Personalised genetic analysis

A report from The Economist, titled: Within spitting distance, from Nov 20th 2007 edition. Read the full story here (I think a subscription might be required), or see extracts below.

MEDICINE has long been a mysterious art. Some people are more susceptible to disease than others, and the pills and potions that may help one person leave others uncured. But the past few days have seen steps forward in personalised medicine, in which diagnosis and treatments are tailored to each individual’s genetic make-up. Two firms have unveiled products that allow the ordinary punter to get his genome decoded for about $1,000.

On November 16th deCODE genetics, an Icelandic company that has already developed genetic tests for several diseases, including type 2 diabetes, unveiled a service it calls “deCODEme”. Its scientists will analyse the DNA in cells taken from a customer during a cheek swab and compare the results with its database of hundreds of thousands of people’s genomes, as well as against known genetic defects linked to diseases. Customers can use the information to research their ancestry, body traits (such as eye colour) or medical conditions (such as diabetes).

Soon after, 23andMe, a Silicon Valley company funded by Google and Genentech, announced that its personal genetics product is also ready. In return for $1,000 and a generous gob of saliva, the firm will analyse a customer’s DNA and post the results on its website, whose social networking features (which allow users to meet strangers with similar genetic variations) are not unlike those of Facebook. Navigenics, another Californian start-up, is expected to unveil a more expensive (and more medically oriented) service soon.

Two keys have unlocked this market: a clever short cut and a clever chip. All people are 99.9% identical, genetically speaking. Therefore almost all of the 3 billion letters in the human genetic sequence are the same. Only at certain places is one letter replaced by another in a large fraction of the population. These points are called single nucleotide polymorphisms, or SNPs, and there are 10m or so of them. Looking only for SNPs is cheaper and quicker than analysing the entire genome.

The clever chip responsible for the actual analysis of DNA reduces an entire genetics laboratory to Lilliputian proportions. It consists of a glass slide with millions of small beads on its surface. Each of those beads is embedded with bits of DNA that are complementary to the places in the genome where interesting SNPs are located. When a person’s DNA sample is sliced up and spread over the slide, the fragments are attracted to the complementary bits of DNA and stick to them. Identifying the SNPs of note in an individual’s cells thus becomes straightforward.

Yet there are plenty of potential pitfalls that could yet slow the march to truly personalised genetics. If customers just want to explore their family roots or identify which relatives gave them green eyes, these new products may do the trick. However, as soon as they want to use them as reliable predictors of disease, trouble begins.

One reason is that scientists do not yet know exactly how the genetic variations they can identify cause disease, so the information provided may prove inconclusive or even misleading. Another problem is to do with regulation. Keen to avoid the scrutiny of the Food and Drug Administration, which does not yet have a role in overseeing this fledgling industry, all the firms are careful to emphasise that they are not providing medical diagnostics services—though they are plainly providing information that customers will use to assess medical risks. To inoculate themselves further, firms are encouraging clients receiving news of worrying genetic proclivities to seek medical or genetic counselling.

That points to another snag, however. In America, where these services are first being offered, telling one’s doctor about such test results will almost certainly result in a note being made in one’s medical file—and the content of that file is usually shared with an insurance company. That raises the possibility of genetic information being used to discriminate against individuals or to deny coverage, a scenario that many Americans fear.

To encourage confidentiality, both deCODE and 23andMe say they will accept customers anonymously, using aliases and PayPal accounts. But some commentators doubt that the information will remain private. For example, 23andMe says that anyone using its service must agree to have his data aggregated anonymously for research purposes, and deCODE says it would like to aggregate data too.

The latest step towards personalised genomics may cast light on the practice of medicine but it is also creating shadows of its own.

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