Personalised health tests that screen thousands of genes for versions that influence disease are inaccurate and offer little, if any, benefit to consumers, scientists claimed on Monday.
An investigation into the services found they gave wildly different results, and in some cases arrived at medical predictions that were no better than flipping a coin.
The findings of the Dutch study will bolster calls for tighter regulations around personalised genetics tests which can cost more than £500. Critics claim the tests are a waste of money that could mislead people about their future health.
According to the group at Erasmus University medical centre in Rotterdam, tests from rival companies predicted conflicting risks for some diseases, often because they disagreed on how common the conditions were in the general population.
Another flaw was that the tests looked only at genetic factors, whereas many diseases are governed more by lifestyle and other environmental factors.
In the study, researchers used a computer to simulate genetic information for 100,000 typical people. They then used formulas from two of the largest genetic testing companies, deCODEme and 23andMe, to predict the risk of eight medical conditions, including heart attack, prostate cancer, coeliac disease, an eye disease known as age-related macular degeneration and diabetes.