Wednesday, August 27, 2014
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Do-It-Yourself Genetic Tests

LONDON – If you were hoping to pick up a DNA kit along with your shampoo from the drugstore, you would be out of luck. The United States Food and Drug Administration recently warned the giant pharmacy chain Walgreen’s to think twice before stocking personal genetic testing kits. As an FDA spokeswoman said, “These kits have not been proven safe, effective or accurate, and patients could be making medical decisions based on data from a test that hasn’t been validated by the FDA.”

Since the first personal genetic tests became available on the Internet three years ago, critics have raised concerns about their potential impact on patients and families, along with their accuracy. Some say that the tests are “genetic horoscopes,” and just about as scientific. Such misgivings have led to personal genetic tests being banned in several US states, as well as in European countries like France and Germany.

Personal genetic tests vary from one manufacturer to another. At one end of the market, there are companies offering to test for recessive red-hair genes or sexual chemistry. A firm called Scientific Match tests a small number of genes related to immune response, promising that it can put you in touch with partners whose genetic make-up will promise you a better sex life and your children a high natural immune response.

At the other end of the spectrum, firms like Navigenics and 23andMe offer tests for genetic predispositions to a range of medical conditions like Alzheimer’s disease, breast cancer, and diabetes.

Four main issues worry critics.

First, because these are only partial tests, they don’t cover all the bases. They target different combinations of SNPs (single nucleotide polymorphisms, or genetic variants). There are about three billion SNPs in the human genome, of which the personalized genetic testing companies each cover a fraction. That means that customers can and do receive widely different assessments from different firms of how likely they are to develop any particular condition.

In October 2009, the scientific journal Nature published an article describing how five researchers submitted their DNA samples to both Navigenics and 23andMe, to be tested for risk of 13 diseases. Three researchers were given opposite findings for major risks such as heart attack, lupus and type 2 diabetes. Although genetic knowledge could be empowering, a little knowledge can be a dangerous thing, especially if people take irreversible actions based on a “false positive” – or ignore measures like breast cancer screening because of a “false negative.”

Why don’t all the tests cover the same genes? To be blunt, genetic knowledge hasn’t advanced to the point where clinicians and scientists can generally link one gene, or even a set of genes, to one condition. This is the second source of criticism.

In the early days of genetic testing, researchers had considerable success in identifying the genetic basis of conditions such as Huntington’s disease. But Huntington’s, linked to a certain number of repeats in a single genetic marker, is unrepresentative of the role that genes play in causing disease. Most diseases are not caused solely by genetic factors, and linkage to many genes is much more typical for those that do have a strong genetic association.

Genetic medicine is advancing at a rapid pace, but its clinical applications seem to be receding. Earlier this month, researchers at the United Kingdom’s Institute of Cancer Research identified five new gene regions associated with breast cancer, taking the total up to 18. But the more genes that are involved, the less feasible it becomes for personal genomics to test for all of them, and the more difficult the consumer will find it to interpret the results without professional help.

That is the third source of concern about do-it-yourself genetic tests: they don’t necessarily include counseling about the results (although Pathway says it offers genetic counseling by phone). What, for example, should consumers – and family members who may have inherited similar predispositions – if they test positive for genes linked to incurable conditions?

Moreover, after the DNA sample has been put in the mail, it is no longer the customer’s property, and the company decides what to do with it. Scientific Match says that it destroys samples after the “matchmaking” in order to minimize the risk of a violation of privacy.

But other firms have been accused of having more interest in developing a “biobank” of samples and data than in genetic testing. As Jesse Reynolds of the Center for Genetics and Society writes, “Just as the traditional business model of newspapers is to get revenue not from readers but from advertisers, personal genomics companies see the potential profit not from the consumers themselves but from the compiled databases – likely in the form of selling access to them.”

Drug companies and other firms may well be eager to buy biobanks on which they can test their products for differential responses according to patients’ genetic make-up. This new development, called “pharmacogenetics,” aims to deliver better-calibrated dosages and more effective treatments.

There is certainly nothing wrong with that, but it does seem odd that customers are effectively paying a firm for the privilege of donating their DNA to its database. As 23andMe founder Anna Wojcicki puts it, “We will not sell individuals’ data, but the database as a whole will have enormous value.”

In fact, that is more doubtful than it seemed when the companies first drew up their business plans. The cost of full-genome sequencing has fallen rapidly, from $27 billion for the first genome ever completed to around $10,000 now, which makes partial genome databases much less attractive. One major company has already gone bankrupt; another is laying off staff.

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