Image copyright Fleur Bone

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.

Find out more Horizon, Should I Test My Health, is broadcast on BBC Two at 20:00 on Wednesday 12 August.

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."

Image copyright Fleur Bone

"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".

Image copyright Science Photo Library Image caption 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?

Image copyright Getty Images

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.

Why isn't breast cancer screening totally reliable?

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