title: Meta-analysis of first trimester Down syndrome screening studies: free beta-human chorionic gonadotropin significantly outperforms intact human chorionic gonadotropin in a multimarker protocol.
abstract: OBJECTIVE
  The purpose of this study was to compare free beta and intact human chorionic gonadotropin in first trimester screening with pregnancy-associated plasma protein-A and nuchal translucency.
  
  
  METHODS
  A Monte Carlo simulation trial was conducted based on a literature review of the PUBMED database (1966 to November 2005).
  
  
  RESULTS
  In younger patients (< 35 years), detection of Down syndrome increased by 4, 5, 6, and 7 percentage points when free beta was added to pregnancy-associated plasma protein-A and nuchal translucency compared with 0, 0, 2, and 4 percentage points for intact human chorionic gonadotropin at 9-12 weeks' gestation, respectively. In advanced maternal age patients (> or = 35), inclusion of free beta-human chorionic gonadotropin reduced the false-positive rate by 2.5, 3.1, 3.8, and 4.4 percentage points compared with 0.1, 0.3, 1.0, and 2.2 percentage points for intact human chorionic gonadotropin at 9-12 weeks, respectively.
  
  
  CONCLUSIONS
  The results of our analysis suggest that in a first-trimester Down syndrome screening protocol free beta-human chorionic gonadotropin achieves higher sensitivity and lower false-positive results than intact human chorionic gonadotropin . Moreover, intact human chorionic gonadotropin does not add substantially to screening performance until the end of the first trimester.
authors.affiliation: Comprehensive Genetics, and Mt Sinai School of Medicine, New York, NY 10021, USA. Evans@Compregen.com
authors.forename: Mark I
authors.initials: MI
authors.lastname: Evans
authors.forename: David A
authors.initials: DA
authors.lastname: Krantz
authors.forename: Terrence W
authors.initials: TW
authors.lastname: Hallahan
authors.forename: Robert S
authors.initials: RS
authors.lastname: Galen
mesh_terms: D015415:Biomarkers / Q000097:blood; D006063:Chorionic Gonadotropin / Q000097:blood*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D002985:Clinical Protocols; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A