There are lots of medical screening
tests available and screening is big business, but which of these tests
are really useful and what are the drawbacks? Michael Mosley decided to
find out by looking at the evidence and trying a whole battery of them.
I
began with heart disease, as it is the largest cause of premature death
in the UK. The basic tests are free, on the NHS, and relatively
straightforward.
First I had some blood taken to measure things
like cholesterol, then I went to visit my GP, Dr Sally Jenkins, who
measured my height, weight and blood pressure.
She fed all this data into an online calculator called qrisk
and the answer came back that I had a 10% risk of having a heart attack
or stroke over the next 10 years. This doesn't sound great but it is
slightly better than average for someone of my age. Nonetheless, Sally
told me, the guidelines suggest I should go on a statin.
I have an
ambivalent attitude to statins. On the one hand statins can reduce your
risk of death if you have heart disease, but the benefits for the
apparently healthy are less clear. Statins also have side effects, like
increased risk of type 2 diabetes.
Not sure what to do, I went off for another test - this
one a cardiac CT scan. In a private clinic they can cost between £600
and £1,000 and involve a low dose of radiation.
This test consists
of lying in a machine, being injected with a contrast dye, then having a
series of low dose X-rays. The machine shows up your coronary arteries
in great detail, so a doctor can see if you have partial blockage.
Originally
developed as a diagnostic tool for people with symptoms of heart
disease, this technology is now being used to screen people, but largely
on a private basis.
After I had been through the machine,
cardiologist Dr Duncan Dymond took a look at my scans. He started by
pointing out an ominous dark shadow on one of the main coronary
arteries, the proximal left anterior descending (LAD).
"The reason it's dark," he says, "is because that is a deposit of soft cholesterol-rich plaque on the wall of the artery." "That's bad?" I ask anxiously.
"Yes,"
he replies, "I don't want to sound overdramatic but those are the ones
which are dangerous because of their propensity, unpredictably, to cause
heart attacks in someone who's been completely well, free of symptoms,
living a normal life. You go out in the morning to work and don't come
home."
For this reason they are known in the trade as "widow makers".
He
couldn't tell me the chances of that happening, "if we could that it
would be Star Trek medicine" but he did advise me to take a statin,
"because soft plaques [treated] with statins metaphorically have the
cholesterol sucked out of them".
I'd gone in quite cheerful and
come out with the words "widow maker" rattling around in my brain. And
that's the problem with some of these private tests - they may not give
you any more detail on the risk of heart disease than the simple NHS
test, and they may leave you a lot more worried.
The second most
likely disease to kill you is cancer, but screening for cancer is
controversial, with many critics claiming that it can do more harm than
good.
Breast cancer screening is available via the National Breast Cancer Screening Programme.
It is currently offered to all women between the ages of 50 and 70, though this will be extended to 73 by next year. The Marmot report,
which looked at the evidence of effectiveness of this programme,
concluded that the breast cancer screening programme saves 1,400 lives a
year.
The Nordic Cochrane Centre in Copenhagen, a well-respected international collaboration of scientists and institutions, disagrees.
They
say that because we have better treatments for breast cancer the case
for mammography has been undermined and that recent studies "show very
little or no reduction in the incidence of advanced cancers with
screening".
Mammogram, coloured X-ray
Dr Iona Heath, the former
president of the Royal College of GPs, a long time critic, says she
would not choose screening. "My personal decision is to wait until I get
a breast lump and then get the best treatment I can get."
Dr
Robin Wilson, chair of the UK's Advisory Board of Breast Screening,
believes screening saves lives but also acknowledges there are risks.
"Women
need to be aware of what the risks are and how they balance out against
the benefits in order to make an informed choice - what we in the
medical profession need to do is get better at finding out which of the
cancers we don't need to treat."
Prostate cancer kills 10,000 men
every year in the UK but screening is even more controversial than
breast cancer screening. This is because of the well-known inaccuracies
of the PSA (prostate specific antigen) test. When I was at medical
school we were told that PSA stood for Promoting Stress and Anxiety.
As with breast cancer, the problem is you don't know which of the tumours you detect will grow aggressively, and which won't.
There is no national screening programme, but you can get more information from Public Health England.
If
a tumour is detected then you have a range of options, from surgery and
radiotherapy (side effects include incontinence and impotence) to
watchful waiting.
As the name implies, rather than intervene
straight away, your doctor will wait to see if the tumour is aggressive
and fast growing or relatively benign.
Dr Vincent Gnanapragasam,
who runs a watchful waiting programme at Addenbrokes hospital in
Cambridge, tells me: "There was a study which took men with all kinds of
prostate cancer and randomised them to having nothing done or radical
surgery and at the end of 10 years there was actually no difference in
the overall survival. Most importantly the men with low risk cancer had
absolutely no evidence of benefit from radical treatment."
The one test that all the experts I talked to agreed was worth having and they would have themselves is the one for detecting bowel cancer. It's not the most glamorous of tests but it could save your life. Horizon, Should I Test My Health, is broadcast on BBC Two at 20:00 on Wednesday 12 August. Is there a problem with breast cancer screening?
The Marmot review concluded that for
every breast cancer death prevented by screening, three women are
overdiagnosed and offered unnecessary treatment.
A study published in June 2015 by an
international team of scientists, led by the WHO's cancer agency,
concluded that breast cancer screening saves lives.
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