Professor Nilesh Samani, British Heart Foundation chair of cardiology, says the tests are too inaccurate to help the individual.

Someone deemed high risk for a disease based on their gene test may never go on to develop the condition.

Professor Samani will talk at a human genetics meeting in York later today.

'No real value'

Many companies in the US and Europe offer gene tests for conditions such as diabetes, heart disease and cancer.

The technology responsible for this sudden surge in genetic markers – known as Genome Wide Association Studies - involves scanning the entire genome of hundreds or sometimes thousands of healthy and diseased volunteers to pinpoint key differences in the DNA likely to contribute to the disease.

Professor Samani, from the University of Leicester, questions the clinical usefulness of such tests.

"Over recent years, scientists have made incredible progress in unravelling the genetic basis of common diseases, leading to the discovery of genetic markers for a growing number of diseases.

"However, carriers of these genetic markers are typically only 20-40% more likely to develop the condition per copy..

"Even a batter of 5-10 genetic markers for the disease is unlikely to be sufficient to tell the patient whether they will actually develop the disease, when they will develop it, or whether lifestyle changes could prevent them from developing it."

And there is a danger that the tests could provide a false sense of security for some people.

"Having a 'low' risk variant of a gene doesn't mean 'no' risk," warned Professor Samani.

Science not yet strong enough

"There is no real value in testing at the moment. The prediction at the individual level is not sufficiently discriminative to tell you if you are going to get a disease or not," he said.

The Human Genetics Commission thinks there needs to be evidence that genetic tests accurately and reliably predict what they are advertised as predicting.

"They also need to be provided in the context of proper consultation where their implications can be discussed and managed," it says.

Professor Samani will be speaking at a meeting of the British Society for Human Genetics.

Although Professor Samani is sceptical about the use of genetic markers for risk prediction, he believes there are other areas where their use might be more appropriate, such as identifying individuals who could specifically benefit from preventative intervention or screening.

Professor Samani is planning projects to pinpoint genetic markers for identifying those who will benefit from taking statins to reduce their risk of heart disease.

BBC