First trimester contingent test as a screening method for Down’s syndrome. A prospective study in the general population

Abstract

Objectives: To evaluate the possibility of implementing a contingent test as a screening method for Down’s syndrome (DS) in the first trimester of pregnancy, and assess its sensitivity (Sen) and false positive rate (FPR). Methods: Prospective study covering a 4-year study period (July 2006–June 2010). Pregnant women were offered a combined test (CT) as the first step of a contingent test. An intermediate risk group is identified in the CT (1/101 and 1/1000) and offered an ultrasound assessment of secondary s (nasal bone, ductus venosus, tricuspid regurgitation). Results: CTs were performed on 10,452 pregnant women (24 cases of DS). In the intermediate risk group, which had 7 cases of DS, we performed secondary ultrasound marker assessment on 98.1% (1,017/1,036). The CT and the contingent test had a Sen of 83% (95% CI; 67.9–98) (20/24) and 70.8% (95% CI; 52.6–88.9) (17/24) with an FPR of 3% (95% CI; 2.7–3.3) (316/10,430) and 2% (95% CI; 1.7–2.3) (220/10,408), respectively. Conclusions: With the contingent test, we managed to reduce the FPR, but the Sen was too low for use as a screening method for DS.

Keywords::

• Down Syndrome
• Prenatal screening
• ultrasound markers

Declaration of Interest: The authors report no conflicts of interest.