New contingent sequential screening model for Down syndrome based on the combined test associated with modified genetic sonography.

Objective: The aim of this study is to evaluate the possibility of implementing a contingent sequential screening test for Down syndrome (DS) based on the combined test (CT) associated with modified genetic sonography (MGS). We evaluate sensitivity (Sen), false positive rate (FPR), and economic costs.

Method: We compiled data from the results of a prospective screening programme for DS during a 5-year study period (July 2005-December 2011).