Field of Science

Personal genetic testing, available soon at your local pharmacy

This past week, Pathway Genomics and Walgreens announced that they would start selling Pathway’s genetic testing kits at 6000 Walgreens stores. I thought this was good news – I, for one, would like to be able to run my own genetic tests. I’d like to know what risks my genes might carry, particularly if there was something I could do to reduce those risks. But what does Pathway’s test tell you, and is it worth it?

Pathway has been selling its testing kits since September, but selling them at a large chain store like Walgreens would undoubtedly reach many more customers. After their joint press release last Tuesday, though, someone at the FDA noticed, and stepped in to ask a few tough questions. In a letter on May 10 (read it here), the FDA told Pathway that they had to get FDA approval for their diagnostic kits, or else explain why they don’t need it. Pathway claims its kit is exempt from FDA approval, but that might be a tricky argument to prove. After the FDA sent its letter, Walgreens announced that it would hold off for now on selling the kits.

Meanwhile, the real question is, what will Pathway’s test tell you about your genes? Some biomedical scientists are saying that the science of genetic testing is too new to offer directly to consumers. They argue that the results of a genetic test are difficult to interpret, and that patients shouldn’t be given this complex information without expert guidance. Stanford University’s Hank Greely, quoted in the Washington Post, said "Information is powerful, but misunderstood information can be powerfully bad." Are doctors just trying to protect their business, or are they right? I decided to take a look.

Pathway promises to tell you about your risk for up to 70 diseases and conditions, if you pay $399 for the full suite of tests. (That's the price if you order directly from Pathway, which you can do right now. The Walgreens price was supposed to be lower.)

For example, if you are a carrier of the cystic fibrosis gene (which is included in the Pathway test), and if your spouse is also a carrier, then as a couple you have a 25% chance of having a child with cystic fibrosis. The genetics of this disease are well understood, and the test for the mutation should be highly reliable. This seems like a good value to me, and I see no reason why people shouldn’t be allowed to know if they’re a carrier for cystic fibrosis; it may be important to their future plans for having children.

For other diseases, though, the Pathway test provides much more ambiguous information. Let’s look at late-onset Alzheimer’s disease, something that almost everyone worries about as they get older. The Pathway site doesn’t specify which gene they test, but there is no known “Alzheimer’s gene.” Research on Alzheimer’s has demonstrated that some genetic mutations are associated with an increased risk, but the picture is far from clear. For example, mutations in the Apolipoprotein E (APOE) gene on chromosome 19 appear to increase the risk for Alzheimer’s after age 60. According to the National Institute on Aging, the e4 (epsilon-4) variant of this gene:
“occurs in about 40 percent of all people who develop late-onset AD and is present in about 25 to 30 percent of the population. People with AD are more likely to have an APOE e4 allele than people who do not develop AD. However, many people with AD do not have an APOE e4 allele.”
Complicated, no? And this is the clearest association between a genetic mutation and Alzheimer’s — a half-dozen other genes are associated with slightly increased risk, and research is ongoing. So should anyone be allowed to test his/her genome for this mutation?

Yes, emphatically yes!

It’s my genome, and I should be able to look at it if I want to. So what if the information is complex? If someone is curious enough to pay for this test, then when they get their results back, perhaps they’ll be motivated to learn more about genetics so that they can understand their own risk. Giving people information about their own genome seems like a great way to educate the public, and to make people more aware of the power of genetic information. Of course there are risks: charlatans might offer to sell bogus treatments for all kinds of genetic conditions, for example. People might misinterpret the results. But that doesn’t mean we shouldn’t allow people to discover more about themselves.

In a very real way, genetic information is no different from other medical facts. We have easy access to our blood pressure numbers, and no one is suggesting that we shouldn’t, despite the fact that interpretation of blood pressure numbers can be complicated. (For example, should you reduce salt intake, or take statins to lower your blood pressure, or change your lifestyle in other ways?)

I hope the FDA allows Pathway to sell its DNA test at Walgreens. Personally, I think the value of the tests they’re offering today is mostly to satisfy curiosity – we don’t have treatments for most of the genetic diseases they can detect, so there's not much you can do about them. Some of the results will be useful to some people, though, and over time we’ll develop new treatments that will make more genetic tests valuable. Now that Pandora’s box is open, we can’t close it again. And we shouldn’t.

2 comments:

  1. I would like to know the error rate of the allele calls though. And I want someone other than Pathway Genomics making the calculation.

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  2. Whether or not to do genetic testing can be a complicated question. Sometimes it is very useful, sometimes not. Genetic testing may be useful for family planning. When parents have knowledge of their carrier status, they can take precautions to prevent a severe a genetic disease in the unborn child. This may lead to difficult moral and ethical questions when applied to the unborn child. In some cases gene testing is useful to confirm a diagnosis, such as alpha 1 anti-trypsin deficiency in the asthmatic patient, or to confirm hemochromatosis in the patient with elevated ferritin. Gene testing may be useful to predict future disease risk, such as cancer risk with BRCA genes, so that preventive measures can be taken.
    In some cases, genetic testing is either redundant or simply not useful. For example, there is no reason to do genetic testing for type two diabetes when the fasting blood sugar is already abnormal and is a more useful marker. There is no reaosn to do genetic testing for famiial hypercholesterolemia when the routine lipid panel provides this information. Likewise, there is no reason to do genetic testing to determine eye color or hair color when a simple examination provides this obvious information. Very soon, the cost for routine whole human genome sequencing will become cheaper, and some day will be offered during routine clinical testing along with the CBC, blood count and chemistry panel.

    For More: http://jeffreydach.com/2008/05/05/understanding-online-genetic-testing-by-jeffrey-dach-md.aspx

    jeffrey dach md

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