Carcinoembryonic Antigen (CEA) Blood Test
In the UK, we screen for many different conditions. This starts before we are even born when foetuses are screened for conditions such as Down’s syndrome then, in the new born period, babies are screened for metabolic diseases and hearing problems, school children are screened for colour blindness, and in adulthood we are screened for breast cancer, cervical cancer, and bowel cancer.
But we don’t widely screen for prostate cancer despite the existence of a simple blood test that can alert us to the possibility of the disease.
Prostate Specific Antigen (PSA) is undoubtedly a valuable test, but it is far from perfect. Its use as a universal screening test remains controversial and, in the UK, the decision has been taken not to offer it in this way. Instead, it is currently offered to men over 50 who request it and have been made aware of how it is best used.
PSA is a protein produced by both healthy prostate cells and prostate cancer cells. It is normal to have some PSA circulating in the blood, but a raised reading may suggest a problem with the prostate. Whilst this problem may be prostate cancer, it may be from something more innocent such as prostatitis (infection of the prostate) or simply an enlarged prostate. Your level of PSA can even rise after vigorous exercises, sexual activity, or because of a urine infection. This means that we get a lot of ‘false positives’ – a raised PSA when there is actually no cancer.
A false positive can cause a lot of anxiety but may also result in unnecessary investigation which can include a prostate biopsy which is invasive and carries its own risks.
It is also possible to have a ‘false negative’ – a normal PSA when there actually is prostate cancer. One study suggested that as many as 1 in 7 men with prostate cancer had a normal PSA.
Whilst the above may sound quite negative, PSA remains a useful test. PSA is capable of detecting prostate cancer before symptoms have even started, particularly if it is a more aggressive type of cancer. This can allow treatment to start early which may lead to better long term outcomes.
The key is to recognise the limitations of the test and use it in correlation with your symptoms and risk factors.
Symptoms of prostate cancer include getting up lots at night to pass urine, difficulty initiating your urine flow, and feeling that your bladder is not emptying properly. Because of the risk of a false positive PSA, if you have these symptoms, you should see a doctor about them even if the PSA test is normal.
However, if you have no symptoms and you have a normal PSA, then you can be quite confident that there is no problem.
Risk factors for prostate cancer include getting older, being of African or Afro-Caribbean heritage, having a family history of prostate cancer, or having a family history of inherited breast or ovarian cancer. If you have one or more of these risk factors but have no symptoms, you might want to have a PSA check so that any potential problem is identified early.
So, PSA is best used in people with no symptoms, who are worried about their risk factors and want the best chance to detect prostate cancer early. If you already have symptoms, or you have a negative test and then develop symptoms, then it is best to discuss this with your doctor.
Remember, if you decide to take a PSA test, avoid sexual activity and vigorous exercise for 48 hours before the test, and don’t take the test if you think you may have a urinary tract infection. This will help to ensure you get the most accurate result.