Prostate-specific antigen (PSA) blood test
Prostate-specific antigen, or PSA, blood test is used to help diagnose prostate cancer.
However, an increased PSA level can also indicate an enlarged prostate, prostatitis or a urinary infection.
If PSA levels are raised, a biopsy tissue sample may be taken from the prostate for laboratory testing to check for cancer.
There is no routine NHS screening programme for prostate cancer because misleading test results could result in unnecessary distress and treatment.
PSA levels are measured in nanograms per millilitre of blood (ng/ml). Whether a PSA level is “normal” depends on the individual and their age. Cancer Research UK uses the following rough guide:
- 3 ng/ml or lower is considered in the normal range for a man under 60 years old
- 4 ng/ml or lower is normal for a man between 60 to 69 years old
- 5 ng/ml or lower is normal for a man 70 years old and over
A reading higher than 5ng/ml but lower than 10 ng/ml is usually due to a benign enlarged prostate, Cancer Research UK says. A reading above 10 ng/ml may also indicate benign prostate disease. However the higher the PSA level, the more likely it is to be prostate cancer.
Most men have PSA levels under 4 ng/ml, and traditionally this has been used as the cut-off point for concern about the risk of prostate cancer. Men with prostate cancer often have PSA levels higher than four, although cancer is a possibility at any PSA level. According to published reports, men who have a ‘normal’ PSA level below 4 ng/ml have a 15% chance of having prostate cancer. Those with a PSA level between four and 10 have a 25% chance of having prostate cancer and if the PSA is higher than 10, the risk increases to 67%.
Just as significant as the PSA level is the trend in that number (whether it is going up, how quickly and over what period of time). It is also important to understand that the PSA test is not infallible. Most men with elevated PSA levels have non-cancerous prostate enlargement, which is a normal part of ageing. Conversely low levels of PSA in the bloodstream do not rule out the possibility of prostate cancer..
How is the PSA test done?
The test involves drawing blood, usually from the arm. The sample is sent to a laboratory and it may take one to two weeks for the results to come through.
When should I have my PSA levels tested?
There is still a lot of debate about whether and when men should have routine testing for prostate cancer. The American Cancer Society, for example, recommends annual PSA blood tests and digital rectal examinations starting at 50 years old, and at 45 years old for African-American men and men with a family history of prostate cancer.