Originally published March 15 2009
Genetic Screening No Use in Predicting Heart Attack Risk
by David Gutierrez, staff writer
(NaturalNews) Genetic screening for the trait most strongly linked to early heart attacks does not, in fact, improve the ability to predict the risk of heart attack or other forms of cardiovascular disease, a new study has concluded.
"Once you already know the traditional risk factors, the additional information about the genetic variation doesn't help any," lead researcher Nina Paynter said. "It doesn't improve your ability to predict."
The trait in question is a type of genetic variation known as a single nucleotide polymorphism (SNP), occurring on chromosome 9. The variation, 9p21, is currently the strongest known genetic predictor of early heart attack. Although scientists are still unsure exactly what the function is of the gene that 9p21 is located in, carrying one copy of the genetic trait is believed to be associated with a 20 percent increased risk of early heart attack. The trait has also been associated with a significantly increased risk of other forms of cardiovascular disease, such as stroke, abdominal aortic aneurysm and intracranial aneurysm.
With genetic screening increasingly entering the public consciousness, some businesses have started offering commercial 9p21 screenings, purporting to help people estimate their heart attack risk. In the current study, published in the journal Annals of Internal Medicine, researchers from Brigham and Women's Hospital and Boston sought to determine if genetic screening of individuals could actually provide any predictive benefit.
"Gene patterns are associated with an increased risk of heart disease, and the higher risk patterns are common," Paynter said. "However, it was not known if knowledge of a person's pattern, when added to knowledge of traditional risk factors including family history of heart disease, would improve the ability to predict levels of future heart disease risk for that person and possibly help with treatment decisions."
In the end, knowing 9p21 status provided no benefit over knowledge of risk factors such as family history, blood pressure, cholesterol, diabetes status, smoking status and even levels of the arterial inflammation marker C-reactive protein.
The researchers assessed the 9p21 status of 22,129 white female health care professionals in the United States, along with several well-known cardiovascular risk factors. They then followed the participants for 10.2 years. All participants were free of major chronic disease at the beginning of the study.
The presence of 9p21 did, as in prior studies, correlate with a 25 to 30 percent higher risk of cardiovascular disease. This predictive effect was dwarfed, however, by those of other risk factors. When 9p21 status was incorporated into two common cardiovascular risk assessments, it only marginally improved accuracy in one test, while actually worsening it in the other.
"It seems unlikely that screening for SNPs in this region will be clinically useful in daily practice," the researchers concluded.
While the current study looked at the population-level value of 9p21 testing in predicting cardiovascular disease, Paynter noted that the tests are not useful for individuals, either.
"On a personal level, having the 9p21 variation tells you that your own personal risk is increased, but in middle age, women are at a fairly low risk anyway, and that 20 percent increased risk doesn't bump you up to medium or high risk for cardiovascular disease," she said. "For most people, it just puts you at a slightly higher, very low risk."
According to many scientists, the study calls into question the utility of genetic screening for chronic disease risk, in general.
"It's an important study that should give us pause that information about whether our DNA will trump what we know from established risk factors," said Harlan M. Krumholz of Yale University. "The genetic work is important in efforts to find targets for future therapies, but addressing modifiable risk factors is where we need to direct our attention."
Sources for this story include: www.reuters.com; www.washingtonpost.com; www.modernmedicine.com; www.theheart.org.
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