What is Carrier Screening?
Carrier testingCarrier testing can determine if a person carries one of the altered genes that cause a recessive disease. DNA carrier testing establishes the presences or absences of particular mutation(s). Enzymatic testing evaluates the level of activity of an enzyme, which when absent causes disease. In some diseases the enzyme test is not sensitive enough to determine carrier status. More is a type of genetic testing done to find out if you carry a change in a geneOften referred to as the "unit of heredity." A gene is composed of a sequence of DNA required to produce a functional protein. More that can cause a specific genetic disease. Most often, being a carrier for one of these changes does not mean that you have the genetic disease yourself, but that you may have a chance to pass it on to a child.
Depending on the type of carrier screening, the test could use a sample of blood, saliva, or tissue from inside the cheek.
For Tay-Sachs carrier screening specifically, current data supports the use of a test called gene sequencing to identify whether an individual is a carrier. To learn more about this data and other kinds of screening tests, check out NTSAD’s 2019 position statement here.
Why is Carrier Screening Important?
It’s possible to carry a change in a gene for a genetic disease without any signs or symptoms.
When carrier screening is done before pregnancy, it helps you determine the chances of having a child with a rare genetic disease.
Anybody Can Be a Carrier
Every person carries two copies of each gene in their body, one inherited from each parent. Tay-Sachs, Canavan, GM1, and Sandhoff diseases are autosomal recessiveDescribes a trait or disorder requiring the presence of two copies of a gene mutation at a particular locus in order to express observable phenotype; specifically refers to genes on one of the 22 pairs of autosomes (non-sex chromosomes). More diseases. This means that a person must inherit two changes in the gene that causes the disease, one in each of their gene copies. Therefore, both parents must carry a change in the same gene to have a chance of both passing on those changes to an affected child.
If you and your partner are carriers for the same recessive disease, there’s a 25% chance that your child will be affected with the disease—even if you already have a child who is unaffected. If one or both parents are a carrier of a recessive disease, there is a 50% chance that your child will also be a carrier.
According to the National Institutes of Health (NIH), the carrier rates among the general United States population are:
- Tay-Sachs: 1 in 250 people
- Canavan: 1 in 300 people
- GM1: 1 in 250 people
- Sandhoff: 1 in 600 people
Prevalence of Tay-Sachs Disease
While anybody could be a carrier of Tay-Sachs, there is a higher prevalence of the disease among some populations.
About 1 in 27 people of Ashkenazi Jewish descent is a carrier of Tay-Sachs disease. If you have Ashkenazi heritage, it’s a good idea to be screened, even if your partner is not Jewish.
People of Irish, Cajun, French Canadian, and Pennsylvania Dutch heritage also experience higher levels of Tay-Sachs disease in their populations.
If someone in your family or your partner’s family has Tay-Sachs, Canavan, GM1, or Sandhoff disease, you may consider undergoing carrier screening.
There are several different types of carrier tests that are available.
If you have a specific family history of a genetic disease, you may be offered a targeted test to determine whether you are a carrier for that disease.
Expanded carrier screening is another kind of carrier test. It tests whether you are a carrier for many different genetic diseases, especially diseases where it is more common in the general population to be a carrier.
You may also hear about whole exome sequencing. This is a test that looks at all the genes in your body to see whether you carry any changes.
By the same token, if carrier screening shows that you or your partner are carriers of a rare disease, it is recommended to share this information with blood relatives, so they can decide if they wish to be tested.
Your genetic counselor or clinician can help to provide you with resources for sharing this information about your test results with blood relatives.
How to Start the Carrier Screening Process
If you’re interested in genetic carrier screening, you can mention it during an appointment with your healthcare provider or OB-GYN. Be sure to discuss your family history, any genetic disease in your family, and your ancestry. Your clinician or OB-GYN will be able to order carrier screening tests for you and your partner.
You can also ask them about a referral for an appointment with a genetic counselor or locate a genetic counselor directly (see below), who will collect your family history information and help order carrier screening.
Contact your health insurance company to ask:
- If it covers carrier screening
- If you need a clinician referral for a genetic counselor
How to Find a Genetic Counselor
A genetic counselor may collect your medical and family history, discuss your personal risks for genetic disease, and provide you with more information about carrier screening or other kinds of genetic tests. They will guide you through deciding about testing, help you understand the results, explain the options and resources available to you, and support you as you decide what to do next.
Depending on your health insurance, you may need a referral for a genetic counselor or you may be able to contact a genetic counselor directly.
Some genetic counselors support clients in person and others can provide their services virtually.
You can use the National Society of Genetic Counselors (NSGC) directory to find a genetic counselor in the United States.
Frequently Asked Questions
You are encouraged to talk to your healthcare provider or OB-GYN about carrier screening if you’re thinking about starting a family or if someone in your family has Tay-Sachs, Canavan, GM1, or Sandhoff disease.
For more information, please see our FAQ below or email Becky Benson (firstname.lastname@example.org), Family Services Manager or Diana Jussila (email@example.com), Director of Family Services.
Genetic Testing Terminology
Known Carrier of Tay-Sachs Disease
Other Issues of Concern