Prostate-specific antigen (PSA) is a protein produced exclusively by prostate cells. There is a simple blood test to measure your PSA level and this may help to detect early prostate cancer.

The chance of having prostate cancer goes up as your PSA level increases (see table below). Small amounts can also be found in the blood of healthy men as doctors have not yet determined what is a ‘normal’ level.

If you do not know your PSA level or prefer not to have a test at this time you can assess your risk by using Risk Calculator 1 which takes into account your age, family history and any urinary symptoms (more). You can use Risk Calculator 2 to assess your risk if you know your PSA level.

However, if your PSA is above 3 or 4 ng/ml your doctor may want to do a biopsy. This would involve taking one or more samples from your prostate gland to give them a clearer picture.

PSA value in blood	Risk of finding prostate cancer at biopsy
Less than 2.0 ng/ml	7.1%
Between 2.0 and 3.9 ng/ml	18.7%
Between 4.0 and 5.9 ng/ml	21.3%
Between 6.0 and 7.9 ng/ml	28.6%
Between 8.0 and 9.9 ng/ml	31.7%
10.0 ng/ml or more	56.5%
Based on biopsies from 2267 men who were Rotterdam participants in the European Randomized Study of Screening for Prostate Cancer (ERSPC).

Thirteen per cent of men over 55 have  a PSA level  of ≥ 4 ng/ml but this does not automatically mean you have cancer. An elevated level can also be due to other conditions, such as benign enlargement of the prostate (BPH), a urinary tract infection or a prostate infection.

Neither the PSA test nor the rectal examination (DRE) is 100% accurate and can give an abnormal result even when cancer is not present (known as a false positive result). In addition, normal results can occur even when cancer is present (false negative).

As seen in the table a small number of men with a low PSA level may still have prostate cancer although this is usually likely to be at a very early stage. A normal result for a man over 55 can be reassuring as it indicates you are unlikely to have an aggressive cancer at the time of being tested.

Before deciding to refer you to a urologist, your doctor will consider a range of factors including your age and family history. Once you are referred to a specialist, it could mean you will have to undergo further medical tests that might possibly affect the quality of your life.

What to consider before having a PSA test

• The test may help to find prostate cancer at an early stage even before there are symptoms. (more)
• However, many small prostate cancers detected by PSA would never develop enough to cause any symptoms.
• A low test result can be very reassuring.
• Even if your level is raised, this could be for reasons other than prostate cancer and you may have unnecessary stress while this is checked out.
• With a high PSA level you may need further tests such as a biopsy, which can be painful and lead to blood in urine, semen or stools. Occasionally having a biopsy can lead to infection of the prostate gland, which can be difficult to treat.
• In a small number of men, a biopsy may not always detect a significant cancer even when it is present.