Image: DNA
Adrian Neal
Once the exclusive domain of doctors and genetic counselors, DNA analysis is now a do-it-yourself proposition. But most experts say it's too early to make strong links between tiny genetic variants and the development of diseases.
updated 4/9/2009 8:29:46 AM ET 2009-04-09T12:29:46

Anna Peterson is only 27, but she's already watched her mother and her aunt develop breast cancer. She also saw her grandmother's eyesight fail from macular degeneration. So Peterson, a graduate student in Ottawa, Ontario, took her health care into her own hands and did what millions of others of all ages are doing: She opted for an at-home genetic test.

When the results from the $985 test from deCODEme arrived in her e-mail, Peterson felt relief learning that she didn't have an elevated genetic risk for macular degeneration.

Yet the test did show a slightly elevated risk for the more common forms of breast cancer. The results, Peterson says, empowered her to make healthier choices. Together with her physician, she'll use that information to advocate for earlier screening for breast cancer — and possibly start getting mammograms at age 30.

“Prevention starts with knowing the odds,” says Peterson. “I now have the opportunity to make lifestyle changes in my 20s, rather than in my 60s.”

Welcome to the brave new world of genetic testing.

Once the exclusive domain of doctors and genetic counselors, DNA analysis is now a do-it-yourself proposition, with several dozen companies marketing tests directly to consumers, claiming that they will allow you to understand your genetic profile. The process is surprisingly simple: Buy a test online, swab the inside of your cheek or spit into a test tube to collect a DNA sample, and then mail it to the company. In return, you'll receive personalized medical information that purportedly allows you to combat disease by making informed choices about your health. Bolstering that promise is new research that shows you can actually turn off genes that promote certain diseases by improving your diet and better managing stress.

People clearly approve of genetic testing. In a recent Prevention.com poll, 87 percent of respondents said they'd want to know which inherited diseases they're at high risk of developing. Moreover, 54 percent said they'd be likely to have a genetic test even if there was no known treatment or way to prevent the disease.

Not ready for prime time
Plenty of companies are eager to meet this demand, selling at-home tests that range in cost from hundreds to thousands of dollars. Some offer tests that have long been available through doctors and genetic counselors — for instance, those that check for BRCA 1 or 2, the genes linked to a small percentage of inherited cases of breast cancer. Newer versions look at your SNPs (pronounced snips, short for “single nucleotide polymorphisms”), the slight variations within DNA that can account for differences in appearance and how we develop diseases.

The companies don't predict that you're going to get, say, cancer or macular degeneration. Rather, you get back a report showing the risk you run, compared with the average person.

One of the newest entrants into the at-home arena, Navigenics, recently launched its $2,500 Health Compass test, which looks for markers associated with 23 common conditions — including diabetes, prostate cancer, and Alzheimer's disease — that are "actionable," or able to be prevented or detected early. For an additional $250 per year, subscribers receive personalized updates when relevant genetic research — for instance, the discovery of new SNPs — changes their health outlook.

Health-conscious consumers are clearly enamored with these high-tech tests — they're expected to spend an estimated $6 billion to have their DNA decoded over the next 5 years. But while the business of do-it-yourself genetic testing is booming, experts say this new frontier of medicine isn't ready for prime time. They worry that the field is insufficiently regulated, not all of the tests are reliable, and the information garnered is incomplete and possibly misleading.

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“Some tests lack adequate scientific evidence to support their use, and the lack of regulation means there's no way for consumers to separate the good from the bad,” says Gail Javitt, law and public policy director for the Genetics and Public Policy Center at Johns Hopkins University.

The risks of peering into your medical future
Despite an explosion in the discovery of SNPs, most experts say it's too early to make strong links between these tiny genetic variants and the development of diseases.

That's because the role played by a single mutation is believed to be modest. Rather, it's the interaction between multiple SNPs and factors like diet, exercise, and weight that predispose you to disease — indeed, studies show that lifestyle accounts for about 70 percent of our susceptibility to health problems such as diabetes, heart disease, and some types of cancer.

As a result, “these tests can't accurately predict the risk of developing these complex diseases at the moment,” says David Hunter, MD, ScD, professor of epidemiology and nutrition at the Harvard School of Public Health.

Likewise, some tests that claim to gauge your risk of diseases such as depression examine single genes that explain only a small part of the predisposition to those illnesses.

