title: [Second trimester maternal serum screening for Down's syndrome in women of advanced maternal age: a multi-center prospective study].
abstract: OBJECTIVE
  To evaluate the performance characteristics of the second trimester double test for the detection of fetal Down's syndrome (DS) in women of advanced maternal age (AMA).
  
  
  METHODS
  We undertook a prospective nation-wide multi-centered study and chose alpha-fetoprotein (AFP) and free beta-subunit of human chorionic gonadotrophin (free beta-hCG) as the serum markers. Between May 2004 and September 2006, 12 centers participated in the collection and analysis of maternal serum AFP and free beta-hCG. Patients with an increased risk of DS (> or = 1/270) were offered genetic amniocentesis. Follow up of the outcome of all pregnancies was obtained. Patients were divided into two groups, the AMA group and the non-AMA group and the screening efficiency was evaluated in both groups.
  
  
  RESULTS
  A total of 66 132 singleton pregnancies were included in the study, and there were 3610 (5.46%) AMA women. The median maternal age of AMA women was 36.8years (35 - 47 years). At a cut-off of 1/270, in the AMA group, the number of positive cases screened was 727 and 22 cases of fetal DS were detected; the number of negative cases screened was 2883, and no fetal DS was found. In the non-AMA group, the number of positive cases screened was 4743 and 69 cases of fetal DS were detected; the number of negative cases screened was 57 779, and 6 cases of fetal DS were diagnosed postnatally. In AMA group, the detection rate (DR), false positive rate (FPR) and odds of being affected given a positive result (OAPR) were 100%, 19.7% and 3.0% respectively. In the non-AMA group, the DR, FPR and OAPR were 92.0%, 7.5% and 1.5% respectively.
  
  
  CONCLUSIONS
  The double-marker test using AFP and free beta-hCG is an effective screen strategy for second-trimester detection of Down syndrome in AMA women.
authors.affiliation: Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Qing-Wei
authors.initials: QW
authors.lastname: Qi
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Jiang
authors.forename: Jun-Tao
authors.initials: JT
authors.lastname: Liu
authors.forename: Xu-Ming
authors.initials: XM
authors.lastname: Bian
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Shi-Ming
authors.initials: SM
authors.lastname: Lü
authors.forename: Bao-Sheng
authors.initials: BS
authors.lastname: Zhu
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.forename: Zheng-Feng
authors.initials: ZF
authors.lastname: Xu
authors.forename: Xiao-Ying
authors.initials: XY
authors.lastname: Pan
authors.forename: Yan
authors.initials: Y
authors.lastname: Cai
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D005315:Fetal Diseases / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D008403:Mass Screening / Q000379:methods; D008423:Maternal Age; D008875:Middle Aged; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies; D055815:Young Adult; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000509:alpha-Fetoproteins