Risks of Personalized Medicineby Jennifer Gibson, PharmD | January 15, 2012
Anyone who has taken high school biology has probably heard one of the corniest biology jokes around: How do you tell a girl chromosome from a boy chromosome? Pull down its genes. While this has been a useful (if not really funny) mnemonic for teaching students about life science, now individuals are beginning to play genetic versions of I’ll-show-you-mine-if-you-show-me-yours by actually examining their genes. Not much more than a decade has passed since the completion of the Human Genome Project, but, already, direct-to-consumer (DTC) genome mapping and genetic testing are available with little more than a cotton swab and an envelope between you and your DNA.
Personalized genomic information is used to individualize prevention, diagnosis, and treatment of diseases. Genetic variants can now be relatively easily identified and used as markers for diagnosis and prognosis and targets for treatment. But, the clinical functionality of this information is limited, and many questions are unanswered regarding the role of behavior and ethics as related to genetic testing. Proponents of ubiquitous genome mapping claim that identifying genetic information (and, therefore, risks) will lead to improved public health by motivating lifestyle changes. But, DTC testing occurs at the discretion of an individual alone, often without the input of a healthcare provider, prompting opponents of the tests to claim increased health risks — physical, mental, and emotional — as a consequence of the test results.
In a recent review of several studies that evaluated behavioral responses to DTC genetic testing, very few studies identified significant changes in individual behavior as a result of disease-specific genetic testing. The sample of consumers was, as a whole, healthier than average Americans, reporting daily consumption of fruits and vegetables and physical activity. The authors report that this group was already motivated to adopt a healthy lifestyle, and there was little room for improvement, regardless of the genetic predispositions revealed by the tests.
Also noteworthy was the finding that most of the DTC tests reported results in terms of relative risk instead of actual risk. Without an understanding of statistics or risk analysis, a report of relative risk might make individuals unnecessarily anxious or worried about their risk of disease. Further, many tests evaluate many gene variants at once, so individuals are able to retrieve risk information regarding tens – up to, potentially, hundreds — of diseases and conditions at once. Again, this information overload, without the training or knowledge to sort through what is important and what is not, can cause unwarranted concern, and possibly inappropriate interventions. Additionally, a large number of diseases and conditions for which DTC genetic tests check are largely associated with environmental and lifestyle factors and family history – risks that a consumer likely already understands.
Many organizations and groups that evaluate genetic testing and genomic applications do not support routine genetic testing, DTC or under the supervision of a healthcare provider. The biological mechanisms underlying diseases’ connections to genetic markers are largely undefined and the level of intervention that alters risk is unknown in most cases. And, for many disease states, there is no long-term data that shows improved health or disease outcomes related to genetic testing results. Traditional risk factors are more precise, measureable indicators of disease progression and/or treatment effectiveness.
Thanks, at least in part, to crime scene and medical dramas (real-life and fictional), the study of genomics and genetic risk analysis has been met with understandable enthusiasm, even from outside of the scientific world. But, the enthusiasm should not be without hesitation. The burden of having information, but not understanding how to interpret it or apply it clinically, can cause tremendous challenges to individuals and their families. And, it calls into question the ethics of DTC testing and the truthfulness of advertising and information provided by DTC tests. Further, the risk to future health care provision that may come as a consequence of personalized genotyping and phenotyping is left out of many discussions. Insurance coverage could be altered or denied due to supposed genetic risks. Discrimination could result owing to assumed predispositions. Judgments could be concluded based on incomplete information.
In a medical test-for-everything age (even if we don’t know what to do with the results), individuals are sometimes asked to make choices about their future health, the life of a developing fetus, or treatment options for a family member based on genetic testing. If there is not a trained counselor or healthcare provider available to deliver the correct and relevant information, people may not be able to make the most informed decision. Personalized medicine will likely revolutionize the way medicine is practiced, and likely lead to improved overall public health, but personalization includes much more than just genes; individuals, time, circumstances, and social norms dictate how and when information should be obtained and interpreted.
Bloss CS, Madlensky L, Schork NJ, & Topol EJ (2011). Genomic information as a behavioral health intervention: can it work? Personalized medicine, 8 (6), 659-667 PMID: 22199991
Henrikson NB, Bowen D, & Burke W (2009). Does genomic risk information motivate people to change their behavior? Genome medicine, 1 (4) PMID: 19341508
Offit K (2011). Personalized medicine: new genomics, old lessons. Human genetics, 130 (1), 3-14 PMID: 21706342
Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group (2010). Recommendations from the EGAPP Working Group: genomic profiling to assess cardiovascular risk to improve cardiovascular health. Genetics in medicine : official journal of the American College of Medical Genetics, 12 (12), 839-43 PMID: 21042222
Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Working Group (2011). Recommendations from the EGAPP Working Group: routine testing for Factor V Leiden (R506Q) and prothrombin (20210GA) mutations in adults with a history of idiopathic venous thromboembolism and their adult family members. Genetics in medicine : official journal of the American College of Medical Genetics, 13 (1), 67-76 PMID: 21150787
Image via Chepko Danil Vitalevich / Shutterstock.
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