Ask the Harvard Experts: Will a Genetic Test Predict My Disease Risk?

Ask the Harvard Experts: Will a Genetic Test Predict My Disease Risk?

Q: I am considering ordering a genetic test to see if I am at risk for cancer or Alzheimer’s disease. What are the pros and cons?

A: That’s a question many people are asking now that the FDA has given the green light to third-party direct-to-consumer (DTC) test kits that look for genetic risk information.

A DTC genetic test is a sort of do-it-yourself genetic fact finder. The tests, which cost a few hundred dollars, are not covered by insurance, and the results are delivered directly to you.

The test kit is shipped to you, with instructions. In the privacy of your home, you collect cells — typically, using either a cheek swab or a saliva collection tube — and then send them to a lab. The test results are usually posted on a secure website, where you view your information.

DTC tests can accurately detect genetic markers that increase disease risk. But being at increased risk for a disease doesn’t mean you will definitely get the disease. For example, if most people have a one-in-a-thousand chance of getting a disease, but you have a marker that triples your risk, that means your risk is three in a thousand — still a very low risk.

There are thousands of markers that indicate you are at increased risk for different conditions, but they don’t perfectly predict whether you will get those conditions. For example, if you have one copy of the APOE4 gene marker, it triples your risk for developing Alzheimer’s disease.

Likewise, if you carry a certain marker within the LRRK2 gene, it increases your risk for developing Parkinson’s disease two to three times. Still, many people with these genetic markers do not get the diseases for which they are at increased risk.

In contrast, some genetic markers indicate you are at very high risk. If you have one of the classic BRCA1 mutations, and you live long enough, you have a 60% to 70% chance of developing breast or ovarian cancer.

Before ordering a genetic test, be sure that you really want to know the results, and whether you would make changes in your life based on the findings. If you do decide to order a genetic test, it’s best to choose one that is FDA-approved, and provides a very clear explanation of the results.

Share the results of your genetic test with your primary care doctor. If the results suggest a higher than average risk of a particular disease, your doctor can advise you on ways to lower the risk. On the other hand, a test result showing a lower than average risk might falsely reassure you and lead to paying less attention to a healthy lifestyle.

(Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit