"People will need to be prepared for the fact that these tests are so new that the physician may have limited ideas of what to make of it and what to do with it," says genetic counselor Barbara Biesecker of the National Human Genome Research Institute in Bethesda, Md.
To test or not? So should a person who is free of ailments consider getting his or her genome mapped now, or as soon as the procedure hits the $1,000 mark? The answer appears to be a definite maybe. For some rare diseases like Huntington's, a single, easy-to-spot mutation means that an individual will inevitably develop the fatal illness. Similarly, certain other gene mutations confer a 60 percent risk that a woman will develop ovarian or breast cancer in her lifetime, five times that of women who lack the flaw. Knowing this, the woman could undergo early screenings for these cancers or even opt for elective surgery before the disease gains a foothold.
Most mutations, though, aren't of the all-or-nothing type. Instead, they confer only a small increased risk of developing a particular disease. People should keep in mind that such test results have limited value, says Biesecker. Individuals also may not want to know their risk for diseases they can do nothing about. "I'm just really worried about people who don't know what they're signing up for and what information they could get back," she says.
Mapping a subset of the genome, though, can be of enormous help in determining which drugs a person may be acutely sensitive to, or not respond to, because of the way the body metabolizes certain compounds. Some of these drug-related genetic tests (though not a map of the entire genome) are covered by health insurance. For example, before prescribing the blood thinner warfarin, used to treat some types of stroke and heart disease, many doctors do genetic testing to determine the optimum dosage. Some breast cancer patients are similarly tested to see how much of a particular protein, associated with an aggressive form of the disease, their genes produce. A drug targeting that protein may then become part of the treatment. "For most cancers, though there is not a requirement for a genetic test, it is the obvious thing to do," says Snyder.
But when it comes to getting the entire genome mapped, even researchers intimately involved with the testing have declined. As Biesecker says: "Perhaps I'm too much of a cynic, but there's not too many things you can benefit from knowing ahead of time before you start having symptoms."
Jeffery Schloss, program director for technology development coordination at the National Human Genome Research Institute, adds that most people can glean better information from a family history—at least for now. But Harvard Medical School geneticist George Church disagrees. He is director of the Personal Genome Project, which aims to map the genomes of 100,000 volunteers willing to make public their genetic sequences, along with medical and health records. Church notes that new genetic mutations or combinations occur all the time and may not be apparent in family histories.
The process of getting your genome mapped is relatively simple: A blood sample taken in a doctor's office is mailed unrefrigerated to one of a handful of genome sequencing companies, which chemically extract and dry the genetic material into a tiny pellet. Within weeks, the genetic code contained in the pellet is cracked open using electrical or chemical techniques and a report is sent to the designated doctor, who can interpret, for example, what dosage of a particular drug to administer. The code may also be recorded on a flash drive.
The ease of the procedure and its dropping cost are likely to attract others to have their genomes mapped. Though experts still debate the benefits, improvements in interpreting people's genetic codes will likely make such testing an increasingly valuable tool in the delivery of more individualized and effective medical treatments.