miércoles, 30 de noviembre de 2011

Interpreting Risk: Direct-to-Consumer Genetic Testing || NCI Cancer Bulletin for November 29, 2011 - National Cancer Institute

Interpreting Risk: Direct-to-Consumer Genetic Testing

Woman using a cheek swab to collect DNA for a genetic testGenetic testing requires a DNA sample, which is often collected with a cheek swab.

In the winter of 2009, Shannon Behrman ordered a genetic test online because she was curious to know whether she had inherited her family's increased risk for melanoma. The direct-to-consumer (DTC) genetic test revealed an increased risk for melanoma, as well as for autoimmune disorders, but average risk for breast cancer, Parkinson disease, and most other diseases.

She received the test results without ever speaking with a doctor or a genetic counselor. Unlike most customers, however, Dr. Behrman has a Ph.D. in molecular biology and is a health communications fellow in NCI's Office of Cancer Genomics

DTC genetic tests are DNA tests that are marketed and sold directly to the customer without a doctor's order or a consultation with a genetic counselor. In recent years, the tests have become more accessible as many new genetic testing companies have emerged. Moreover, prices for DTC genetic tests have continued to drop, increasing their availability to the general public.

With greater public access to DTC genetic tests, researchers are examining whether members of the public will be able to accurately interpret their test results without the aid of genetic counselors.

Public Perspective

A recent study in Public Health Genomics reported that although members of the general public are likely to think that DTC genetic test results are easy to understand, they may not interpret them correctly. The authors also found that the general public thinks DTC genetic test results are more helpful in making decisions about medical care than genetic counselors think they are.

For the study, the researchers asked members of the general public—in this case, the Facebook friends of the lead researcher—and members of the National Society of Genetic Counselors to interpret mock DTC genetic test results. The Facebook friends of the principal investigator were not a representative sample of the public, however. On the whole, the subjects were young, white, female, highly educated, and mostly employed in the health care field. Because this is a skewed population, the results of the study may underemphasize the challenges the general public may face when interpreting DTC genetic test results.

Although most subjects correctly interpreted whether the test results meant more or less risk, overall, they did less well than the genetic counselors. Members of the general public also trusted the test results more than the genetic counselors did.

The researchers note that if members of the general public misunderstand the meaning of their DTC genetic test results they may experience unnecessary anxiety or feel falsely reassured about their health. Both outcomes could ultimately cause harm if, for example, they led to unwarranted changes in screening behavior.

A Third Possibility

The study findings did not surprise Dr. Jean Claude Zenklusen of NCI's Office of Cancer Genomics. In his experience, most people hear what they want to hear. "If you tell them their risk is lower, but not zero, they think 'OK, I'm great!'" he explained. He added that many people don't pay attention to a test result that shows they have increased risk, but those who do can become overly concerned.

Dr. Gillian Hooker of the Johns Hopkins Bloomberg School of Public Health/National Human Genome Research Institute (NHGRI) Genetic Counseling Training Program noted a third possible outcome: A finding of an increased risk on a DTC test could cause the person to change his or her behavior. For instance, she said, if someone received a test result that showed higher risk for a disease, and if evidence-based interventions were available to reduce that risk, that person could choose to change his or her behavior to reduce the risk of that particular disease.

For Dr. Behrman, the DTC genetic test results didn't reveal new information. "[My increased melanoma risk] is in line with my family history," she said. She has yet to make health changes or seek a genetic counselor for interpretation. "I just try to be healthy and slather on the sunscreen," she said.
You should have full access to your genome, but companies bear a responsibility to report in a responsible way.
—Dr. Jean Claude Zenklusen

A major obstacle in interpreting DTC genetic test results is numeracy. Numeracy, analogous to literacy, is a person's ability to correctly read and interpret numbers. Dr. Hooker noted the challenges of numeracy. "It's really hard to imagine what a difference of 1 or 2 percent means for your health," she said. "There's a fair amount of data in the risk communication literature that says that people translate risk much as the paper described."

Dr. Behrman noted a similar issue in her DTC genetic test results. "If I look at the results for my melanoma risk, it shows I have a twofold elevated risk of 2.4 percent. For the average person, when they see these numbers, they may just think, 'that's a twofold risk!'" But people receiving such a result should note that even though the risk may be double the average person's risk, it is still, at 2.4 percent, a fairly small risk.

Communication scientists recognize that the way risk information is reported influences how it is perceived. Indicating that "2 in every 1,000" people with a genetic predisposition for a disease will develop it, compared to "1 in every 1,000" people in the general population, provides more complete information than saying that an individual is "twice as likely" than the average person to contract a disease. The former presentation is referred to as absolute risk, the latter as relative risk. Most risk communication experts argue for using absolute risk estimates when communicating risk information to patients to provide greater context and more meaningful information.

Medical Paternalism

Given the challenges in interpreting genetic results and the serious possible consequences of misunderstanding, some companies are offering testing only through a doctor or genetic counselor.  "I understand how [a result indicating higher risk] could be alarming to people who aren't familiar with biology or statistics," explained Dr. Behrman. "If all you see is elevated risk, you panic." She added that ordering her DTC genetic test through a doctor would not have been a significant barrier.

Some argue that going through a doctor could be a barrier to accessing one's own genetic information.
"There is some concern about medical paternalism," said Dr. Hooker, referring to the philosophy that certain health decisions are best left to health care providers. "It's something I struggle with myself. To what extent do people have the right to access DTC genetic testing directly, or is allowing the consumer that access irresponsible?"

Dr. Zenklusen also takes a moderate path. "Your genome is yours," he said. "You should have full access to your genome, but companies bear a responsibility to report [genetic test results] in a responsible way." He added that the method of returning results should not be "over-reassuring or over-scaring."

The Public Health Genomics study suggests that research must be continued in several areas: risk communication, the best formats for communicating genetic information to patients, the connections between SNPs and disease, algorithms to find causative mutations, calculations to interpret genetic data, and other modifiers of our genomes.
Emma J. Spaulding
More information: Cancer Genetics Risk Assessment and Counseling (PDQ)
NCI Cancer Bulletin for November 29, 2011 - National Cancer Institute

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