When Angelina Jolie recently revealed that her decision to undergo a double mastectomy stemmed directly from the fact that she’d tested positive for a BRCA1 gene mutation—putting her at a nearly 90% risk of developing breast cancer—it turned genetic testing into a hot topic practically overnight

Ever since the human genome was unraveled a decade ago, research in the field of genetics has advanced at a breakneck speed. Ten years ago, you could take a test to find genetic links for about 900 diseases—today, that number is more than 2,500. And what was once considered an expensive procedure that could only be administered in a medical setting can now cost as little as $100 for a DNA test you can take at home.

But while it’s true that genetic testing can provide important information for diagnosing, treating and, in Jolie’s case, even preventing diseases, it’s not always clear which tests are really worth getting. So before you decide to follow the Hollywood starlet’s example, check out our guide to testing the genetic waters.

At-Home Kits

Want to find out if you’re at risk of developing osteoarthritis, psoriasis or celiac disease? Nowadays, anyone can unlock such secrets concealed within their DNA with an at-home kit. In fact, for just $99, you can purchase one online from the California-based personal genetics company 23andMe. Simply mail in a saliva sample, and six to eight weeks later, your genetic fortune is at your fingertips.

But proceed with caution: These direct-to-consumer tests only look at common markers, rather than read all of the variations in a gene, and they can be hard to fully interpret without additional input from a doctor or trained genetic counselor. And while the industry is expanding exponentially, the tests are poorly standardized, largely unregulated (none are FDA-approved) and typically not covered by insurance.

Doctor-Administered Tests

Legitimately concerned about your risk of developing cancer or diabetes? You can opt for a doctor-recommended screen based on factors like family history or ethnic background. While the tests can cost anywhere from $300 to $3,500, they’re generally covered by insurance. But check with your insurer first: Some require a letter from your doctor, a detailed family history or a visit to a genetic counselor (often covered by insurers) who’s trained to interpret the results.

There are many factors to consider before getting tested: emotional repercussions, cost and even insurance discrimination. According to the federal Genetic Information Nondiscrimination Act (GINA) passed in 2008, employers and health insurers cannot use information from genetic tests against you. But federal law doesn’t offer the same protection when it comes to long-term care, life and disability coverage.

Now that we’ve got the basics out of the way, here’s a look at three common genetic tests that doctors can offer patients—and their accompanying pros and cons.

Breast Cancer Testing

About 750,000 American women carry a mutation on a BRCA gene, which increases the lifetime odds of developing breast cancer from 12% to 60%. What’s more, BRCA mutations also increase a woman’s lifetime odds of developing ovarian cancer from 1.4% to between 15% and 40%. And it’s not just women who benefit from the test: BRCA2 mutations are also associated with an increased risk of prostate cancer, pancreatic cancer and male breast cancer.

Pros: A positive result can help you and your doctor create a preventive plan, including earlier and more frequent screenings or treatments. Knowing that you carry a BRCA mutation can also encourage family members to get tested too.
Cons: On the other hand, a negative result of a BRCA mutation can produce a false sense of security. Plus, genetic testing for cancer isn’t diagnostic—it can’t tell you whether or not you will develop cancer, only whether you carry a gene mutation that puts you at a higher risk. Likewise, negative test results don’t mean that you’re in the clear: Only 5% of breast cancers and 10% to 15% of ovarian cancers are caused by hereditary mutations in BRCA1 and BRCA2. In fact, many factors come into play when it comes to developing cancer, including inherited genes, haywire hormones and environmental effects.

Cost: Breast cancer genes have been a hotly contested topic. Myriad Genetics, the molecular diagnostic company that discovered the BRCA gene mutations, has been in the midst of a Supreme Court battle over their right to patent the genes—an act that has given them a virtual monopoly on the test since the 1990s.

