Published: September, 2010

You send in a sample and get your results online. But is it worth the price?

All disease is, to some degree, genetic. From cancer to the common cold, almost every human malady known to humankind has something to do with genes the stretches of DNA containing instructions for making the proteins that govern how our bodies are built and how they function. Your genes influence your risk for degenerative disorders the innumerable conditions from osteoporosis to Alzheimer's disease in which structure, function, or both deteriorate. They also influence allergic reactions, your ability to fend off infection, how you process nutrients and drugs, and even your susceptibility to accidents.

Trading on that knowledge and aided by technological advances that have improved the rate and accuracy of gene identification, a growing number of companies are marketing genetic testing kits directly to consumers. Their promotional materials promise to guide you to a healthier life by predicting your unique risk for developing scores of diseases and telling you how to prevent them.

The promise is enticing. Most of what we know about prevention and treatment is based on studies involving large numbers of people. Yet even the most successful regimens or therapies don't work for everyone. Genetic testing suggests the possibility of an approach to health care in which risk reduction and treatment are individually tailored. But buyer beware: while most scientists agree that the age of personalized medicine is on the horizon, many doubt that it's as close as the test-kit promotions would have you believe.

The Human Genome Project, completed in 2003, revealed just how much individual variation there is. Researchers worked out the order (or sequence) of the three billion DNA bases (chemical building blocks) that constitute the human genome (the complete set of human DNA). Although it's about 99% the same in all people, it still varies at more than 10 million DNA bases. That variation explains, in part, our varying degrees of risk for certain diseases.

In medical settings, genetic tests have been used to identify variations that cause serious health conditions. These tests are usually reserved for people known to be at risk for a specific disease because it runs in families. For example, couples planning a pregnancy may be tested to determine whether they carry the gene for Tay-Sachs disease. Women with close relatives who developed breast cancer early in life may want to know if they carry one of the high-risk BRCA genes. Because the results of such tests can alter lives, they are best administered only after individuals have been counseled on the risks, benefits, and limits of testing and have given informed consent. The results are confidential, and their implications should be explained to patients by genetic counselors.

Clinicians can also use genetic testing to help them select more effective drug treatments. For example, postmenopausal women with breast cancer for whom tamoxifen may be an option are sometimes tested to see if they have a gene variant that renders tamoxifen less effective; if they do, they can be prescribed a drug that works differently. Another genetic test may help determine whether patients at risk for blood clotting will benefit more from clopidogrel (Plavix) or from another drug such as prasugrel (Effient).

Direct-to-consumer genetic testing kits are marketed to people who aren't necessarily ill or at high risk for a disease, but who may be just curious or concerned about their risk for different disorders. Some of these tests require a physician's prescription, but many are sold directly to consumers on the Internet. The commercial tests examine a small number of the more than 20,000 genes in the human body and, in theory, predict your risk for conditions such as heart disease, colon cancer, and Alzheimer's disease; determine disease carrier status for pregnancy planning; and identify genetic variants that increase or decrease your ability to metabolize alcohol and certain drugs. Many also offer ancestry tracking identifying clusters of gene variations that are often inherited by a group of people with a common origin.

If you want to take a test, you will need an e-mail account and Internet access. After registering (and paying with a credit card) through the company's Web site, you'll be mailed a kit with instructions for collecting cells through saliva or a cheek swab. You mail the sample to a lab where it is analyzed and you receive a report within a specified time. Material accompanying your report may recommend strategies for reducing your risk of developing the condition your genes predict. You may also get telephone or e-mail access to a genetic counselor.

Commercial genetic tests are under scrutiny by the federal government. When Pathway Genomics announced in May 2010 that it would market its test kits through Walgreens drugstores, a Congressional committee launched an investigation. Meanwhile, the FDA has notified several consumer genetic-testing companies that they must apply for approval of the tests as medical devices (or explain why they think approval is unnecessary). The concern is that the companies are making scientifically unsupportable claims for the value of the tests in making health decisions. Walgreens has postponed plans to sell Pathway's kits in stores, and the investigations may force some changes in the way these tests are marketed.

If you're considering ordering a test kit, keep the following in mind:

They're expensive. The cost can run to several hundred dollars or more (see the chart, below), and it's not covered by insurance.

Your report will be based on incomplete knowledge. Your risk for conditions like heart disease, diabetes, and cancer depends on complex interactions between genes and lifestyle factors. Even diseases caused by a single gene, such as cystic fibrosis, are influenced by other genes that can affect, for example, the condition's severity. Researchers haven't identified all the genes responsible for these conditions or determined how factors such as diet or exercise influence the expression of those genes. Moreover, in many cases, the gene variations identified by the tests are only slightly associated with risk, or there is little good evidence to support any association.

The effects of a gene variation usually depend on other hereditary factors. It's important to get as much information as you can about members of your family and interpret the test results in that context. For example, if your father had a heart attack, did it occur at age 40 or age 80? The online test kits can't take that information into account.

