Genetic Carrier Testing

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Subject: Genetic Carrier Testing

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Definition

  • 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 β-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.

 
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