Byline: Sharon Begley
Why family medical history is key.
In this age of DNA, with for-profit companies scanning customers' genomes for DNA variants associated with disease and the "$1,000 genome" within reach, it seems positively antediluvian to bother with family medical histories. Why ask aging relatives what Uncle Harry died of when you can scrape some cells from your cheek and ship them off to a sequencing company to learn which diseases your DNA--which you might or might not share with Uncle Harry--has in store for you?
For two important reasons. The simplest is that many of the studies linking a gene variant to one or another disease are incorrect at worst and useless at best. The more interesting reason to rely on your family medical history is that genes do not act in a vacuum. Those realizations have now prompted the American Society of Human Genetics (ASHG) to declare family medical history "the gold standard" for assessing what diseases you are at risk for--a conclusion as surprising, given the source, as if Exxon declared solar-powered cars superior to the gasoline variety.
An estimated two thirds of the early studies linking an aberrant form of a gene to a particular disease turned out to be mistaken. The latest to implode is the purported link between a variant of a gene called KIF6 and cardiovascular disease. A study of 57,000 people found that genetic status had essentially no predictive value for coronary-artery disease, as had been claimed (the test is sold commercially for about $100). "This study puts the nail in the coffin," said Tom Quertermous of the Stanford University School of Medicine.
More interesting are correct but useless discoveries, in which a gene variant indeed raises your risk of some disease but knowing your genetic status doesn't make predicting your medical future any more accurate. A study this year looked at four gene variants associated with Alzheimer's. Adding them to traditional risk factors such as age and sex did nothing to improve prediction. A 2009 study focused on a genetic variant on chromosome nine linked to an elevated risk of cardiovascular disease (CVD). But when scientists added genetic status to traditional risk factors (such as high blood pressure, smoking, high cholesterol, and family history of heart attack at a youngish age), the crystal ball for who would develop CVD was no more accurate than with traditional factors alone. …