Combining first and second trimester markers for Down syndrome screening: think twice

Area of Science:

• Prenatal diagnostics
• Maternal-fetal medicine
• Genetics

Background:

• Down syndrome screening is crucial for identifying pregnancies at risk.
• Various screening strategies exist, each with different performance characteristics and practical implications.

Purpose of the Study:

• To compare the effectiveness of different Down syndrome screening strategies.
• To evaluate the practical considerations of implementing various screening protocols.

Main Methods:

• Performance characteristics of screening strategies were assessed using large datasets.
• Data included first and second trimester pregnancies, with and without Down syndrome.

Main Results:

• Integrated screening achieved 91% detection with a 2.5% false positive rate.
• Contingent and sequential protocols showed 82-91% detection with 2.6-2.9% false positives.
• Integrated and sequential protocols require extensive retesting in the second trimester.

Conclusions:

• Combining markers improves at-risk population definition but complicates management.
• Integrated protocols may not be ideal as primary screening strategies.
• Refining current programs with improved access and new markers is suggested over widespread integrated screening.