title: Second trimester prenatal screening for Down's syndrome in Mainland Chinese subjects using double-marker analysis of α-fetoprotein and β-human chorionic gonadotropin combined with measurement of nuchal fold thickness.
abstract: BACKGROUND
  This study examines the effectiveness of double-marker analysis for α-fetoprotein (AFP) and β-human chorionic gonadotropin (β-hCG) combined with measurement of nuchal fold thickness (NT) in the detection of Down's syndrome (DS) in Mainland Chinese subjects during second trimester prenatal screening.
  
  
  METHODS
  We examined pregnant women with a singleton pregnancy between 15 and 21 weeks of gestation who underwent second trimester screening for DS using double-marker analysis for AFP and β-hCG combined with ultrasound measurement of NT. The combined risk of DS was calculated. A cut-off of 1/270 was used to define a pregnancy at high-risk of DS. Amniocentesis was offered to all patients with high-risk pregnancies.
  
  
  RESULTS
  Using double-marker analysis for AFP and β-hCG in combination with measurement of NT, the detection rate of DS increased from 66.7% to 77.8% when compared with double-marker analysis alone with similar false-positive rates (4.35%, 4.83% respectively). Using receiver operating characteristic curve (ROC) analysis, we determined that the double-marker analysis combined with measurement of NT exhibited an increased area under the curve (AUC) of 0.835 (95% CI: 0.743 to 0.927) when compared to double-marker analysis alone, which had an AUC of 0.748 (95% CI: 0.635 to 0.860). In addition, both methods were more effective than any other single test such as AFP, free β-hCG or NT measurement.
  
  
  CONCLUSIONS
  Second trimester prenatal screening using double-marker analysis for AFP and β-hCG combined with measurement of NT is effective for the detection of DS in Mainland Chinese pregnancies.
authors.affiliation: Department of Clinical Laboratory, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China. iu_fang0126@yahoo.com.cn
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Hongyan
authors.initials: H
authors.lastname: Liang
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Jiang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Xue
authors.forename: Chun
authors.initials: C
authors.lastname: Yang
authors.forename: Jing
authors.initials: J
authors.lastname: Cheng
authors.forename: Peijia
authors.initials: P
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Guo
mesh_terms: D000328:Adult; D015415:Biomarkers; D002681:China; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D005865:Gestational Age; D006801:Humans; D008403:Mass Screening; D048208:Nuchal Translucency Measurement / Q000379:methods*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis; D018570:Risk Assessment; D055815:Young Adult; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000509:alpha-Fetoproteins