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Experts: Genetic Test Offers 'Information Without Knowledge'
Geneticists tell WebMD that the Pathway test is probably very accurate, as far as it goes.
"They are not sequencing the genes, just the SNPs," Jeffery Vance, MD, PhD, chairman of genetics at the University of Miami Miller School of Medicine, tells WebMD.
This means that while the test accurately identifies the most common variations on a gene linked to disease, it may miss rarer or yet-unknown variations that have the same effect.
"They could test for the six common SNPs that are most common ones that cause a disease, but a lot of other ones on the same gene could also go bad," Vance says. "So absence of information like that does not give you clean bill of health."
Even so, the test will accurately identify a large number of health-related risk factors. That's both good and bad, says Robert Marion, MD, director of genetics and developmental medicine at Montefiore Children's Hospital and Albert Einstein College of Medicine, Bronx, N.Y.
The good news, Marion says, is the availability of genetic tests means we are entering a new age of personalized medicine.
"We will be able to take a sample of DNA from a newborn or fetus or adult and analyze all 20,000 genes and come up with the profile of this person's lifetime disease susceptibility," Marion tells WebMD. "So people with susceptibility to diabetes, for example, will know they should be at a good weight, have a good diet, and pay attention to blood glucose levels earlier in life than they might otherwise have done."
The bad news, Marion says, is that it's extremely difficult to interpret the information that comes back from genetic testing.
"It opens up a Pandora's box," Marion says. "For a lot of other things they are testing for, we are not at a point yet where we can understand the results in a way that will be helpful to most families."
Vance uses even stronger language.
"They are giving people information without knowledge," he says. "The question is not whether a person has a risk gene but how much risk is involved. The average risk gene for a common disease is probably one and a half times the normal risk. So if it takes 100 pounds of risk to get the disease, these may be 1-pound risks."
And as every expert who spoke to WebMD is quick to note, genetic risk is not destiny. There is robust interplay between a person's genes, a person's lifestyle, a person's environment, and a person's experience. Genes, particularly SNPs, are only part of this complex equation.
"A lot of people who have a genetic risk for a disease never get the disease," Vance says. "And a lot of people who get a disease never had that genetic risk."