Sequential and contingent prenatal screening for Down syndrome

OBJECTIVE: To compare the Integrated test in three policies for prenatal Down syndrome screening: Integrated screening for all women, sequential screening (first-trimester tests allowing early completion of screening for high-risk pregnancies), and Contingent screening (early completion of screening for high- and low-risk pregnancies). DESIGN AND METHODS: Estimation of detection rates (DRs) and false-positive rates (FPRs) using Monte Carlo simulation and cost effectiveness for each method. SETTING AND POPULATION: Down syndrome affected and unaffected pregnancies studied in the Serum Urine and Ultrasound Screening Study (SURUSS). RESULTS AND MAIN OUTCOMES: Integrated screening has the best screening performance. The performance of the other two policies approached that of Integrated screening as the first-trimester test FPR decreased. If the first-trimester FPR is set to 0.5% (risk >or= 1 in 30) with an overall DR of 90%, sequential and contingent screening yield overall FPRs of 2.25% and 2.42%, respectively, and 66% of the affected pregnancies are detected by the first-trimester test. The Integrated test on all women yields an FPR of 2.15%. With sequential screening, 99.5% of women would proceed to an Integrated test, or 30% with contingent screening if those with first-trimester test risks of