CHAPEL HILL - Thanks to accelerating genetic technology, the ability to live an examined life is at hand in a way that Socrates couldn't have dreamt of. Analyzing your genome at a million sites has become an afternoon's work, and complete analysis of your genetic code may soon be a reality.

Such capabilities promise great things for medicine. But while the medical community is trying to figure out how to use this information to improve health, the private sector is rushing to satisfy our drive to know ourselves in this new way with a variety of boutique genotyping services.

These offerings, widely publicized in the popular press, promise to analyze the consumer's genome for between $1,000 and $2,500, illuminating everything from their ancestry and ear-wax type to their risk for prostate cancer.

As such powerful information slips the bonds of the traditional health-care setting, it behooves to ask what we are likely to discover from such analyses. What are you likely to get after you decide to send a DNA sample (along with your credit card number)?

THINGS THAT ARE USEFUL TO KNOW. For the time being, useful results from such analyses with actionable implications will be rare. Arguably, knowing that I'm at a higher than average risk for heart disease or diabetes might add to my motivation to stop smoking, exercise, eat right and lose weight. But will those found to be at lower than average risk use genetics to abandon such efforts?

If the goal is to improve our health, common sense advocacy of healthy habits is likely to be far more effective than illusory "tailoring" of our advice through dubious genetic analyses.

THINGS WE ALREADY KNOW. One prominent commercial offering currently available lets you know that your DNA profile will inform you what color your eyes probably are. With apologies to Dave Barry, I'm not making this up. The narrator of the Web site's virtual tour informs us that his DNA analysis reveals his "chance of having brown eyes is 67%!" I don't know about you, but I'd prefer the increased certainty and reduced cost of looking in a mirror.

Likewise, learning that we are at risk for heart disease and that we should exercise and eat right is hardly new information.

THINGS WE DON'T REALLY WANT TO KNOW. This is a potentially disturbing but real category of results. Genetic testing to assess risk of Alzheimer's disease has been available for years. Yet the imperfect nature of such information and the utter lack of means by which to alter that risk make most individuals leery of pursuing such "information."

Genetic predictions are only probabilities, and like roulette, must be approached with caution; genetic information rarely confers certainty. Cashing in your retirement fund early because you are at an increased risk of Alzheimer's disease is a good way to end up destitute when you "luck out" and your predisposition to this disease fails to materialize as will often be the case.

Medicine's ability to prognosticate always exceeds its ability to intervene and genetics only widens this gap. Individuals -- whether patients or consumers -- deserve a clear discussion of whether they actually want all the information that can be obtained.

THINGS THAT AREN'T TRUE. Given the complexity of genomic analyses, many purported genetic risk factors will never be validated. Moreover, when a particular risk factor is found in a given population (e.g., Western Europeans), there is considerable doubt that the conclusions can be generalized to individuals from ancestrally distinct populations. Thus, minorities may receive particularly suspect results.

Next page >