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033108-3[1] - Science and technology Consumer genomics...

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Unformatted text preview: Science and technology Consumer genomics Taking your genes in hand Personal genetic testing is advancing rapidly. But beware of overselling ENETIC testing promises a lot. In par- titular, it promises to tell people things ranging from their risks of develop- ing ailments as diverse as heart disease, cancer and autism to how much coffee they can safely drink. It also promises a lu- crative market for those doing the testing. Single-gene tests. such as those for particu- lar forms of genes that predispose people to breast cancer. have been available for a while.This year. however,has seen the at- rival of commercial versions of techniques that can sample a person‘s entire genetic make-up, and do so in a way that will en- able him to benefit from future discoveries as well as existing knowledge. In many cases, knowing the risk will also allow (and might, indeed. encourage) someone to modify his behaviour to avoid a disease he is at risk 'of—or, failing that, to mitigate its consequences. Nevertheless. concerns are being raised about the accu- racy of some tests now on the market, and also their usefulness when the results are supplied direct to consumers. rather than with professional medical advice. Last year America’s Government Ac- countability Office said that genetic tests it had bought from four websites misled consumers into thinking they were at risk of ailments such as heart disease, osteo- porosis and type 2 (late onset) diabetes. In some cases, firms tricked consumers into buying “personalised supplements” that were actually no better than ordinary vita- mins. but cost $1,200 a year. More recently, on December 4th. the British govern- ment’s Human Genetics Commission published a review calling for greater regu- lation of genetic tests. One member of the commission recently went so far as to brand them a“waste of money“. Testing times Fraudsters can, of course, be found in any industry. But another part of the problem has been the science itself. Eric Brunner, an epidemiologist at University College, London. points out that he and his fellow researchers have struggled for years to try to understand the genetic basis of com- mon diseases. The field is plagued by small, weak studies that are hard to turn into statistically robust conclusions. As a consequence, most findings of associa- tions between diseases and particular genes {which often get reported widely in the media when they are announced) do not stand up to later scientific scrutiny. Yet the pace of commercialisation means that companies have often started selling tests based on the earlier studies by the time their results are discredited. Paul Pharoah, an oncologist at Cam- bridge University and a critic of some gene-testing firms, says that in the past tests for a gene called 5002 have been available, with companies claiming it was associated with an increased risk of breast cancer. However, Dr Pharoah and his col- The Economist December 8th coo? Also in this section 94 The $1,000 genome 94 A mummified dinosaur 95 Subliminalsmells same... strain .aiiijinn on personal _ ' technology,_appears on Ecorio_mist__com : oat-Fridays. The column can be vieweda't' -. .- -m_mnomist.somfte¢vleu. . ' leagues recently published the results of a large study which showed that 50132 is not associated with breast cancer after alL With luck, this sort of thing will be- come rarer as scientists gather more data. However, some people worry that even those tests that do what they say on the packet may not actually give the consumer useful information. A possible example of this is a gene called TCF7. which is the sub- ject of a test marketed by deCODE, an Ice landic firm. One form of the gene, TCF7L2, is strongly linked to type 2 diabetes. Hav- ing two copies of TCF7L2 (one from each parent} doubles your risk of getting dia- betes—that much is well established. But some researchers reckon that if you do not have any of the other risk factors for dia- betes, your chance of getting the disease will be so low in the first place that this doubling is not worth knowing about. The processes that lead to most dis- eases are not, however, the result of a sin- gle genetic failure. Instead, they involve hundreds if not thousands of genes inter- acting with one another. In the past geneti- cists have concentrated on genes that have large individual effects when they go wrong, because such effects are easy to spot. But particular combinations of genes that are not individually significant may also be important. This raises the question of how many genes at test needs to look at to yield a meaningful estimate of risk. Though the answer is not yet clear. Dr Pharoah reckons it is likely to be more than just two or three. Tests that look at only a handful of genes. he thinks, are simply not useful. The answer to that. of course, is more information. And it is here that the new generation of genome-wide tests comes in. These tests (which are being offered by de- CODE and also by 23andMe. a Californian company) analyse the pattern of hundreds 93 it) r of thousands of bits of DNA known as sin- gle-nucleotide polymorphisms (SNPs, of- ten pronounced “snips"). A SNP is a point on a chromosome where DNA routinely varies from one person to another. Many SNPS are associated with disease-causing forms of genes. and more associations are being discovered every month. Indeed. this year has seen a bumper harvest of strong, well-replicated associations be- tween SNPS and diseases such as cancer and diabetes. Analysing SNPS is not the same as an alysing a full genetic sequence. For that to happen routinely. the technology will have to improve a lot {see next article). However. deCODE and 23andMe are of- fering individuals a far broader look at their genes than has been possible before— and, in the case of deCODE. are backing their opinions with original research done . by the firm, rather than merely drawing on literature published by others. Yours, for a SN? Both firms take pains to point out that what they are offering is an “information service". not a “test”. and certainly nothing that is intended to diagnose a medical con- dition. And with his firrn’s existing test for res-1L2, Kari Stefansson. deCODE‘s boss, seems to agree that testing for this gene should be prescribed "in most instances” by a physician. However, he concedes that the wide-ranging SNP test will also tell cus- tomers how many copies of rcma they have. whether they have been through a doctor or not. . Whatever the disclaimers say (and one purpose they have is to help firms to avoid regulation) people are clearly going to be - getting medical information from such tests. For example. overweight customers who find they have two copies of TCF7L2 really do have something to think aboat. In time. of course, the regulators will catch up. Indeed. Dr Stefansson hopes that deCODE’s products will eventually be- come approved diagnostic techniques, rather than mere information services. But for the moment. this is still an area where buyer should definitely beware. And that is probably right. The technol- ogy of testing is improving fast and regula- tion risks slowing progress. Moreover. physicians' calls for scrutiny should them- selves be scrutinised, because genetic test- ing inevitably transfers power from doc tors to laymen. ' That transfer of power brings respon— sibility, of course—the responsibility of consumers, aided by the gene-testing com- panies themselves, to interpret their new knowledge sensibly. If they do not, doc- tors’ surgeries may be flooded with what have come to be known as the worried well. and regulation is sure to follow. If people do take responsibility. however, a healthier life awaits them. I ...
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