DNA disease tests should come with warning label.
Possessing the complete catalog of all human genes--the genome--has a lot of scientific value. It enables studies that illuminate aspects of evolution through comparison with genomes of other species. It facilitates scientific studies of the roles various genes play in normal biological activities. And it even aids the effort to understand the relationships between certain gene variants and human diseases.
It's not so good, though, at forecasting what specific diseases any individual human is likely to suffer from.
A new mathematical analysis, based on health reports from more than 50,000 pairs of identical twins, finds that analyzing your genome would help predict your risk for only a very few diseases, as Tina Hesman Saey reports (Page 11). She cites one scientist's view that you're better off weighing a patient and asking about smoking habits.
All this should come as no great surprise. Even though there has been a lot of hype over the years about the medical benefits of cataloging the genome--and companies sell DNA testing services that supposedly identify medical risks--sober analyses have repeatedly noted that the science doesn't support some of the more extravagant claims. Nearly three years ago, for instance, readers of Science News encountered a feature article on tests people could buy to have their DNA analyzed (SN: 7/4/09, p. 15). As the feature noted, test-buyers received reports linking specific features in their DNA to elevated or reduced risks of various diseases. "But the genetic report cards these amateurs are reading may not be as definitive as they assume," the article pointed out. "Despite progress in linking genetic differences with disease risk and other traits, the predictive power of these links has fallen short of expectations."
It's not that such tests have no value at all. Genetic testing can identify elevated risks for a few diseases. And as genetic knowledge improves, and better medical interventions are devised, and the interactions of genes with environmental effects are better understood, DNA testing will no doubt play a role in providing better, and more personalized, medical treatment. But that will come only as exaggerated expectations are tempered by solid evidence. And sorting the hype from the scientific substance is what both good medical practice and good science journalism are all about.
--Tom Siegfried, Editor in Chief