Genetic Testing: Carrier Screening
What is carrier screening?
Carrier screening is an optional test that is available to those considering pregnancy. Some companies have designed panels to identify common changes, or mutations, in 23 different genes as recommended by ACOG. If a change is found, it increases the chance of that person having a baby with a health problem.
This test cannot determine if the baby actually has one of these conditions; instead it helps find couples that may be at a higher risk of having a baby with such a condition. If a higher risk is identified, further tests that can confirm or rule out these conditions are available.
- Noncarrier: A person that does not have any of the common gene changes.
- Carrier: A person with a single gene change. They do not have any medical problems, but have a higher chance of having a child with a problem.
All of the conditions tested for in carrier testing panels are inherited in an autosomal recessive manner, with the exception of Fragile X syndrome. This means that in order to have an affected child, both parents must be carriers. If both parents are carriers, their chance of having an affected child is 25 percent.
What does the test involve?
A blood sample is collected in a special tube, which is then mailed to a laboratory. There, DNA is isolated from the blood and analyzed for common changes that cause 23 different genetic disorders.
When will I get results? How are they reported?
The final results are available about 2-3 weeks after the sample is sent to the laboratory. Results are sent to your physician. Results are reported as either "carrier" or "noncarrier." If you are found to be a carrier for one or more conditions, you will have the option of setting up an appointment with the genetic counselor.
What do I need to do if the results show that I am a noncarrier?
When the results show that you do not have the common mutations in the disorders tested for, it reduces the chance that you will have a child with that disorder. Testing can never eliminate the chance for these disorders. Many people feel reassured by results that are normal. Other people might wish to further reduce their risk by having their partner tested for these disorders as well.
What if my results show that I am a carrier?
You will be contacted and given the option of setting up an appointment with the genetic counselor to review the results of the test if you are found to be a carrier for one more conditions. It is estimated that 20 percent of individuals taking this test will find that they are a carrier for at least one condition. However, the chance that both parents will be a carrier for the same condition is less than 1 percent. If your test shows that you are a carrier for a condition, then testing your partner for this disorder may refine the risk to a pregnancy. A test result that shows that you have one of the common mutations for a disorder means that you have a higher chance for a having a baby with that disorder, but it does not mean that a baby will definitely have that specific genetic condition.
What is tandem screening?
Tandem screening involves testing both partners at the same time. Tandem screening allows faster identification of at-risk couples. This is always an option for you.
What if I have a family history of a genetic disorder?
Patients/couples with a family history of any genetic condition should discuss testing options with their doctor and/or genetic counselor.
What is the accuracy of the test?
Carrier screening analyze common mutations in many different disorders. Since every ethnic group has certain genetic conditions which are more common, the detection rate will vary for each disorder.
Can all genetic conditions be detected by carrier screening?
No, no test can guarantee a child free of birth defects or learning problems.
Please feel free to contact us if you have any questions or concerns at (608) 824-6160.