The PSA test is a blood test. PSA (Prostate Specific Antigen) is a protein made by the prostate gland, which naturally leaks out into the bloodstream. The PSA test measures the level of PSA in your blood. It can take up to two weeks to get the result of a PSA blood test.
Sometimes a raised PSA level can be a sign of prostate cancer. More often though, it is caused by something less serious like an inflamed prostate (prostatitis); or an enlargement of the prostate that often comes with ageing (benign prostatic hypertrophy, or BPH). A single PSA test can’t show you whether a prostate cancer is present, or whether it is slow- or fast-growing.
The level of PSA can also be raised by:
- infections
- prostate biopsies – PSA should not be tested until six weeks after a biopsy
- having a urinary catheter (a tube to drain urine)
- prostate or bladder surgery – PSA should not be tested until six weeks after surgery
- prolonged exercise – such as long-distance running or cycling – may raise PSA for up to 48 hours
- ejaculation – may raise PSA for up to 48–72 hours
Some drugs such as finasteride (Proscar®), which is given to help with urinary symptoms caused by an enlarged prostate gland, can lower the level of PSA in the blood, so this needs to be taken into account. It is important to tell your GP about any medicines you are taking.
How reliable is it?
- The PSA test is not a test for prostate cancer. It is a test for abnormalities of the prostate, one of which may be cancer.
- Two out of three men with a raised PSA will not have any cancer cells in their prostate biopsy.
- Up to one in five men with prostate cancer will have a normal PSA result.
Screening for prostate cancer
In the UK, there is currently no screening programme for prostate cancer using the PSA test. This is because there isn’t a reliable test or enough evidence to prove that a screening programme would be worthwhile. However, the Department of Health has said that any man over 50 who would like the PSA test can contact their GP who will then discuss the pros and cons of the test with them. If the man then decides he would like to go ahead with the test then his GP will arrange it for him. Alternatively the PSA test is widely available, for a small charge, at many pharmacies and private clinics.