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Those of you who followed Randy Dotinga’s two-part series on his genetic test (as well as you, Randy) will find this New York Times story interesting.

The story reports on a series of commentaries published in The New England Journal of Medicine about the validity of genetic testing.

It seems researchers don’t put much stock in tests like the one Randy took (and paid $300 for), which told him that he has a higher-than-average risk of getting colon and prostate cancers.

Since decoding the human genome in 2003, researchers have been working on “genomewide association” studies that compare the genomes of sick and healthy people with the idea that the comparisons will pinpoint which genes are responsible for common diseases, according to the Times story. However, the studies haven’t provided the genetic links researchers hoped they would. Here is an excerpt from the Times story:

A set of commentaries in this week’s issue of The New England Journal of Medicine appears to be the first public attempt by scientists to make sense of this puzzling result. One issue of debate among researchers is whether, despite the prospect of diminishing returns, to continue with the genomewide studies, which cost many millions of dollars apiece, or switch to a new approach like decoding the entire genomes of individual patients.

The unexpected impasse also affects companies that offer personal genomic information and that had assumed they could inform customers of their genetic risk for common diseases, based on researchers’ discoveries.

These companies are probably not performing any useful service at present, said David B. Goldstein, a Duke University geneticist who wrote one of the commentaries appearing in the journal.

“With only a few exceptions, what the genomics companies are doing right now is recreational genomics,” Dr. Goldstein said in an interview. “The information has little or in many cases no clinical relevance.”

The good news for Randy is that his chances of getting either prostate or colon cancer might not be as great as his test indicated.

Dr. Kraft and Dr. Hunter say that a person’s genetic risk of common diseases can be estimated only roughly at present but that estimates will improve as more variants are found. But that means any risk estimate offered by personal genomics companies today is unstable, Dr. Kraft said, and subject to upward or downward revision in the future.

Further, people who obtain a genomic risk profile are likely to focus with horror on the disease for which they are told they are at highest risk. Yet this is almost certain to be an overestimate, Dr. Kraft said.

The reason is that the many risk estimates derived from a person’s genomic data will include some that are too high and some that are too low. So any estimate of high risk is likely to be too high. The phenomenon is called the “winner’s curse,” by analogy to auctions in which the true value of an item is probably the average of all bids; the winner by definition has bid higher than that, and so has overpaid.

DAVID WASHBURN

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