Unproven genetic tests may create false sense of security or unnecessary anxiety

Clinical trials are urgently needed to validate the increasing number of experimental genetic tests available for assessing an individual's risk of developing serious common diseases, such as heart disease, stroke, diabetes and cancer, Professor Nilesh Samani, British Heart Foundation Chair of Cardiology at the University of Leicester, told delegates at the BSHG annual conference today. Given that many of these tests have not yet undergone rigorous testing, there is a danger that they may create unnecessary anxiety in some individuals or create a false sense of security in others, warns Samani.

'Even a battery 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. On the other hand, since having a 'low' risk variant of a gene doesn't mean 'no' risk, there is a real danger that some patients might gain a false sense of security,' he said. The technology responsible for this sudden surge in genetic markers - known as Genome Wide Association Studies (GWAS) - 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.

'Over recent years, scientists have made incredible progress in unravelling the genetic basis of many 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, raising questions over the clinical usefulness of such tests.'

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. He said: 'The genetic markers may help to identify individuals who may specifically benefit from preventative intervention or screening although this needs to be tested in proper trials to assess both efficacy and cost. Better understanding of the genetic basis of many common diseases is also helping to re-classify several diseases and to provide new drug targets.'

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.