title: Biochemical screening for Down syndrome.
abstract: Maternal serum screening for Down syndrome is an established practise in many countries. In the second trimester human chorionic gonadotrophin (hCG) or free beta-hCG is the marker of first choice, with alpha-fetoprotein (AFP) as the second marker and unconjugated oestriol (uE(3)) the third. Statistical models with parameters derived by meta-analysis predict that a three marker combination will yield a 67% detection rate for a 5% false-positive rate. The model prediction have been confirmed in 21 large prospective intervention studies. A fourth marker, inhibin A, increases the detection rate by 7% for the same false-positive rate. In the first trimester, similar models predict that a combination of pregnancy associated plasma protein A, free beta-hCG, AFP and uE(3) will yield a 70% detection rate. This is increased to 88% if ultrasound nuchal translucency is used as an additional marker. Screening can also be extended to Edwards' syndrome, yielding high detection rates with little increase in the false-positive rate. Abnormal marker levels are also associated with a variety of adverse outcomes of pregnancy. High quality information and decision aids are needed to minimise anxiety among screenees.
authors.affiliation: Reproductive Epidemiology, Centre for Reproduction, Growth and Development, School of Medicine, University of Leeds, 26 Clarendon Road, LS2 9NZ, Leeds, UK. h.s.cuckle@leeds.ac.uk
authors.forename: H
authors.initials: H
authors.lastname: Cuckle
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis*; D004964:Estriol / Q000097:blood; D005260:Female; D006801:Humans; D008423:Maternal Age; D009436:Neural Tube Defects / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis / Q000652:urine; D011296:Prenatal Diagnosis / Q000379:methods*; D014427:Twins; D014463:Ultrasonography; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000509:alpha-Fetoproteins; D011266:Pregnancy-Associated Plasma Protein-A; D004964:Estriol