Prostate specific antigen (PSA) tests
What is a prostate specific antigen (PSA) test?
A PSA test measures the amount of prostate specific antigen in the blood. PSA is a protein produced by the prostate, a golf ball sized gland that sits just below a man’s bladder. It helps to liquefy the semen (the fluid produced when you ejaculate). A small amount of PSA also enters the bloodstream, and this can be detected by a PSA test. PSA levels in the blood may be higher than normal if you have certain conditions, such as prostate infection, inflammation, enlargement or cancer.
Who should have a PSA test?
The PSA test has been recommended by some experts as a method of screening for prostate cancer in healthy men. However, medical organisations differ in their recommendations about the benefits of PSA screening, and about which men should have it and at what ages.
In Australia, the Royal College of Pathologists of Australasia and the Urological Society of Australia and New Zealand believe men who wish to assess their risk of prostate cancer should have a baseline PSA test, along with a digital rectal examination (DRE — an examination in which the doctor inserts a gloved finger into the rectum to feel for abnormalities in the prostate), from around the age of 40. They would then have follow-up tests each year or less often — depending on their test results — to monitor any changes. The Urological Society also recommends screening for healthy men aged 55-69 years.
Currently, however, Cancer Council Australia and the Royal Australian College of General Practitioners (RACGP) believe there is not enough evidence to recommend the PSA test as a routine screening test for prostate cancer in healthy men. Available evidence suggests that it does not reduce deaths from prostate cancer and that the harms of investigations and treatment may outweigh the risk of having an undiagnosed or untreated cancer. The Cancer Council and RACGP recommend that men talk over the risks and benefits of the PSA test with their doctor before deciding whether they should have this test.
However, if you have already been diagnosed with prostate cancer, regular PSA testing may be done to monitor the cancer. This may be as part of a ‘watchful waiting’ approach — if the cancer is thought unlikely to spread or cause problems, doctors may monitor it using PSA tests and other investigations rather than treating it straight away. Alternatively, if you have had treatment for prostate cancer, PSA tests may be done to assess the effects of that treatment.
How should I decide whether to have a PSA test?
If you are thinking of having a PSA test for screening purposes, you should see your GP to talk over the risks and benefits of the test — and those of further investigations or treatment if the PSA test is abnormal.
One concern is that the PSA test is not that good at detecting prostate cancer — only one in 3 men with an abnormal PSA test is found to have prostate cancer. The 2 in 3 men who don’t have prostate cancer will have ‘false positive’ PSA results, which can cause anxiety and lead to further procedures that could have side effects. In addition, the PSA test is sometimes negative in men who do have prostate cancer (a ‘false negative’ result).
The other issue is that a PSA test alone cannot tell slow-growing cancers (which may not cause problems) from more aggressive cancers that could endanger life. PSA testing has so far not been proven to reduce the risk of dying from prostate cancer.
To check whether a raised PSA level is caused by cancer, and how aggressive the cancer is, requires a prostate biopsy (where small pieces of tissue are taken for examination under the microscope).
When advising you, your doctor will take into account your age and any symptoms you have. He or she will also consider factors that increase your risk of prostate cancer, such as a family history of prostate cancer and having had a previous abnormal PSA test or prostate biopsy.
Having the PSA test may be more worthwhile if you have risk factors for prostate cancer than if you don’t — but whether to have the test is still an individual decision. To some extent, it depends on how you feel about cancer, investigations, treatment and your overall health. Your doctor can help you clarify what’s important to you.
How is the PSA test done?
The PSA test is done by taking blood from a vein — usually in your arm — and sending it to the lab for analysis.
How should I prepare for a PSA test?
Before you have a PSA test, tell your doctor about any medicines, supplements or herbal products you are taking, as they may affect the results. One medicine in particular, finasteride (e.g. Propecia, Proscar), which is used for treating baldness and benign prostatic hypertrophy (non-cancerous enlargement of the prostate), can affect PSA results.
You should also tell your doctor if you have had any urinary problems or investigations of the urinary tract such as a prostate biopsy or cystoscopy in the few weeks before a PSA test is scheduled, as these can also affect the results.
As ejaculation can make PSA levels rise briefly, some doctors recommend avoiding sexual activity for 48 hours before a PSA test.
Are there any risks or side effects of a PSA test?
The PSA test, like other blood tests, is not likely to cause any problems other than momentary discomfort.
What if my PSA result is abnormal?
Your doctor will interpret the results of the PSA test on the basis of your age — PSA levels tend to increase naturally as men get older. He or she may also consider other findings, such as whether your prostate feels abnormal on digital rectal examination.
After taking these factors into account, if your doctor considers your PSA result is abnormal, he or she may suggest repeating it or referring you to a specialist for a further opinion or investigations. There are many potential reasons for a raised PSA level, including infection, inflammation and non-cancerous enlargement of the prostate.
Last Reviewed: 19 August 2011
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