Messages about genetic testing are everywhere these days: in the doctor’s office, in web ads, on television, in the news, and lots of other places. For members of the Jewish community whose heritage may put them at higher risk for genetic health issues, these messages seep into our consciousness, but often remain confusing. This short guide talks about the major categories of genetic testing you might encounter, what they’re for, and what they can and can’t tell you.

Ancestry testing and related health reports

Companies like Ancestry.com and 23andMe have made at-home, over-the-counter genetic testing for ancestry popular and relatively inexpensive. Ads that are services like this promise to share insights about where your ancestors came from, and by and large, they deliver. Depending on the company and test, the results you get back may provide information about one or both sides of your family.

These companies look to add value through other services, which might include connecting you to relatives or providing genealogical records. And increasingly, these companies offer optional health-related information along with their ancestry results.

Health information from such testing never comes with genetic counseling and is usually far too limited to be clinically useful. This type of testing is great for exploring your family’s roots, but should not be used to assess your health risks or make care decisions.

Carrier screening

In response to Tay-Sachs disease, Ashkenazi Jews in the United States were the first group to organize community carrier screening programs. When two people who are both carriers conceive, the child has a 1 in 4 chance of inheriting the disease. By identifying carrier couples and providing them with alternatives, the rate of Tay-Sachs births in the Jewish community quickly fell below the rate of the general population. Eventually, those tests evolved into genetic screening programs covering multiple diseases more common in the Jewish community, including Gaucher disease, Canavan disease, and others.

Today, many physicians and organizations offer what’s known as “universal” carrier screening: genetic tests that check carrier status for dozens or even hundreds of genetic diseases common among persons of multiple ethnic backgrounds. In Illinois, the Norton & Elaine Sarnoff Center for Jewish Genetics offers access to this type of testing for Jewish individuals and interfaith couples planning for their families.

The best time to get carrier screening is prior to conception, but the information received from testing and counseling can help expectant parents also.

Newborn screening

By law, every newborn in Illinois receives screening for a handful of genetic diseases, including several that are more common in the Jewish community. At birth, the hospital collects a few drops of blood and sends the samples to the state public health department for testing. Depending on when the results come back, parents receive follow up from the hospital, a pediatrician, or the state health department. If all tests are negative, parents receive no follow up.

Many, but not all, of the diseases on the newborn screening panel are also on universal carrier screening panels, but newborn screening is not a substitute for pre-conception or pre-natal carrier screening.

Every state has a newborn screening program similar to the one in Illinois, although testing methods and condition lists vary widely.

Hereditary cancer risk screening

Some of the most important recent advances in genetic testing relate to hereditary cancer risk. When appropriate, doctors and genetic counselors can order cancer genetic testing to determine whether or not a person has a gene mutation that increases their risk for different types of cancer. In the Jewish community, the most common of these mutations are in the BRCA1 and BRCA2 genes. BRCA mutations, which occur at a rate of 1 in 500 in the general population, are found in about 1 in 40 Jews of Ashkenazic descent, and can increase the risk of breast cancer in women and in men, ovarian cancer, prostate cancer, and pancreatic cancer.

However, hereditary cancer risk screening does not provide the whole picture of a person’s cancer risk. Only about 10 percent of cancer is hereditary, so a negative test does not mean a person has no risk for cancer. Similarly, a positive test does not mean a person is guaranteed to get cancer. For these reasons, the decision to pursue hereditary cancer risk screening should be made in consultation with a specialist physician or a genetic counselor. These professionals can also help guide a person through understanding positive test results and
their options.

Diagnostic and genomic testing

Some genetic testing has a very narrow purpose, either to help diagnose or rule out a specific genetic condition, or to gain insight into which treatments might be most effective for a particular form of a disease. For example, certain cancer variants respond better to specific types of chemotherapy, and doctors may order a genetic test of cancerous cells to determine the best course of treatment.

Getting help

If you need help understanding some aspect of genetic testing or genetic health visit the Norton & Elaine Sarnoff Center for Jewish Genetics website at jewishgenetics.org. In addition to providing a wealth of educational materials, the Sarnoff Center works with a genetic counselor from Insight Medical Genetics to help answer your questions and find the resources you need.

Jason Rothstein, MPH, is the director of the Norton & Elaine Sarnoff Center for Jewish Genetics, a supporting foundation of JUF, and is supported in part by the Michael Reese Health Trust.