Of all the genes linked to the disease so far, deCODE’s plays the largest role. More than a third of Americans carry one faulty and one normal copy of the gene; their risk of developing diabetes is 40 percent greater than those who carry two normal copies. For people with two flawed copies, inherited from both parents, the risk of diabetes is double the norm. (About 10 percent of Americans carry two bad copies.) The gene is part of the reason a family history of diabetes can signal an increased risk. But the faulty variant can also appear in thin people with no family history and no other risk factors.
The new test, by itself, tells people only part of the hand they’ve been dealt. But that knowledge alone can help them play the rest of their cards wisely–eating healthier, exercising more and, in extreme cases, taking medications such as metformin that control blood-sugar levels and may ward off diabetes. Losing weight and exercising a few times a week can drastically reduce patients’ risks, even if they’re unlucky enough to have two flawed copies of the gene. “It’s often difficult to get people to lose weight if they haven’t developed diabetes already,” says deCODE CEO Kari Stefansson. “Having this insight into their future personal risk can give them the motivation to deal with it in advance.” For an extra boost of motivation, the new test’s $500 sticker price includes counseling sessions with doctors to help patients plan for the worst and, hopefully, avoid it.
Still, the test has some detractors. Larry Deeb, president of medicine and science for the American Diabetes Association, says he worries that patients might view a negative result as permission to live carelessly. “The test isn’t black or white. Just because you don’t have the gene, that doesn’t mean you have zero risk,” says Deeb. “So we don’t want to be telling people that if they test negative, they can just sit on the couch and not worry. They’re still not off scot-free.”
Like all genetic testing, the test also raises the specter of discrimination by health-insurance companies and employers. Insurers are already reluctant to take on patients who have been diagnosed with diabetes. They might go further and start rejecting people who score positive for the gene but have not yet developed the disease. Deeb says that privacy laws can address some of those concerns–patients can simply request that doctors not reveal their status to insurers. And Stefansson notes that “no one is forcing people to take a test like this.” In a few years, he adds, people worried about their risk might also be able to sidestep doctors altogether by using a possible home version of the test. (The current test requires blood to be shipped from docs’ offices to deCODE’s labs.)
The bigger problem with insurers, says Deeb, will be getting them to pay for the test in the first place. It may be hard for patients who don’t already have the other risk factors–arguably those who would most need to learn about their unexpected genetic bad luck–to convince them the test is worth the money. But Deeb adds that a suite of tests, aimed not just at one gene but at all those known to influence diabetes, would be more useful and more appealing to insurers. With researchers discovering more and more about how diabetes develops, those tests may also become available in just a few years.
