Parental testing performed to assess carrier status for a specific genetic abnormality. Typically performed on DNA from a blood specimen to test for targeted mutations, but testing also can include other modalities such as enzymatic testing and gel electrophoresis.
Use
Carrier testing for autosomal recessive disease (may be targeted to specific ethnic groups). Examples:
CF: DNA testing for common mutations
Spinal muscular atrophy: DNA testing for common mutation
Sickle cell anemia: presence of sickling; confirmed by Hb electrophoresis
Tay-Sachs disease: enzyme activity
α-Thalassemia and Ž ²-thalassemia: decreased mean corpuscular volume; confirmed by Hb electrophoresis
Carrier testing for X-linked disease. Example:
Fragile X (DNA testing for premutation); not currently offered to general population
Limitations
DNA testing for common mutations does not eliminate the possibility that an individual carries a rare mutation not included in the screening panel. Therefore, even if testing is negative, a residual carrier risk remains. Residual risk depends on many factors, including disease prevalence, patient ethnicity, family history, and the number of mutations included in the screen.