostate gland into the blood stream. Cancer cells produce more PSA than normal cells, and when prostate cancer cells multiply, more PSA spills into the blood. The PSA test measures the level of PSA in the blood.

So a raised PSA can be an early indication of prostate cancer. But other conditions, such as benign (non-cancerous) enlargement of the prostate, inflammation or infection, can also cause a rise in PSA, a 'false positive'. And it is also possible to have cancer but have a 'normal' PSA result; this is called a 'false negative'. 

Although men did not know much about the PSA test, some of those we talked to knew what PSA stood for and could explain why the test is done. 

But many other men we talked to seemed confused and expressed misunderstanding. One man, for example, suggested that too much PSA allowed the cancer to grow, and he said it was important to 'kill the amount of PSA manufactured by the prostate gland'. Some men found it hard to explain what a rise in PSA level in the blood might indicate, and others didn't know what the letters PSA meant. 

The PSA test is available in the National Health Service. A small sample of blood is taken from the arm. This is usually done in a GP's surgery or in a hospital clinic. The men we interviewed stressed that it was just like any other 'normal' blood test, but there are advantages and disadvantages of having the test and GPs have been told to inform men about the possible benefits and drawbacks of having a test before proceeding.

Public Health England has developed the Prostate Cancer Risk Management Programme (PCRMP):

The aim of the Prostate Cancer Risk Management Programme (see resources) is to ensure that men who are concerned about the risk of prostate cancer receive clear and balanced information about the advantages and disadvantages of the PSA test and treatment for prostate cancer. This will help men decide whether they want to have the test.

The information is available to assist GP's in the counselling of otherwise well men who enquire about testing. It helps the primary care team to provide men with information on the benefits and limitations of the PSA test. It comprises a full evidence document, a summary sheet for primary care teams and a patient information sheet that GPs can print off for men.

A digital rectal examination is often seen as an important part of the prostate examination. Some other factors, such as ejaculation, urinary infection or a prostate biopsy in the last 6 weeks can also affect the PSA level in the blood, making it appear abnormally raised. It is not clear whether or not vigorous exercise, such as cycling, affects the PSA level, but doctors had told some men to avoid such activity just before their PSA test and the PCRMP information also recommends not having a PSA test for 48 hours after heavy exercise

Some medicines may also affect the PSA result. One man had heard that herbal remedies such as saw palmetto, which is sometimes used for benign prostate enlargement, could artificially 'dampen' the PSA level although there is currently no evidence of this.

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In future other more accurate ways to diagnose prostate cancer may be developed. Scientists are continuing to look for new ways to diagnose prostate cancer.

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Some men gave reasons for having the test while others explained why they had decided not to have one. The men we talked to also explained how they decided whether or not to have the test (see 'Deciding whether or not to have the PSA test').

Last reviewed May 2016.

Last updated May 2016.



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