Types of Genetic Tests
There are many different types of genetic tests. Your doctor or genetic counselor can help you decide which genetic test is right for you after reviewing your personal and family medical history. In general, panel genetic testing (tests for many genetic mutations) is the most common genetic test done to determine breast cancer risk.
Targeted single variant testing
Single variant testing looks for just one specific mutation, or variant, in one gene. This type of test may be used when one family member has tested positive for a mutation in a particular gene, such as BRCA1, and another family member wants to have genetic testing to see if they also have this inherited mutation. If there is no known mutation in a family, single variant testing isn’t recommended.
Single gene testing
Single gene testing looks for mutations in just one gene. Your doctor or genetic counselor might recommend single gene testing if you or your child have symptoms of a condition that is linked to mutations in a specific gene, Duchenne muscular dystrophy or sickle cell disease, for example. Because mutations in several genes are linked to a higher risk of breast cancer, single gene testing isn’t commonly recommended for people who want information about breast cancer risk.
Panel genetic testing
Panel genetic testing looks for mutations in a number of genes linked to a disease. Because higher breast cancer risk is linked to mutations in several genes, including ATM, BRCA1, BRCA2, CDH1, CHEK2, PALB2, STK11, and TP53, among others, many doctors and genetic counselors commonly recommend panel testing to determine inherited breast cancer risk.
Whole genome or exome testing
These are large-scale tests that look for genetic mutations throughout a person’s genetic code or DNA.
Humans have 46 chromosomes in 23 pairs. A chromosome is a strand of tightly wound DNA. DNA is a sequence of chemical letters, nucleotides, and a particular sequence of nucleotides forms a gene.
In total, the human genome has approximately 3 billion pairs of nucleotides, which serve as the instruction manual for life. Interestingly enough, only about 1% of these 3 billion base pairs are coding, meaning they give instructions to the body. This 1% is called the exome. Researchers think that about 85% of all mutations that cause disease are found in the exome.
Exome sequencing looks for mutations in the exome.
Whole genome sequencing looks for changes in all the DNA, both coding and non-coding.
These tests are also called next-generation sequencing.
There are benefits and limitations when using these tests to find hereditary breast cancer risk. It’s a good idea to talk to your doctor or genetic counselor for more information.
Polygenic risk score testing
Polygenic risk score testing looks for genetic mutations that are very common in people known as single nucleotide polymorphisms, or SNPs (pronounced “snips”). A SNP is a single change in the building blocks of DNA (called nucleotides). While a SNP may only slightly increase a person’s risk of breast cancer, if someone has a large number of these SNPs, the small increases in risk can add up.
Researchers think that SNPs are the reason why breast cancer may be common in families that test negative for mutations linked to a higher risk of the disease, such as BRCA1 or BRCA2.
Polygenic risk score testing can look for more than 300 breast cancer-related SNPs and then assigns a level of risk based on the results.
Polygenic risk score testing isn’t yet recommended by National Comprehensive Cancer Network guidelines, but researchers are working to validate the tests and the accuracy of the results.
Listen to the episode of The Breastcancer.org Podcast featuring Drs. Holly Pederson and Elisha Hughes explain their research on a polygenic risk score test to predict the risk of triple-negative breast cancer in young Black women.
Predicting Triple-Negative Breast Cancer Risk in Young Black Women
Jun 1, 2024At-home genetic tests
At-home genetic tests — also called at-home DNA tests or ancestry DNA tests — allow you to swab your cheek yourself and send the sample in for analysis.
Some people like the idea of an at-home test because it may be more convenient and less expensive. Some at-home genetic tests cost less than $200, which may be less than the cost if you were to have genetic testing by your doctor.
But there are important things to consider before you decide to use an at-home test. In general, at-home tests don’t look for the same number of mutations and don’t look at as many genes as tests ordered in a clinic. So your results may be inaccurate, limited, or incomplete. For instance, a 2023 study found that at-home genetic tests miss more than 90% of BRCA mutations linked to cancer in people with no Ashkenazi Jewish (Eastern European) heritage.
Some companies require a doctor’s approval before sending an at-home genetic test and will even connect you with a doctor if you don’t have one, as well as with a genetic counselor to help you understand the results. But other at-home tests don’t require a doctor or genetic counselor to be involved at all, so you’re left on your own to understand the results. This can be difficult if the results are unclear or show that you have a mutation linked to breast cancer.
Whatever type of genetic test you choose, it’s important to understand which mutations are included in the test and what the results might mean, says genetic counselor Cristina Nixon.
“[B]e aware of what you’re being tested for ahead of time. Don’t just do the test, but actually talk to somebody about what this test has included and what the results might mean,” Nixon said. “You need to be aware of what the implications are should one of the genes come back positive [for a mutation].”
Listen to the episode of The Breastcancer.org Podcast featuring Cristina Nixon discussing the benefits and drawbacks of at-home genetic tests.
Benefits and Drawbacks of At-Home Genetic Tests
Mar 20, 2018— Last updated on December 12, 2024 at 9:22 PM