People who buy genetic tests from private companies offering to scan their entire genomes for genes linked to diseases such as Alzheimer's or breast cancer are wasting their money, according to a panel of eminent scientists.
Several companies have begun offering genome-wide scans of a person's DNA over the internet but potential customers were warned yesterday that the science is still too preliminary to provide any meaningful information.
Medical specialists also warned there was a risk of people being misled about the results of such scans that could make them either over-anxious about being labelled "high risk", or over-confident that they were at low risk of a particular disease.
"For people who are considering taking these tests, my simple message is don't," said Christine Patch, a consultant genetics counsellor at Guy's Hospital in London and a member of the Human Genetics Commission. "You are wasting your money..
"The risk is the anxiety caused but I also think there is a risk of false reassurance, for example to be told that you are at low risk of heart disease which may lead someone to carry on smoking. It's not enough to say that these tests provide useful information because actually people taking these tests believe that the information they are getting are a genetic prediction."
In the past year several companies have entered the market offering to scan a person's complete genome for up to 500,000 genetic "markers" that can indicate anything from the risk of heart disease to ethnic origins.
DecodeMe, based in Iceland, offers a screening service for about 500 which can scan for more than a dozen common diseases known to have a genetic component. Customers send cheek swabs through the post and have access to the information via a password-controlled website run by DecodeMe.
Two other companies, Navigenics, based in Silicon Valley, California, and 23andMe, set up by the wife of one of the founders of the internet giant Google, are to offer a similar service.
"These are significant companies with substantial backing. We are not talking about fringe players without any kind of presence or substance," said Stuart Hogarth of the University of Nottingham who is calling for new rules to control how these firms can operate in the UK and Europe. Next week, the Human Genetics Commission will publish a report calling on the Government to make sure the tests used by these companies go through a more rigorous assessment process.