Genetic screening is coming to the masses. While medical science has long been able to test for rare mutations that cause disorders such as Huntington’s disease or cystic fibrosis, recent discoveries have started to explain how everybody’s health is affected by DNA.

Over the past year dozens of genetic variants have been linked to a slightly raised risk of common conditions such as heart disease and diabetes. We are entering a new era of genetic medicine in which it is becoming possible to profile all people for their inherited risk of disease.

For those with deep wallets, it has already arrived. Last year two online services, deCODEme and 23andMe, were launched; for about £500 they will assess subscribers’ DNA and then calculate their risk of 20 diseases.

They have drawn criticism from many geneticists who say that the results can provide misleading and incomplete information, making few meaningful health predictions while promoting needless anxiety or false reassurance. There have also been calls for regulation of this new sector to ensure that results are scientifically accurate and that insurers or employers cannot demand their disclosure.

These are views with which I have a good degree of sympathy. But while reporting on genetic findings for The Times, I have become intrigued by what they may mean for me. Do I have the genetic variant that makes people slightly more likely to become obese? Do I have a high genetic risk of prostate cancer, or type 2 diabetes? The deCODEme service, which scans a million points in the genome at which individual DNA varies, could offer me a few answers. And my DNA would allow me to put its merits to the test.

Signing up was as simple as buying a book on Amazon: I registered on a website and paid the $985 (£495) fee by credit card. Though I had to agree to a disclaimer, accepting that the results would not constitute medical advice, there was no requirement for any sort of genetic counselling.

A few days later, my genotyping kit arrived – two cheek swabs, with which I was to collect a sample of my cells, and a prepaid envelope with which to send it for testing.

“You have been genotyped!” I was told on logging on to deCODEme’s website. I was presented with a list of 20 diseases – including Alzheimer’s, heart attacks, colon and prostate cancer, and diabetes. Before downloading my genetic profile, I reflected for a moment on what I was about to discover. Many of the diseases in front of me were life-threatening and only for some of them can the risks be lowered by lifestyle changes or drugs. I might learn that I have a high risk of Alzheimer’s or multiple sclerosis – devastating conditions that I would be unable to prevent.

Would this knowledge make me fatalistic or depressed, or consume me with fear? There could also be hazards in supposedly good news. Would a low genetic risk of diabetes or heart attacks make me more casual about healthy living? Such concerns, though, were balanced by overwhelming curiosity. Perhaps a few thousand of the 6.5 billion humans alive today have yet had the privilege of finding out so much information about the DNA that makes them unique. Here was my opportunity to become an early part of the genomic age.

I also understood that genes tell only part of the story. All these diseases are affected by environmental factors as well as by DNA, and only some of the genetic variants that contribute were even being tested. I knew that these tests would reveal probabilities, not fate.

What is more, my family history did not suggest that my genome was full of ogres. Only for one of the conditions – exfoliation glaucoma, which can cause blindness – did I know of an appreciable family history. I clicked on the link.

My eyes were drawn immediately to the column of relative risks, which show how my DNA makes me more or less susceptible to diseases than the rest of the population. Two big numbers stood out – my risk of both glaucoma and coeliac disease was 2.4 times higher than the average. Glaucoma was no great shock, given my family history.

Coeliac disease, or gluten intolerance, was more – I know of no one in my family who suffers. But while the relative risk looked high, my absolute risk is low. Coeliac disease is rare, affecting only one person in 100, so my lifetime chance of developing it is still small, at 2.4 in 100.

For the really scary diseases that dominate the mortality and morbidity statistics, the news was pretty good. My relative risks of type 2 diabetes and colon cancer were bang on average, and for prostate cancer and Alzheimer’s disease were low. I also have the “slim” variant of the FTO gene that influences obesity: my DNA provides no excuse when I put on weight.

For heart attacks, my genetic risk is very slightly elevated at 1.12 times the average. But relative risks can be misleading when they apply to very common conditions: as heart attacks are so prevalent, this was easily the highest absolute risk on my chart.

The pitfalls of interpreting this information are highlighted by my results for asthma. My relative risk was 1.45, and my lifetime risk is 18 per cent. Yet I don’t have asthma, I’m 33, and most cases are diagnosed before the age of 20. My risk is actually much lower than my genes might suggest, because the system does not adjust for age.

Most of what I have learnt is intriguing but it has not much affected the way I think about my health. Genetic influences on all these conditions work in concert with lifestyle, and there is little in my DNA profile to suggest an urgent need to modify mine.

If I had not already known of my glaucoma risk, that knowledge would have been valuable, but I am already tested for it annually. A GP could also have given me the same advice free by taking a family history.

I was impressed with the quality of the scientific information that deCODEme provided – all the variants it tests for are comprehensively referenced. With genetic testing, it is critical to tell people their absolute risk of conditions, and the website does this well. Some of the criticism of this service has been misplaced.

But I have been quite lucky with my results. I was relieved that I’m not at high risk of Alzheimer’s, but what if I had been among the 3 per cent who have a sixfold relative risk? I’m not sure I would have wanted to find out over the internet, without any counselling. The company would have referred me to a genetic counsellor, but at my own expense.

I’m also fairly well versed in genetics, and I had the benefit of discussing my results for two hours with a panel of experts (see opposite). Others will find this information bewildering, and perhaps disconcerting.

Many will approach their GPs, who have little specialist knowledge of genetics and may struggle to make sense of the data in a ten-minute consultation. There is a danger of an increase in the ranks of the worried well, creating an extra burden for the NHS.

If you are looking out of curiosity, and feel confident about intepreting the data, deCODEme offers an exciting opportunity. But if you are doing it for the sake of your health, there are better ways to spend £500.

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