title: First trimester contingent test as a screening method for Down's syndrome. A prospective study in the general population.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Obstetrics and Gynaecology, Valme University Hospital, Seville, Spain. joseantoniosainz@hotmail.es
authors.forename: José A
authors.initials: JA
authors.lastname: Sainz
authors.forename: Rosa
authors.initials: R
authors.lastname: Serrano
authors.forename: Carlota
authors.initials: C
authors.lastname: Borrero
authors.forename: Enriqueta
authors.initials: E
authors.lastname: Turmo
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D020732:Cytogenetic Analysis; D004314:Down Syndrome / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008403:Mass Screening / Q000379:methods; D011153:Population; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood / Q000502:physiology; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies; D013030:Spain / Q000453:epidemiology
chemical_list: D015415:Biomarkers