Carrier Screening
Carrier screening is DNA testing to determine whether a couple are carriers of the trait for certain conditions and therefore are at risk for having a baby with the disease. The testing performed will focus on family history and ethnic background, based on what conditions are more frequently found among that group.
The screening should take place before conception so you are aware of your risks and can weigh your options with a genetic counselor. If you are already pregnant and have a carrier screening that shows you and your partner are both carriers of a condition, you may opt for diagnostic testing of the fetus such as an amniocentesis or Chorionic Villus Sampling (CVS) as a prenatal test used to test for chromosomal abnormalities and other genetic problems and determine whether two copies of the defective genes are present.
Carrier screening is performed through a blood or saliva test. One sample can be tested in the laboratory for numerous diseases. Testing can be conducted for many common diseases, including:
- Cystic fibrosis
- Sickle cell disease
- Thalassemia
- Tay-Sachs
- Familial dysautonomia
- Canavan disease
- Fragile X syndrome
- Gaucher disease
- Mucolipidosis IV
- Niemann-Pick disease type A
- Fanconi anemia group C
- Bloom syndrome
Since many people do not belong to a single ethnic group, a screening test will gather genetic information to evaluate for more than 90 recessive disorders.
Down Syndrome Screening
Another important form of carrier screening is testing for Trisomy 21, the most common cause of Down syndrome. The most frequently occurring chromosomal variation, Down syndrome is found in approximately one out of every 800 infants. Aside from family history, the age of the potential parents can be a factor. In other patients it is just a random genetic deviation.