Most of the tests have not been clinically validated. It will take large studies to determine whether the gene variations used in these tests accurately predict disease.

The test may not tell you anything you don't already know. By middle age, medical exams and screenings have probably given you a good idea of your risk for heart disease, diabetes, or osteoporosis. If you're uncertain, you can consult one of the well-established cost-free risk calculators, which include the Framingham Risk Assessment Tool for heart disease (www.health.harvard.edu/heartrisk), the Diabetes Risk Test (www.diabetes.org), and the FRAX tool, which estimates the 10-year likelihood of a hip or other major fracture (www.shef.ac.uk/FRAX).

Knowing the results won't always be useful. Identifying a genetic risk may inspire you to adopt a more healthful lifestyle, but it could also prompt you to seek diagnostic tests you don't need. It could even make you fatalistic and discouraged. Correspondingly, the absence of a genetic risk could create a false sense of security.

The follow-up report offers mostly generic advice. You may find that the payoff your personal guide to better health is a letdown. The recommendations are likely to be very similar to guidelines set by the Centers for Disease Control and Prevention or the National Institutes of Health, which are based on large-group or population-wide studies.

Company (Web site)

Sample

Conditions

Price

deCODE genetics(www.decodeme.com)

Cheek swab

Carrier status for disorders, disease risk, drug metabolism, ancestry

$2000 for complete panel; $500 each, cancer or heart panel. Genetic counseling included in price.

23andMe, Inc.(www.23andme.com)

Saliva

Carrier status for disorders, disease risk, drug metabolism, ancestry

$429 for health panel (carrier status, disease risk, drug metabolism); $399 for ancestry; $499 for both. Genetic counseling available for additional fee.

Pathway Genomics*(www.pathway.com)

Saliva

Carrier status for pregnancy planning, disease risk, drug metabolism, ancestry

$399 for disease risk panel; $249 each for ancestry, pregnancy planning, drug metabolism. Genetic counseling included in price.

Interleukin Genetics(www.ilgenetics.com)

Cheek swab

Obesity, heart attack, B vitamin metabolism, bone loss

$149 each; discounted prices for two or more. Genetic counseling and consultation included in price.

*Disclosure: Harvard Health Publishing, publishers of Harvard Women's Health Watch, has a licensing agreement with Pathway Genomics unrelated to this article.

If you're still interested in ordering a genetic test kit, start by exploring the company Web site for answers to these questions:

How accurate are the results? This depends on the quality of the sample and the reliability of the laboratory performing the analysis. You'll want to know what the company will do if your sample is unusable. Some will refund your payment; others will let you submit another sample. You will also want to make sure that the lab is accredited. In the United States, most clinical labs are certified by the Center for Medicare and Medicaid Services.

How will I know what my results mean? Most Web sites provide sample reports that allow you to judge the quality of the explanation and advice you'll get. The Web site should also tell you whether you can get help interpreting the results from a medical geneticist or a genetics counselor.

Will my results and any risk-reduction strategies be useful? Most reports will indicate which genetic variations you have and offer a general idea of what they mean. The risks of developing specific disorders will usually be given as a percentage above or below average or characterized as "high," "low" or "average." You should ask yourself whether you really want to know if you're even at slightly elevated risk for a serious disease you can do nothing to prevent, such as amyotrophic lateral sclerosis, or ALS, better known as Lou Gehrig's disease.

Is my information confidential? Under the Genetic Information Nondiscrimination Act, you cannot be denied a job or health insurance on the basis of your genetic information except in companies with fewer than 15 employees. The law does not apply to life, disability, or long-term care insurance. Be sure to find out about how your sample will be stored. If you're using an online test, your results should be presented on a secure server, anonymously stored, and password protected.

Someday everyone's genome may be sequenced as a matter of course, and the information used to guide our health decisions and medical care through life. But at present there is no direct evidence that these tests offer any practical benefits; that's why they aren't covered by health insurance. Genetically individualized medicine will have its day only when the predictive power of the tests improves and the cost of sequencing an individual's complete genome falls from its current level of $10,000 to $15,000 to a level where it's practical for large-scale use.

Right now, almost everything these tests offer is also available through medical professionals. If you think your genes put you at higher-than-average risk for certain diseases, talk to your clinician or a genetic counselor. A face-to-face counseling session will be far more informative and personal than an online testing kit, and it may even be covered by your health insurance.

If you're interested in acquiring your personal genome, consider applying to the Personal Genome Project at http://www.personalgenomes.org. It's an open-ended study aimed at matching gene variations with diseases in 100,000 people. And don't overlook the low-tech approach to genetics. Compile a medical history of your family in as much detail and for as many generations as possible. Then, if your genome becomes available, you'll have a context to place it in.

Visit link:
Direct-to-consumer genetic testing kits - Harvard Health

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