Growing complexity in the choice of Down's syndrome screening policy.

Abstract

In the past antenatal screening for Down’s syndrome was simple. It was merely a matter of referring for invasive prenatal diagnosis women of advanced reproductive age or with a family history of aneuploidy. The only policy question this raised was over the choice of cut-off age and consensus was quick to emerge, at least at a national level. But the subsequent discovery of several maternal serum and ultrasound markers has introduced considerable complexity. Policy makers today have to choose: the screening modality, biochemistry, ultrasound or both; the gestational period; the marker combination; and the cut-off level. This has spawned a widespread diversity in screening practice which is confusing both to patients and practitioners. It is possible to demonstrate that some policies will lead to the detection of more affected pregnancies for a given number of prenatal diagnoses, than others. Whilst predicted performance is not the sole arbiter of choice—there are considerations of practicality and cost to be made too—this is a useful starting point in policy decision-making.