The reliability of test results is questionable. People are assessed for often complex, multi-gene conditions like diabetes, heart disease, Parkinson's disease and some cancers. Many of these diseases are influenced by a person's lifestyle and environment as well as their genetics. There is insufficient evidence to substantiate claims these tests can establish accurate and reliable indications of a person's risk of developing these diseases.
The results people receive from these tests can be complicated. It is difficult for anyone without specialist knowledge to interpret what they mean, particularly without the advice of a genetic counsellor or doctor. For example, what do you do with the information that you have a six percent above average risk of developing Alzheimer's disease? Is this cause for concern? Does this cause unnecessary anxiety because there is nothing you can do about getting Alzheimer's? Should you inform family members, even though you may never develop the condition?
The idea tests enable people to 'take control' of their health is questionable too. People might feel they can change their lifestyles or seek advance treatments following these tests for the benefit of their future health. In reality, the tests are unlikely to reveal disease risks that can be significantly changed by behaviour, other than prompting obvious healthy lifestyle choices.
What should be done? We do not recommend direct-to-consumer testing should be banned - that would be a disproportionate step, given the lack of available evidence at this time about the harms testing may cause. We would like to see companies giving clearer and more prominent information to consumers before they buy these tests. Companies' information should also explain more about the limitations of test results and the fact they may require interpretation by a doctor or geneticist. The possible implications of taking a test should also be explained more, such as whether to tell family members who may also be affected by the results.
Government-provided health websites should also give information about the risks and benefits associated with such tests, including whether people may have to inform insurance companies of their results. Doctors, too, should be trained on how to advise people who considering taking tests and how to make referral decisions based on the test results.
It is hard to predict how fast our knowledge of the relationship between genetics and health will develop in future. But finding out about personal genetic information is likely to become an affordable possibility for more and more people as the cost of sequencing DNA continues to fall. That is why we need more research on the impact of tests. We also need better information for potential users to help them better understand test implications and limitations.