Down syndrome screening in the first and/or second trimester: model predicted performance using meta-analysis parameters.

OBJECTIVE: To predict the screening performance for 17 policies currently in use or being considered for the near future.
METHODS: Multivariate Gaussian modeling using parameters derived from published meta-analyses and new meta-analyses for gestation-specific nuchal translucency and between trimester correlations.
RESULTS: For a 1% to 5% false-positive rate, first trimester screening achieved detection rates up to 16% to 25% higher than the best second trimester combination. Screening in both trimesters sequentially could yield an even greater increase in detection of 24% to 35%. The most efficient sequential policy was contingent screening, which has a high detection rate with only 15% of women needing second trimester tests.
CONCLUSION: Modeling with meta-analysis derived parameters provides a reliable guide for policy and favors a contingent screening policy. The widespread practice of calculating first and second trimester risks separately should be abandoned.