On Tuesday, the FDA granted marketing authorization to 23andMe for a home DNA-testing kit that will let consumers find out whether they might have a mutation that puts them at higher risk of some types of cancer.

My colleagues and I who practice in this area were immediately concerned when we heard of this development.

Dr. Daniel Silver
Jefferson Health
Dr. Daniel Silver

Here's why: though you can learn some things from a mail-in kit, it's even more important to understand what these tests cannot tell you – and why that could make a big difference to your health.

Pursuing genetic testing is not an easy decision even if you know all the potential medical and personal implications of learning you do or don't have a mutation. 23andMe's newly approved test looks for only three BRCA1 and BRCA2 mutations—yet there are over 1,000 known mutations in these genes that can significantly raise the risk of several cancers.

What's more, we now know there are many other genes besides BRCA1 and BRCA2 that can cause elevated cancer risks.

Getting the all-clear from 23andMe  may falsely assure some people that they do not need to have physical exams or regular cancer screening tests such as mammograms, or that they do not need to even consider more comprehensive genetic testing. Some might even interpret such a test result as an overall clean bill of health now and in the future.

And for those who learn they do have one of the three mutations by the 23andMe test, what comes next? Will they know how to get the counseling they need to use this information constructively? Will they be devastated, believing they definitely will develop cancer (which is not, by the way, what these tests mean), and fail to take action to learn how to protect their health?

The $199 price tag of 23andMe's home kit may sound attractive. And it's true that not everyone's insurance will cover genetic testing. The National Comprehensive Cancer Network (NCCN) publishes a list of criteria to determine if genetic testing is medically necessary; most insurance companies use these criteria to determine coverage.

However, if you do not meet these criteria but still want genetic testing, talk to a health care professional. If testing makes sense for you, you may have to pay for the testing out of pocket, but there are more comprehensive genetic testing options that are comparable in price to 23andMe's kit.

Your doctor can help you understand all of the pluses and minuses of testing far more completely than you can learn from a home kit. And if you do decide on a more comprehensive genetic test, a trained health care professional can fully explain your unique results and help you assess what either a positive or negative result means to your own health care needs.

Daniel P. Silver, MD, PhD, leads the Breast Cancer Research Program at Jefferson Health's Sidney Kimmel Cancer Center.