personal gene tests show limited use

by Elizabeth Lopatto and John Lauerman April 2009 (Bloomberg)

Companies that sell DNA testing to pinpoint individual risks for common diseases provide little real information, says one of four commentaries featured in the New England Journal of Medicine. David Goldstein, a Duke University researcher, wrote that most common

disorders, including cancer and diabetes, involve hundreds of genes, and that many mutations may have the capacity to raise a person’s risk. That suggests the testing offered by companies now, which focuses on the few variants that have already been identified, isn’t likely to spot people at highest risk, he said. “In pointing at everything, genetics would point at nothing,” Goldstein wrote yesterday in the journal.

DeCode Genetics Inc., based in Reykjavik, Navigenics Inc., of Foster City, California, and 23andme Inc., of Mountain View, California, are among companies that test the DNA of individuals to pinpoint variants that may identify disease risk. The journal commentaries are the first public forum featuring leading genetic researchers discussing the usefulness of so-called genome-wide association studies, research that scans the DNA of thousands of people to identify mutations that may be common to certain ailments. The headline on the lead commentary asks, “Are we there yet?” The answer suggested by the authors is not quite.

Human Genome Project Researchers hoped the studies, made possible by completion of the Human Genome Project in 2003, would open new windows on why ailments such as cancer

and diabetes occur, and allow doctors to offer highly personalized treatment regimes that would focus on the underlying cause. At the same time, companies such as DeCode, Navigenics and 23andme have designed tests, costing as much as $1,000 apiece, that search through the genomes of individuals for hints disease may be hiding based on findings from

the larger research. The association studies helped make it “routine to identify common, low-risk variants” present in less than 5 percent of the population that confer only “small” risks of disease, wrote John Hardy, a researcher at the Institute of Neurology at the University College London, and Andrew Singleton, of the Laboratory of Neurogenetics in Bethesda, Maryland, in one of the four commentaries.

Genome-wide association studies haven’t explained as much of the genetic components of disease as anticipated, wrote Goldstein, director of the Center for Human Genome Variation at Duke University in Durham, North Carolina. For that reason, scientists ought to spend more time looking at rare variants that could lead to new drugs or suggest the designs for personalized prevention programs, he said. Beyond the variants for Alzheimer’s disease,

glaucoma and macular degeneration, “there are probably either no more common variants to discover, or no more that are worth discovering,” Goldstein said.

Personal tests scanning the whole genome give a lot of useless information; wouldn't there be a better solution in designing tests targeted to specific clinical conditions?