Whole-Genome Scans Not Ready for Widespread Use?
Tests are promising but not yet reliable enough, experts say
"We have to be honest about what we can reasonably expect this technology to do," Dewey said.
In particular, his team found that two commercially available whole-genome tests are not yet accurate enough to rely on for routine use. The tests were not able to reliably detect all variations in 7 percent to 16 percent of 56 genes that are known to be associated with disease risks.
"There's still a gap between where we are and what would be clinically acceptable," Dewey said.
Even if the sequencing technology were perfect, that would still leave the question of what to do with all the genetic information, said Dr. William Feero, of Maine Dartmouth Family Medicine Residency, in Augusta.
"Trying to determine what's meaningful is quite challenging," said Feero, who wrote an editorial published with the study.
Much of what's known about the genetic underpinnings of disease is confined to what's called the "exome" -- the genes that make the proteins that run your body. But the exome accounts for only about 1 percent of the entire genome. The vast sea of genetic material beyond that was once thought of as "junk DNA," Feero said.
Scientists have known for a while that's not true -- that DNA has a number of important jobs, including regulating the protein-making genes of the exome. But Feero and Dewey both said much more remains to be learned about DNA variations and disease risk.
Even when there is strong evidence linking a gene variant to health consequences, it might not be clear what to do about it. With the BRCA1 mutation, the risks are clear and women have options for reducing those risks, Feero said.
"For a lot of [DNA] variations, there's little information on what to do about it," he said.
One of the fears about widespread genetic testing is that doctors will be spurred to order a lot of expensive, possibly unnecessary follow-up tests or treatments. In another part of their study, Dewey and his colleagues gave the study participants' results to five doctors to see what they would recommend as a follow-up.
Overall, they recommended one to three tests or referrals for each participant, at a cost of about $350 to $800. "That's reassuring, to some degree," Dewey said, since his team actually expected a much higher price tag.
The caveat is that the results are based on five doctors -- two of whom were medical geneticists. No one knows, Feero said, what the average doctor in the real world would do.
Still, both he and Dewey said whole-genome sequencing holds great promise. Feero predicted that it will at first be used in limited circumstances -- such as helping to diagnose a patient with a chronic condition that is eluding traditional diagnostic methods.
Meanwhile, prices continue to fall. Biotech firm Illumina, for example, advertises its current genome-sequencing services at anywhere from $5,000 to $17,500, depending on the specifics. But in January, the company unveiled a new technology it says will bring the cost of sequencing a whole genome to around $1,000.