title: Ductus venosus pulsatility index as an antenatal screening marker for Down's syndrome: use with the Combined and Integrated tests.
abstract: OBJECTIVE
  To assess the value of ductus venosus blood flow (expressed as pulsatility index, DVPI) in antenatal Down's syndrome screening when used with the Combined and Integrated tests.
  
  
  METHODS
  DVPI measurements between 10 and 13 weeks' gestation in 66 Down's syndrome and 7184 unaffected pregnancies were collected from women attending the Hospital Clinic, Barcelona, for antenatal care from 1999 to 2007 and combined with the Serum Urine and Ultrasound Screening Study (SURUSS) data to model screening performance, safety and cost-effectiveness of the screening tests with and without DVPI.
  
  
  RESULTS
  The median DVPI multiple of the normal median in Down's syndrome pregnancies was 1.55 (95% CI 1.36-1.73). As a single screening marker without using maternal age, DVPI has a 62% detection rate for a 5% false-positive rate. At a 90% detection rate (first trimester measurements at 11 weeks' gestation) the addition of DVPI reduced the false-positive rate of the Combined test from 8.5% to 4.6% and the Integrated test from 2.0% to 1.1%, with a corresponding reduction in fetal losses from diagnostic procedures. There was no material loss of cost-effectiveness.
  
  
  CONCLUSIONS
  Addition of DVPI measurements to the Combined and Integrated tests substantially improves the efficacy and safety of antenatal Down's syndrome screening.
authors.affiliation: Prenatal Diagnosis Unit, Institute of Gynecology, Obstetrics and Neonataology, Hospital Clinic Barcelona - Maternitat Campus, University of Barcelona Medical School, Barcelona, Spain. ABORRELL@clinic.ub.es
authors.forename: A
authors.initials: A
authors.lastname: Borrell
authors.forename: V
authors.initials: V
authors.lastname: Borobio
authors.forename: J P
authors.initials: JP
authors.lastname: Bestwick
authors.forename: N J
authors.initials: NJ
authors.lastname: Wald
mesh_terms: D015415:Biomarkers / Q000097:blood*; D001783:Blood Flow Velocity / Q000502:physiology; D004314:Down Syndrome / Q000097:blood* / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D014682:Vena Cava, Inferior
chemical_list: D015415:Biomarkers