[New methods of prenatal screening for trisomy 21]

Area of Science:

• Genetics
• Prenatal Diagnostics

Context:

• Down syndrome (trisomy 21) is a leading genetic cause of intellectual disability.
• Maternal age has historically served as an initial screening indicator for Down syndrome risk.

Purpose:

• To review current and emerging screening strategies for Down syndrome.
• To evaluate the trade-offs between detection rates, false-positive rates, and early diagnosis.

Summary:

• Modern Down syndrome screening employs sonographic and maternal serum markers, significantly enhancing sensitivity and reducing false positives compared to older methods.
• The integrated test, combining first and second-trimester screenings, achieves an 85% detection rate with a 0.9% false-positive rate but delays diagnosis.
• Alternative strategies exist with comparable detection rates but potentially higher false-positive rates.

Impact:

• Highlights the need for coordinated national Down syndrome screening programs.
• Emphasizes the importance of sonographer training and quality assurance to standardize practices and improve outcomes.