Importance of the integrated test in the Down's syndrome screening algorithm

Area of Science:

• Prenatal diagnostics
• Genetics
• Obstetrics

Background:

• Over 97% of pregnant women in the Czech Republic undergo antenatal screening for Down's syndrome.
• Pregnancy termination occurs in 95% of confirmed fetal chromosomal abnormalities.
• The first trimester combined test is the most common screening method.

Purpose of the Study:

• To evaluate the impact of an integrated sequential test on Down's syndrome detection rates.
• To enhance the accuracy of antenatal screening for fetal chromosomal abnormalities.

Main Methods:

• Analysis of anonymized data from a large antenatal care center (2010-2015).
• Inclusion of data on congenital defects, births, and terminated pregnancies from the National Registry of Congenital Anomalies.
• Comparison of first trimester combined test results with integrated sequential test outcomes.

Main Results:

• 600 Down's syndrome cases diagnosed (5.7 per 1000 births), 90% antenatally.
• 80% of antenatally detected cases were indicated by multimarker screening.
• Integrated sequential testing identified additional Down's syndrome cases missed by first trimester screening (6.25%).

Conclusions:

• An integrated sequential test detects 80-85% of Down's syndrome fetuses in the first trimester.
• An additional 5-10% of Down's syndrome pregnancies are detected in the second trimester with this integrated approach.
• These findings support the implementation of integrated sequential testing in national antenatal screening programs.