(The Wall Street Journal) ¿ What are the chances that you will get heart disease, or Alzheimer's? Or that you'll get fat?

New genetic tests will soon be available to offer people answers to these questions and more, assessing their risk for a range of conditions based on a sample of saliva. It's one of the promises of the genetics revolution: Putting personalized medical information directly into the hands of individuals so they can make informed choices about their health.

Yet despite the potential, there are several reasons people might not yet embrace such tests — including skepticism about their scientific soundness, steep prices and insurance and privacy issues. Indeed, many genetic experts believe predictive gene-based tests aren't ready for wide use. Besides questions about accuracy, there is also the issue of how useful the answers will be.

There's no evidence, many physicians say, that people will act on such information to lead healthier lives. Little is known about the interplay of genetic and nongenetic factors such as diet, exercise, smoking and pollution that also affect a person's risk for disease.

And few doctors are well-versed in how to interpret genetic tests or what to tell patients based on the results.

One such test is set to be announced Tuesday by Navigenics Inc. of Redwood Shores, Calif. Called Health Compass, the test will be available starting early next year and will be offered directly to consumers via the Internet — circumventing the traditional doctor-patient relationship.

The company believes people will want to take the $2,500 test when they're healthy, and then make lifestyle and other changes to avoid or delay disease.

Results, which will be posted on a Web site that customers access with a password, will tell consumers their risk for more than 20 conditions, including diabetes, obesity, prostate cancer and glaucoma. Consumers would learn how their risk compares with the general population's, and what strategies they can follow to possibly reduce their chances of developing it.

"When you're reading your genetic risk and you realize that you might get this disease, that's when it's real and relevant," says Mari Baker, chief executive of the San Francisco-based start-up.

For consumers, the test will say: "What I might get and what I might start doing today so I don't get it in the future."

Another company, 23andme Inc. of Mountain View, Calif., is working on a similar direct-to-consumer test that outsiders say will provide gene-based ancestry and health-related information.

The company is not providing details until it is ready to launch the product, possibly by the end of the year. These tests are part of larger rush to capitalize on the growing body of genetic information that has been emerging since scientists finished mapping the human genome.

Silicon Valley venture-capital firms Kleiner, Perkins, Caufield & Byers and Sequoia Capital are among Navigenics' backer, while biotech giant Genentech Inc. and Google Inc. are among those financing 23andme.

Some 1,400 genetic tests are already on the market, but the vast majority focus on single genes associated with generally rare conditions. Some help assess the risk that a child will be born with a birth defect. Myriad Genetics Inc. markets tests for mutations known as BRCA1 and BRCA2 that are linked to a very high risk of breast and ovarian cancers.

More recently, deCode Genetics Inc. of Iceland launched two tests based on genetic variants that increase risk for heart attacks and a common heart-beat disorder called atrial fibrillation.

Like deCode, Navigenics' test focuses not on rare, single-gene diseases but on widely prevalent illness that have multiple genetic causes and that account for the biggest portion by far of human disease. But many genetics experts note there aren't any studies that connect use of such tests to improved health.

One concern is that results might encourage consumers to seek unnecessary and expensive follow-up tests to look for problems that aren't there, or despair that they can't do anything about their genetic fate.

Because the catalog of genetic variants linked to disease isn't complete, consumers could also receive a falsely reassuring clean bill of health.

"Progress in this field is extremely encouraging, but it's premature for this kind of test to be offered," says David Valle, director of the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins School of Medicine in Baltimore.

"For the most part, it is too early for the tests to have any meaningful impact on the current practice of medicine."

Behind the Navigenics test is an explosion in the discovery of gene variants known as SNPs, or single nucleotide polymorphisms, tiny alterations in the alphabet of our DNA that can result in differences in how people are predisposed to or protected from disease. But scientists believe multiple SNPs figure in predisposing people to most common illnesses. Typically, the role a single mutation plays is modest, involving interaction with other SNPs and a person's living habits.

"We don't have an understanding of how these things work yet," says Kathy Hudson, director of the Genetics and Public Policy Center at Johns Hopkins University.

Navigenics officials and their advisers acknowledge that much remains to be learned about SNPs and disease risk, but they say that links between certain variants and about 20 diseases are now sufficiently validated in multiple studies to provide consumers with useful information.

"The genie is out of the bottle," says John Doerr, partner at Kleiner Perkins, one of Navigenics' principal investors. Advances in genetic research and the Internet's role in empowering people to learn about their health are poised to change the health-care landscape, he says.

The plan is for consumers to order a test kit online, then send a saliva sample to Affymetrix Inc., the California-based developer of a gene chip that can sort through a million SNPs at once.

Affymetrix will forward findings to Navigenics, which will do further analysis and post the results on a secure Web site.

The $2,500 fee for the test will also cover consultations with a genetic counselor and a year of updates as more SNPs and diseases are validated and added to the test.

Annual subscriptions for additional updates will be available for about $250. David Agus, a cancer researcher at Cedars-Sinai Medical Center in Los Angeles who is a co-founder of the company, says he took the test and found he had a 68 percent risk of having a heart attack in his lifetime, compared with about 40 percent in the general population.

His kids, he says, now help him stay away from French fries. "I'm a believer in empowerment," he says.

One possible impediment to consumer interest is cost. Health insurers aren't likely to cover the tests until studies prove their value and link them to improved health.

That means — for the near term, at least — that relatively affluent consumers or early adopters of new technology are likely to be the main customers.