Critics also note that test results can be tough to interpret, making it difficult to know when and if you should take action.

A Navigenics test told Robert C. Green, MD, PhD, MPH, a professor of neurology, genetics, and epidemiology at Boston University Schools of Medicine and Public Health, that he had a 20 percent above-average risk of developing multiple sclerosis. But the average risk is 0.3 percent, and his was just 0.5 percent. These are both very low risks (3 out of every 1,000 versus 5 out of every 1,000, respectively), yet the results were highlighted in orange, indicating an elevated risk. Green, a geneticist, understood his real risk, but the average person might not, causing needless worry.

And consider the flip side: that someone who tests negative for a gene or is told she's at low risk for developing a dreaded disease becomes less motivated to lead a healthy lifestyle.

David Katz, MD, MPH, director of the Prevention Research Center at Yale University School of Medicine, points to a study on premenopausal women given a range of tests to determine their risks of developing heart disease.

Half saw scans of their coronary arteries, which were surprisingly healthy. But despite other risks revealed from triglyceride and blood glucose levels, the group that saw its healthy scans did less to follow recommendations to prevent heart disease.

“We don't want a single test talking people out of taking care of themselves, and this study suggests that can happen,” says Katz.

Test results: helpful or confusing?
Proponents of mail-order genetic testing claim it has just the opposite effect and instead helps people gain new insights that sometimes dramatically boost their health.

David Agus, MD, an oncologist and cancer researcher at the University of Southern California, started Navigenics with the hope that people would get tested, discuss results with their physicians, and use the information to seek an earlier diagnosis or delay the onset — or prevent — certain conditions altogether.

That's precisely what happened in the case of Mari Baker, the company's CEO. When her results revealed a 5-times-greater risk of celiac disease, follow-up testing ordered by her physician confirmed she has the digestive disease, which is caused by an intolerance to gluten, a protein in wheat, rye, and barley. The diagnosis explained the GI problems Baker, 44, suffered over the years. She immediately changed her diet and stocked her kitchen with gluten-free pasta, bread, and beer.

“Feeling a little bit better every day for the next 20 years is pretty important,” she says.

Unfortunately, test results aren't always so clear-cut and accurate.

Mike Spear, the communications director for a genomic research nonprofit in Alberta, took tests from deCODEme and 23andMe and received some conflicting findings. For instance, the deCODEme test showed a higher-than-average risk for MS, but the 23andMe test said his risk was no higher than that of the average person. The test from deCODEme also had a big check mark next to “male pattern baldness,” while the 23andMe test said he was on par with the rest of the population. (Spear, who's 55, still has plenty of hair.)

Most surprisingly, both tests told Spear that his risk of asthma was no different from the average person's — even though he already suffers from the disease. His impression: “I'd be careful about basing your life around genetic test results.”

Although new genetic research emerges every day, scientists haven't discovered all the genetic variants — or all the SNPs — for common diseases. Green, 54, took two genetic tests, one from 23andMe and the other from Navigenics, and both told him that he had an average risk of cardiac disease. Yet he had undergone triple bypass heart surgery the previous year.

As a runner who is not overweight, doesn't smoke, and has low cholesterol, Green suspects there's a genetic cause for his tendency toward blocked arteries — and he chalks up the discrepancy in his test results to the fact that more research is needed to fully understand the genetic causes of cardiac disease. Another reason to think twice about these tests: The industry is a virtual free-for-all.

‘DNA isn't destiny’
No single government agency watches the labs performing the tests to ensure that the science behind the tests is even real. Currently, the FDA reviews most other home-use medical tests for safety and effectiveness, but at-home genetic tests don't fall under the agency's territory. Pending legislation would require makers of direct-to-consumer genetic tests to prove that their tests are accurate and properly performed. But right now, "the public's best approach is buyer beware," says Kathy Hudson, PhD, founder and director of the Genetics and Public Policy Center at Johns Hopkins.

Despite these warnings, experts predict that people will be very tempted by the chance to peek into the genetic crystal ball. If you're one of them, heed Katz's reminder: "DNA isn't destiny." And be aware that when it comes to the lifestyle choices that are the greatest predictors of health, your future is in your hands.

Copyright© 2012 Rodale Inc.All rights reserved. No reproduction, transmission or display is permitted without the written permissions of Rodale Inc.

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