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.
Thus 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 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.
“The aim of Prostate Cancer Risk Management 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 to decide whether they want to have the test.
Information packs have been sent to General Practitioners to assist them in the counselling of men who enquire about testing. The pack will help the primary care team to provide men with information on the benefits and limitations of the PSA test. It comprises a reference booklet and summary sheet for the primary care team and a book of tear off patient information sheets."
A digital rectal examination is often seen as an important part of the prostate examination. But because a rectal examination may raise the PSA level and lead to a false reading a PSA test should not be done immediately after it. Some other factors, such as ejaculation, 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.
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.
In future other more accurate ways to diagnose prostate cancer may be developed, perhaps by measuring levels of 'free PSA', not attached to other proteins, and levels of 'bound PSA' (complexed PSA or cPSA) which is attached to another protein. Men who do not have cancer are thought to have higher levels of free PSA than men with cancer. Several clinical trials have now been done to see whether cPSA measurements are more reliable in diagnosing prostate cancer than the usual PSA test, but so far the results of these studies are conflicting (see Cancer Help UK for more information).
The methods of testing free and bound PSA vary and doctors do not agreed on the ratios of free to bound PSA that indicate cancer. So it is not used routinely in diagnosing prostate cancer. You are more likely to have it done if your standard PSA test result was borderline.
The PCA3 test is new urine test. PCA3 stands for Prostate CAncer gene 3. Prostate cells have PCA3 genes. These genes make the prostate cells produce a small amount of a particular protein. Prostate cancer cells make much more of this protein than normal cells. When the level of PCA3 protein is high, it leaks into the urine which can be measured by a urine test. The test is not yet available on the NHS. But so far, trial results have been promising, and it may be used more often in the future.
Researchers in the USA have recently identified another protein, which they have called EPCA [early prostate cancer antigen]. They suggest that testing for this protein may be a better way of diagnosing prostate cancer, but this is new research which needs confirmation. One man spoke enthusiastically about this new research.
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 October 2010.
Last updated October 2010.
