Genetic testing for disease risk won't work without your entire genome sequenced

April 16, 1:18 PMSacramento Nutrition ExaminerAnne Hart

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You may have seen the news in the April 13th issue of the New England Journal of Medicine that testing only a few gene markers for disease risk  doesn't tell the whole story. You have to test an individual's entire genome before you compare it with somebody else's who doesn't have any genetically-inherited disease. And until now, whole sequence genome testing had been priced above what most people could afford.

Some companies say they'll run your entire genome for a thousand dollars. But who's doing quality control? And who's watching the watchers?

These testing companies look at your personal genomic information. Then they tell you what risks you run of a certain disease that is supposed to show up in your markers. But it doesn't work that way, science found out. It's complex. Not one but many genes switch on and off as they interact with your environment, lifestyle, and what you eat.

The companies that have invested millions of dollars in gene testing may not be telling you much about your risk. They probably can tell you who's related to you, but not whether you're going to come down with a disease just because they think you're at risk to get it. Maybe you won't get it if you eat right, walk enough, find a place without heavy air pollution to live in, marry someone who smiles a lot, and watch your stress levels.

If you're testing for a very rare disease caused by a malfunction of only one gene, genetics testing can tell you what's wrong with that one gene. But if you're testing for common diseases such as diabetes or hardening of the arteries, they're caused by numerous variations in your genes, not just one gene.

And they build up during many decades to creep up on you later in life. Epigentic tags on genes are switched on or off also from lifestyle and nutrition changes, the environment, as well as stress levels.

Worse, you don't know you have these diseases, usually, until after you've given birth. So  you don't realize you're passing your possible gene variations for these diseases to the next generation. If you're in your twenties and feel invincible, you don't realize when you have children that  you're passing on the diseases of your grandparents to your children--maybe.

Genetic variations for the common diseases of aging are all over the population. Even if one grandparent lived to 105 and another grandparent succumbed to a blood clot at 65, some of your children may or may not inherit the clotting condition and others would live well over age 90.

And you don't know which child has what gene until the child reaches age 65 or older--or unless you sequence the entire genome for each individual. You can't test just a few snippets of genes, alleles, chromosomes, or bio-markers and report risk without knowing what the genes will do in combination with other genes in addition to input from the environment, food, and lifestyle of a person.

Sure, there are common variants for diseases found in large populations. But your risk even if you carry these gene variations is average or moderate. There's no stamp on your body with an expiration date or a startup date for a disease to strike.

So before you test for risk, think about what the test is going to actually show you. Do a reality check. Do you have very rare gene variants? Is there more than two people in your family with the same disease?

What diseases are inherited? Will you have your genes checked for serious mental disorders? Even if you have these issues in  your family, there are at least a thousand rare gene mutations or variations causing them. Sometimes lifestyle can override certain gene risks.

Ask the next gene testing company that tests for risk whether the test actually points at something specific. Did you ever wonder whether all the gene testing is done in the hopes that the billion-dollar drug companies will have one more drug to sell to correct "errant genetic pathways"?

Many genetic variants are responsible for a common disease. The job of the geneticist is to find more common gene variants. If they don't find the right genes, the big pharmaceutical companies will lose their hope of finding new drugs to correct genetic problems for common diseases that might better be helped with nutrition and lifestyle changes.

At the same time people whose children have rare genetic diseases can't find the right drug they need to thrive. The big pharmaceutical firms demur that it's because there isn't enough people with those rare genetic problems for the big drug companies to keep researching without the money from enough patients buying the drugs.

And what about the rare gene variants that don't have huge symptoms attached to their mutations? The solution to this problem could be to test everyone's entire genomes at an affordable cost. That way personalized medicine can be tailored to the individual. Time and money eventually will allow more gene variants to be studied.

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