Companies offering 'direct-to-consumer' genetic tests to predict the risk of common conditions such as heart attack and rheumatoid arthritis should provide more information to consumers about the limitations of their services, say US scientists. Their recommendations follow the finding that several tests from two such companies gave different results for the same five individuals. Genome pioneer Craig Venter and colleagues also call for more research into the predictive power of genetic markers associated with common disease, and in a wider range of ethnic groups than the European populations studied so far.
The scientists, based at the J Craig Venter Institute in San Diego and the Scripps Translational Science Institute in La Jolla, California, sent DNA samples from five people to the US genetic testing firms Navigenics and Google-backed 23andMe. Although the raw genetic data generated by the two companies was accurate, their interpretation of the results was often very different. For seven diseases, including Crohn's disease and Type 2 diabetes, their predictions agreed for only 50 per cent or less of the five individuals.
One of the reasons for the discrepancies between the companies' results was their use of different genetic variants associated with the same disease. However, the authors point out that the findings largely reflect our current incomplete knowledge of the genetic factors that play a role in the risk of future disease. 'Even this little study shows how early and primitive we are in our understanding of the human genome', Venter told Reuters news service. Scientists have uncovered more than 1000 genetic variations associated with diseases and other human traits, but it is believed many more remain to be found, and their interactions with each other and with non-genetic factors such as diet and lifestyle are still poorly understoood.
The authors make nine recommendations, including a call for companies to tell consumers exactly what proportion of the estimated genetic contribution for a disease is currently known, and to agree to use the same genetic markers in their tests. They also call upon the wider genetics community to carry out more research into how people use personal genomic data to improve health; more long term studies assessing the accuracy of predictive tests; and more genetic research in non-European populations.
Other articles in last week's Nature reviewed the successes of the 'genome-wide association' studies (GWAS) carried out to date - the large-scale projects used to identify many of the genetic variations associated with disease - and what still remains to be done to understand the genetic basis of common conditions. It is essential that the future benefits of human genetic research are not oversold, and inadequate predictive tests are not offered prematurely to consumers.
This crucial issue will be considered on Wednesday 18 November 2009 at Does Genetics Matter? Help, the annual conference of the charity that publishes BioNews, the Progress Educational Trust (PET). This one-day event will also review past successes in the care and treatment of families affected by monogenic disorders, and look at recent developments in the emerging field of epigenetics, which promises to shed light on the interplay between genetic factors and environmental influences.