Are Genetic Tests Useful Part 2

DeCode C.E.O. Kari Stefansson is on the telephone from Iceland insisting that I immediately go on statins—cholesterol-lowering drugs that help prevent heart disease. A physician as well as an entrepreneur, he has just told me I am at a high risk for a myocardial infarction—a heart attack—based on a gene test run by his company.

"You have a very bad gene marker," he says, "you need to take this seriously!"

EXPERIMENTAL MAN David Ewing Duncan explores advances in personalized medicine and what they can tell us about ourselves.

I had just begun my own personal journey to delve into millions of DNA markers inside me to check for diseases, and already things were looking dire. Or were they? In the weeks after Stefansson's call, I would receive results from three new websites that tested my DNA and offered assessments of my personal genetic risk factors for not only heart attack, but also a raft of diseases ranging from diabetes to multiple sclerosis.

The findings suggest that this information is based on an exciting but still uncertain science that can produce contradictory results about something I take pretty seriously: my heart.

Stefansson had called me about a genetic marker identified by scientists as rs10757278. Last year, researchers at his company and elsewhere linked a certain version of genetic coding in this marker with an elevated risk of heart disease. This "variation" was discovered by comparing the genes of people in North America and Europe who have had a heart attack to those who haven't.

In the language of genetics, the high-risk result for this marker is a GG—the "G" coming from the familiar genetic symbols for nucleotides (G, T, C, and A) that are arranged in pairs along lengthy strings of DNA. These "base pairs" line up like computer code to direct the growth and functions of cells. Differences in these codes—in the letters—are what accounts for variation among people: everything from the color of one's eyes to the likelihood of developing a certain disease.

About 20 percent of Caucasians carry the GG, which confers about a 1.64 times the average risk factor for a heart attack—a 64 percent greater risk than average. This is a moderate risk compared with, say, someone with high cholesterol, who has at least two times the normal risk.

 

The other possible variations for this marker are AG, which gives a carrier about a 1.24 risk factor, and AA, which is a "1", an average risk. For Caucasian men, this average is about 40 percent that he will have a heart attack sometime in his life.

I apologize for getting into numbers and risk factors that may be mind-numbing to some. My defense is that we all need to begin to understand the language of markers and probabilities, which is likely to become part of basic health care in the next decade or so.

Gene	Gene Marker	At-Risk Mutation	Author's Results	Risk Factor	Source
CDKN2A/CDB	rs10757278	G	GG	1.64	DeCode

"I want you to call me when you start statins!" Stefansson said to me as our call wound up. I said I would think about it and told him good-bye, knowing that I was not about to go on statins based on a genetic risk factor that I didn't entirely understand.