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Cross-trimester marker ratios in prenatal screening for Down syndrome
Nicholas J Wald1, Jonathan P Bestwick, Joan K Morris
1Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, Barts and the London Queen Mary's School of Medicine and Dentistry, UK. n.j.wald@qmul.ac.uk
Prenatal Diagnosis
|June 2, 2006
Summary
Adding cross-trimester ratios to integrated Down syndrome screening significantly improves detection rates and reduces false positives. This cost-effective enhancement makes prenatal screening safer and more effective for identifying Down syndrome pregnancies.
Area of Science:
- Prenatal diagnostics
- Biochemical screening
- Genetics
Background:
- Integrated screening combines first- and second-trimester measurements for Down syndrome detection.
- Cross-trimester (CT) ratios utilize serum marker levels from both trimesters.
- Existing screening methods have limitations in detection rates and false positives.
Purpose of the Study:
- To evaluate the performance of Integrated Down syndrome screening when CT ratios are incorporated.
- To assess the efficacy and cost-effectiveness of adding CT ratios to existing screening protocols.
Main Methods:
- Utilized data from the Serum Urine and Ultrasound Screening Study (SURUSS).
- Calculated CT ratios by dividing second-trimester marker concentrations by first-trimester concentrations.
- Employed Monte Carlo simulations to estimate screening efficacy and cost-effectiveness.
Main Results:
- Median CT ratios significantly differed between Down syndrome and unaffected pregnancies.
- Incorporating CT ratios reduced the false-positive rate by approximately two-thirds at a 90% detection rate.
- The addition of CT ratios did not increase the cost per detected Down syndrome case.
Conclusions:
- CT ratios substantially enhance the efficacy and safety of prenatal Down syndrome screening.
- The integration of CT ratios is a cost-effective strategy for improving screening programs.
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