Some of you may know that Oprah Winfrey has had genetic testing done for the purpose of exploring her ancestry. As reported by Conrad Phillip Kottak:
"Oprah Winfrey made headlines in 2005 when she reported that a DNA test had revealed her (highly unlikely) Zulu ancestry. A more plausible result in 2006 linked Oprah to the Kpelle people of Liberia and Guinea, the Bamileke people of Cameroon, and the Nikoya people of Zambia. Ever the DNA explorer, Oprah in 2011 reported her discovery, confirmed by genetic testing, that she had a younger half sister whom her mother had placed for adoption.” Window on Humanity, 5th edition, to be published October 2011 by McGraw-Hill
In medicine there are over one thousand genetic tests available for clinical use. What are genetic disorders and what do these tests screen for? In some cases genetic tests screen for diseases that are caused by a single gene, such as Cystic Fibrosis or Sickle Cell Disease. However, with increasing frequency, genetic tests screen for predisposition to diseases that are known to be multifactorial, such as type 2 diabetes, cardiovascular disease or depression. In 2010 a list of DTC genetic testing companies and the conditions that they screen for was compiled by the Genetics and Public Policy Center. Most DTC companies that market genetic tests are Internet based companies. The process involves sending a DNA sample off to the company in the form of saliva or a blood swab. The company then engages a laboratory to do genetic testing, and the testing results are returned directly to the consumer. The cost of DTC genetic testing ranges from one hundred to one thousand dollars.
Those who oppose DTC genetic testing argue that making this type of complex information available to the consumer without adequate counseling by a health professional could be dangerous, that the notion of relative risk is difficult to interpret, and that there is currently inadequate oversight of laboratories engaged in DTC genetic testing to ensure the analytic and clinical validity of tests. The FTC has issued a consumer alert warning the public that “some of these [DTC] tests lack scientific validity, and others provide medical results that are meaningful only in the context of a full medical evaluation.” Currently the FDA regulates commercial “test kits” to ensure analytic and clinical validity. However, the FDA does not regulate laboratory-developed testing. In addition to the regulatory concerns there are also concerns about DTC genetic testing and compliance with health information privacy, HIPAA.The American Society of Human Genetics has recently written recommendations with respect to DTC genetic tests. Regarding DTC Personal Genomics the National Human Genome Project states:
"The relationships between particular genetic variations and the presence or absence of specific diseases or traits are often tenuous and the interpretation of the findings can change over time. This makes the communication of clear and accurate genetic information challenging, even in ongoing face-to-face clinical settings. It is not known how individuals and society more broadly, might understand and interpret this information when it is provided directly to individual consumers."Despite these cautionary stances recent studies of consumers using DTC genetic testing have indicated otherwise:
"David Kaufman of the Genetics and Public Policy Center at Johns Hopkins University conducted an NHGRI-funded survey of 1,048 people who had purchased a DTC test from 23andMe, DecodeMe, or Navigenics. Kaufman reported that nearly everyone indicated that the risk reports they received from the companies were easy to understand, though some overestimated their understanding of the results. The group also asked respondents to interpret data for two fictitious people to gauge their understanding of the risk reports. Between 4 percent and 7 percent of the respondents misinterpreted what they saw. Kaufman said that just more than three-quarters of his team's survey respondents said that they ordered the test to improve their health, and some of the respondents said that they'd been motivated to modify their behaviors in light of their test results: 15 percent changed medications or supplements, and 14 percent began exercising more."
In another study, reported in the New England Journal of Medicine in February of 2011, consumers using DTC genetic profiling had no evidence of increased psychological distress, change in diet or exercise behavior, or use of preventive screening tests as a result of their genetic testing.
Given these results, is the medical community being overly cautious? Should the average consumer be trusted to order and interpret his or her genetic profile without a medical intermediary? Many DTC companies have been shown to produce results that have a high degree of analytic validity.
In the case of my recent patient, she seems to have a very reasonable attitude. Despite the test’s prediction of low cardiovascular risk, she did not write off her high cholesterol, but was still willing to treat it with medication. We should be able to interpret relative risks in the context of complex multifactorial disease and the most recent clinical data. Though in the present its clinical applicability seems limited, in the future we will be increasingly tasked with managing this information alongside of our patients, who like Oprah, will be ever curious to learn more about their genetic origins.
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