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Insight & Intelligence : Oct 16, 2009
Jumping On Genetic Testing—The War of the SNPs
Molecular diagnostics still have a long way to go before they can properly deliver on all their promises.!--h2>
How many SNPs does it take to provide a definitive disease risk profile? Quite a few, apparently, as companies continue to pile them higher and deeper into genetic tests. Firms have bet that these tests will be widely adopted by physicians and the public to predict everything from risk of lung cancer among smokers, to prostate cancer, to Alzheimer’s disease, to baldness.
Major players include deCODE genetics, Navigenics, 23andMe, and Proactive Genomics. In January Proactive Genomics made available a $300 prostate cancer genetic test based on five SNPs, called Focus5. deCODE’s $500 PrCa test was announced less than a month later, for analyzying eight SNPs. Navigenics offers a personalized DNA profile, explained by a genetic counselor, for $2,500 but reduced its price several months ago to $999. 23andMe and deCODE also advertise their own versions of such profiles.
If genetic testing companies can survive long enough, SNP testing may achieve some potential by helping to identify individuals who could benefit from further testing. Accurately screening for risk of developing prostate cancer, for example, could help avoid subjecting relatively low-risk individuals to more extensive, invasive, and expensive procedures.
SNP-based test results provided in the context of other risk factors may also encourage individuals to change health-averse behavior. PHD Diagnostics recently introduced a test that identifies smokers and ex-smokers at the greatest risk of developing lung cancer. On its website the company recognizes that “the ability to clearly segment a group of otherwise similar people into different risk groups is one of the keys to creating a clinically useful test. While several individual SNPs have been linked scientifically to one of the many complex factors that may underpin the development of lung cancer, by themselves these SNPs do not provide a strong signal or differentiator among various people.”
PHD president Bob Walker remarked that smokers often suffer from optimistic bias, the belief that bad outcomes happen to other people, not them. Respiragene provides an easy-to-understand score and personalized information that doctors and patients can use to help individuals take the steps required to quit smoking and improve their overall health, he noted.
Would clinicians use SNP-based tests to screen patients and determine their need for further testing? Prostate cancer is illustrative of a fundamental conundrum; Eric A. Klein, M.D., chairman of the Glickman Urological and Kidney Institute, writing in the October issue of the Cleveland Clinic Journal of Medicine, referred to the “seemingly opposite conclusions” reached by two large studies evaluating PSA testing. Dr. Klein commented that “in spite of some recent studies, or perhaps because of them, we still are unsure about how best to screen for and prevent prostate cancer.”
A program initiated this month at Beth Israel Deaconess Hospital Medical Center seeks to familiarize pathologists in training with genetic tests marketed to consumers. It is intended to help doctors help patients derive true meaning from these tests. Mark Boguski, M.D., associate professor of pathology at Harvard Medical School and one of the program instructors, commented that the program seeks to prepare trainees “not because the technology is ready for prime time today, but because people are using it, and it’s clear it’s going to play a role in the future.”
Patricia F. Dimond, Ph.D., is a principal at BioInsight Consulting. Email: [email protected].
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