Genetic testing you can order online

Genetic testing, billed as a way to identify your health risks, is as easy as shopping online. Before you sign up, take a critical look at what you're buying.

All your relatives on your father's side have high blood pressure. Your maternal grandmother lost most of her eyesight by her eightieth birthday — and your mother and uncle have serious vision problems, too.

For now, your own health is fine. But what about the future?

Genetic testing may look like the answer. You've seen genetic testing services advertised online as a way to assess your risk of getting a wide range of medical conditions. Just mail in a saliva sample or scraping from inside your cheek, along with a fee of about $1,000, and soon you'll be online, browsing your own DNA.

Armed with your risk profile from genetic testing, you could take action now to avoid the health problems that plague Mom and Dad. So why not sign on?

Here's why not, at least for now. Although commercial genetic tests offer tantalizing glimpses into your hereditary makeup, the information they provide isn't all that useful for avoiding disease — and may even cause more harm than good. Find out what home genetic testing can and can’t do for you and what the future might hold.

Analyzing "Snips" of DNA

Molecular genetic testing involves examining a person's DNA, the chemical database that carries instructions for making all the proteins your cells need to carry out your body's functions. Genes are the segments of DNA that carry a particular set of instructions. There are approximately 30,000 genes that make up the DNA strands in each of your cells, your genome.

Genetic tests have been used for years to identify specific genetic changes known to be associated with a particular disease. Testing laboratories currently perform more than 1,100 different genetic tests. These tests serve many purposes, from screening newborn babies for hereditary disorders to diagnosing inherited cancer syndromes.

What's different about the new commercial genetic tests? They use DNA microarray technology to evaluate the genome for hundreds of thousands of points of difference in a person's DNA rather than just a few specific genes. These tiny differences in gene sequence are known as single nucleotide polymorphisms, or SNPs, pronounced "snips."

Researchers have identified over a million SNPs and correlated some of them to disease risks, physical and other traits. And a whole category of SNPs, useful for geneaologists and anthropologists, holds information about where your ancestors came from. On the other hand, the clinical significance of many SNPS is not known.

Limitations of genetic testing

The genetic tests you can order on your own don't tell you whether you have or will get a particular disease. They can only give you your estimated odds of developing each one of a number of common diseases — and only to the extent that the presence or absence of a few SNPs tells the whole story about your risk. Most of the time, individual risk is much more complicated than that.

Many common diseases, including heart disease, cancer and diabetes, have complex genetic underpinnings — they don't stem from a single altered gene or SNP that can easily be identified. Rather, they involve interplay between multiple genes, as well as environmental factors.

Genetic tests based on SNPs assess only a limited number of gene variants associated with any given disease. But for most diseases, researchers are still in the early stages of identifying the full list of gene variants that may make a person susceptible. In other words, if you have a gene profile that's linked with a higher risk of, say, osteoporosis, it doesn't mean you'll actually get this disease. Equally important, not having that genetic susceptibility profile offers no guarantee that you won't get the disease.

What's more, SNPs account for a relatively small part of the genetic variation among individuals. There are other genomic variations, not detected by microarray technology, that may have a greater effect on disease risk than any single SNP.

Got questions? Too bad

If you order a genetic test online or through the mail, you may be on your own when it's time to interpret the results. The information you receive can be nearly impossible to put in perspective without the ongoing help of a doctor or genetic counselor. Even with the assistance of a medical professional, your questions may be unanswered due to the limited knowledge available regarding risk assessment based on these test results.

In a clinical setting, though, genetic testing always includes a consultation with a genetic counselor. Your genetic counselor will help you consider the emotional aspects of genetic testing and understand what it may — or may not — tell you. It's important to review these considerations prior to testing to assure the testing you are ordering will provide the information you want.

Quality control is another potential problem with direct-to-consumer genetic testing. While researchers say that most commercial labs perform high-quality testing, the federal government provides very limited regulation and oversight of direct-to-consumer DNA tests. Without reliable quality-control monitoring and testing, it's hard to know how valid a commercial genetic test is.

You're high-risk, but what can you do?

Even if your computer-generated genetic profile could report your disease risk in a meaningful way, how would that knowledge affect you? What could you do about it if you knew you had a higher risk of a certain disease?

You don't need to spend hundreds of dollars on genetic testing to tell you to quit smoking, eat more fruits and vegetables and get off the couch. Little research has been done to determine if people with a genotype that predisposes them to certain diseases can benefit from more frequent screening or more aggressive treatment earlier in life. Finding out you face a higher than average risk of cancer or another disease can also cause anxiety and fear.

On the other hand, people who test negative for a particular disease risk might feel a false sense of reassurance. They might be less motivated to take steps to prevent the disease, even though there's no guarantee they won't get it.

Promise for the future

The field of genetics is rapidly expanding, with exciting new discoveries reported every week. So when will all this research produce a test that will help regular people? It already has, for specific circumstances. For example, doctors are now using tests that identify genes affecting your body's response to different drugs. Results from these tests are already refining decisions about drug therapy.

Likewise, tests are available to predict whether particular drugs will work as intended when you take them. A medication that effectively treats one person's depression may not be effective treatment for another person — another difference that can sometimes be predicted by genetic testing.

Many scientists anticipate a revolution in personalized medicine based on individual "genomic profiles." Better-informed patients will become navigators of their own health, with higher odds of disease prevention. Doctors will detect diseases earlier, before symptoms develop, and offer more tailored treatments.

But broader applications for genetic testing are still a few years away. Until more is known about genetic variations and the information is proven truly useful, you're better off using simpler tools to evaluate your disease risk, such as your family health history and regular screening tests. The same things you do to reduce your risk of heart disease — maintain a healthy weight, exercise regularly, limit fats and cholesterol, eat more fruits and vegetables — will also help you prevent type 2 diabetes and some types of cancer. These healthy lifestyle habits will help lower your risk of many chronic illnesses, whether or not your genes make you more susceptible.