Improved contingent screening strategy increased trisomy 21 detection rate in the second trimester

Area of Science:

• Prenatal diagnostics
• Biochemical screening
• Maternal-fetal medicine

Background:

• Second-trimester screening is crucial for identifying fetal aneuploidies.
• Optimizing screening protocols can enhance detection rates and cost-effectiveness.
• Trisomy 21 (Down syndrome) remains a primary concern in prenatal diagnostics.

Purpose of the Study:

• To establish optimal threshold values for biochemical markers in low-risk pregnancies during the second trimester.
• To develop enhanced contingent screening strategies for improved trisomy 21 detection.
• To assess the cost-effectiveness of the proposed screening modifications.

Main Methods:

• Analysis of singleton pregnancies undergoing second-trimester double, triple, or quadruple screening over six years.
• Determination of threshold values for free beta-hCG, AFP, and uE3 multiples of the median (MoM).
• Evaluation of detection rates, false negative rates, and cost-effectiveness of contingent screening.

Main Results:

• Defined thresholds: free β-hCG MoM ≥ 2.50, AFP MoM ≤ 0.50, or uE3 MoM ≤ 0.70 for low-risk designation.
• Contingent screening identified higher trisomy 21 detection rates (85.00% to 95.24%) with reduced costs (5.26% to 24.36%).
• Increased detection of trisomy 21 cases with false negatives in low-risk groups undergoing further non-invasive prenatal screening.

Conclusions:

• Implementing defined biochemical thresholds can enhance trisomy 21 detection in low-risk second-trimester pregnancies.
• This strategy improves the efficiency of prenatal testing and reduces overall screening expenses.
• Optimized screening protocols contribute to better maternal and fetal health outcomes.