Family history trumps genetic tests

Genetic tests have the aura of being scientific. But the old-fashioned family history appears to be more accurate and much less expensive.

A Cleveland Clinic researcher recruited 44 people to assess their risk of cancer by either preparing a  family history or relying  on a genetic test. Both indicated that about 40 percent had above-average risk – but picked the same people half the time. The genetic test did not identify the nine people who had a significant family history of colon cancer.

Likewise, researchers collected 101 genetic variants that had been tied statistically to heart disease in genome studies. They assessed and followed 19,000 women for 12 years to attempt to forecast disease. They concluded that the family history was a better predictor.

One reason family histories can be more accurate is that environment is a powerful influence on health. Family members generally share a common background, so the history reflects how shared genes expressed themselves in a given situation.

Family members often take important genetic information to their graves inadvertently without sharing it with relatives. According to one study, about 1 in 5 dying cancer patients could have shared important information with relatives through genetic counselors regarding the heritability of their conditions. In some instances, they could have left behind blood and tissue samples for future DNA testing. That would be a valuable legacy. (Genetic counselors help people understand their risk for genetic conditions. The National Society of Genetic Counselors website, www.nsge.org, lists them by zip code.)

Less than one-third of U.S. families have documented a health history, and many physicians are not particularly insistent that they have one. The U.S. surgeon general has established a website – https://familyhistory.hhs.gov – to help families create a history and share it with other relatives.

Many scientists have concluded that DTC genetic tests offer very little value. They say the increased risk posed by any given gene is so small that it is not information worth acting on. The best predictors of disease and death are already well known: age, gender, family history, health behavior and biomarkers such as blood pressure, blood glucose and cholesterol.

An international research consortium identified 18 new gene sites associated with obesity and 13 others tied to fat distribution in the body in 2010. The two studies, which one of the researchers called “exciting,” will not have much immediate clinical impact.

Michael Jensen, an obesity expert at the Mayo Clinic, told The Wall Street Journal, “If you just ask people whether their parents were obese or not, the ability to predict whether a person is going to be obese is better” than by examining the identified genes.

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