Although Myriad’s test currently costs between $3,000 and $4,000, Peter Meldrum, the company’s president and chief executive, wrote in The New York Times that “the test remains widely reimbursed by insurance companies, with more than 95% of at-risk women covered and with an average out-of-pocket cost of about $100.”

In June, the Supreme Court ruled unanimously against Myriad, saying that isolated human genes can’t be patented—a decision that will open up testing to more genetic companies and likely lead to a significant fall in the price of the test.

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Alzheimer’s and Huntington’s Testing

The progressive form of presenile dementia known as Alzheimer’s and Huntington’s—a fatal neurodegenerative disorder that involves loss of motor control, personality changes, depression, dementia and death—are untreatable. For this reason, doctors generally discourage genetic testing for these diseases because the news can be shattering.

Pros: Huntington’s symptoms usually appear between the ages of 30 and 50, so knowing what the future holds might help a person tailor career choices, insurance coverage and family planning. Children of someone with Huntington’s have a 50/50 chance of also inheriting the disease, so many people choose to get tested before conceiving, as well as pursue preimplantation testing to prevent the disease from being passed down to the next generation.

Cons: While having the gene mutation for Huntington’s means that you’ll definitely develop the disease, finding markers of an elevated risk for late-onset Alzheimer’s doesn’t necessarily mean that you will come down with the disease. Since there is no cure or treatment for either disease, tests for Huntington’s and Alzheimer’s are only offered to adults—and always include pre- and post-genetic counseling sessions, as well as baseline neurological and psychiatric evaluations.

Cost: Depending on the lab, the tests can run anywhere from $300 to $1,500. Most insurance companies reimburse diagnostic testing, which confirms a diagnosis in a person who already has symptoms. Conversely, many carriers will not pay for predictive testing for a person without symptoms, especially in the case of Huntington’s and Alzheimer’s, since there is no medical action that can be done to prevent the condition.

When you’re considering the idea of having children, there are two types of genetic tests available to prospective parents.

Preconception tests can tell before a couple gets pregnant if either person carries a dominant gene for say, Huntington’s, or whether both people carry a recessive gene that could cause such conditions as cystic fibrosis and Tay-Sachs disease, a progressive deterioration of nerve cells that usually results in death by the age of four.

And prenatal testing helps expectant mothers—specifically those over 35 who are at higher risk of giving birth to kids with certain disorders—know whether an unborn child will have a genetic condition, such as muscular dystrophy, or a chromosomal disorder, like Down’s Syndrome.

Pros: During preconception testing, if you screen positive for a recessive genetic abnormality such as cystic fibrosis or Tay-Sachs disease but your partner doesn’t, your child will not inherit the condition—knowledge that can be invaluable for couples. And even if you both screen positive, there’s only a 25% chance that your baby will have the disease.

Preimplantation genetic diagnosis (PGD), a specific type of prenatal testing that uses such assisted reproductive techniques as in vitro fertilization, also helps to drastically reduce the risk of genetic or chromosomal disorders, since only embryos without alterations are implanted in the uterus.

Cons: Although complications are rare, prenatal testing carries a very small but real risk of miscarriage or maternal infection. Moreover, while prenatal testing carries a high degree of accuracy, it cannot identify all possible inherited disorders and birth defects.

Cost: Preconception testing costs less than $400, and it’s often covered by insurance. But the $13,000+ price of PGD is far from trivial, which includes the fee for IVF (an average $8,000 per cycle) and the cost of genetic testing, which is an estimated $2,000. Fewer than 15 states mandate insurance to cover IVF, but only in cases of infertility. For this reason, preimplantation IVF and its genetic component typically aren’t covered.

To Test or Not to Test

Until researchers find a cure for genetic diseases, testing may be the best way to assess and manage your risk factors for developing such conditions. But before you decide to take a look at your genetic makeup, gather as much information as you can about your family’s medical history—and consult a doctor or a genetic counselor (you can find one at nsgc.org) in order to fully understand the scientific, emotional and ethical factors surrounding the decision and the results.