By Robert Bazell,
Chief Science and Health Correspondent
NBC News

A readout of all of your DNA? You’ll get it soon. Many wealthy people have theirs already, but within years because of ever-accelerating technology it will be cheap enough for all, including every baby at birth.

So what will this “genetic blueprint” tell us of our future health?  Not much, according to an important study out Monday from a group of scientists at the Johns Hopkins University School of Medicine. They analyzed thousands of identical twins. Twins share the same genes from birth, so their experiences illustrate the insights to be gained from any individual knowing his or her genetic future.

The scientists looked at 24 common diseases and found that occasionally the complete genetic blueprint will alert people that they run a risk far higher than others for a certain disease. But most will get very little useful knowledge. The scientists presented their work at the annual meeting of the American Association for Cancer Research and published it simultaneously in the journal Science Translational Medicine

“Genomic tests will not be substitutes for current disease prevention strategies,” said Dr. Bert Vogelstein, one of the authors and a pioneer in the search for genes that increase cancer risk. 

So a blood test of the future will not free you from the need to eat healthy, exercise, keep extra weight off, not smoke and get useful cancer detection tests such as pap smears and colonoscopies. Nor will it relieve the ongoing possibility of nasty surprises about diseases you may have never feared.

But isn’t our genetic blueprint our destiny? Many scientists thoroughly believed that not long ago. As they have learned more about genes, however, that prediction appears ever more simplistic. 

Most diseases arise from a complex mixture of the genes we inherit from our parents at birth— not only what is measured in the whole gene test, but also our lifestyle and environment, and random events such as gene mutations occurring in individual cells in our body later in life.

One of the best examples of the dilemma of genetic testing comes from a test that has been on the market since 1996 for the cancer mutations called BRCA1 and BRCA2

If a woman is born with one of those mutations she has a 35 percent to 84 percent chance of developing breast cancer by age 70 and a 10 percent to 50 percent risk of getting ovarian cancer. Those odds are so high that women who test positive often elect to have their ovaries and/or breasts removed before cancer strikes. In those situations the test saves lives. But the problem is that fewer than one in 1,000 women carry those gene mutations.

And if women test negative for the gene mutations, the negative test does not at all mean she is in the clear. There are so many factors that increase risk for breast and ovarian cancer that a woman who tests negative for BRCA1 and BRCA2 only reverts to having the same lifetime risk as all other women – a 12 percent risk for breast cancer and 1.5 percent for ovarian cancer.

That set of complexities mirrors the situation for the thousands of other genes we carry that have some association with a disease.  If everyone has a complete gene profile, a small number can learn they have a great risk for something.  But for most, the information is minimally significant.

Not long ago many investors saw whole gene sequencing as a future gold mine. But these latest results show that the tests are unlikely to make many people wealthy -- or healthy.

Related stories:

Rethinking how we confront cancer: Bad science and risk reduction

Experts: Wide 'autism spectrum' diagnosis may explain diagnosis surge

Daily serving of red meat raises risk of cancer, heart disease

Robert Bazell is NBC's chief science and medical correspondent. Follow him on Facebook and Twitter.

By Robert Bazell
Chief science and medical correspondent
NBC News

During the briefing for reporters Thursday on the CDC’s latest findings that one in 88 children in the U.S. (one in 54 boys) has a diagnosis of some brain disorder that falls on the “autism spectrum,” there was a polite but revealing dust up.  Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, conceded –in response to a question– that the increase in cases could be the result in changes in the way such disorders are diagnosed.  Then Mark Roithmayr, president of Autism Speaks, the biggest activist organization concerned with the disorder, said he begged to differ.  Maybe half the cases, Roithmayr insisted, must be due to some as yet identified environmental factors.

Click here to read what every parent should know about autism.

Last January  Dr. Fred Volkmar, director of the Yale Child Study Center, created a far bigger controversy when the New York Times reported he had said new definitions of autism about to come from The American Psychiatric Association could effectively end the autism surge. ''We would nip it in the bud,'' the Times quoted Dr. Volkmar.

Related story: Better diagnosis, screening behind rise in autism

Volkmar was not available today, but I interviewed his colleague Dr. James McPartland, who did not back down from that view.

“People who might have been diagnosed with something else in the past are now being diagnosed with an autism spectrum disorder," McPartland said.  By “something else,” McPartland means problems that used to be labeled as ranging from “mental retardation” to “learning disabilities.”

“The way we diagnose autism spectrum disorder has changed,” McPartland continued.  “We're more inclusive. We include people with more cognitive ability and less severe problems then we have in the past.”

Anyone who spends time around children diagnosed on the “autistic spectrum” knows that it is indeed wide.  Many have the severe withdrawal and lack of ability to engage in social interactions that characterize classical autism.  But others seem high functioning and verbal.

Scientists have spent a lot of time looking for genetic changes that might account for disorders labeled as autism.  More than 500 genes have so far been implicated indicating that no clear genetic cause will be implicated.

As for environmental factors, there are strong suggestions that older parents, especially fathers can increase the risk as can multiple births. But none of that could account for more than a fraction of the enormous increase (78 per cent since 2002 when the CDC started tracing autism.)  The alleged association with childhood vaccinations has been widely discredited by scientists although a few hard core activists still cling to it.

So that takes us back to diagnosis.  Whatever it is called, there can be no doubt that a lot of kids need special attention – and the sooner they get it, the better off they are.  What a problem is called matters less than how society copes with it.