title: Validity of different methods to prenatal screening for Down's syndrom during first and second trimester pregnancy of Chinese-women.
abstract: OBJECTIVE
  To identify and determine the optimal method to screening for fetal Down's syndrome (DS).
  
  
  METHODS
  Three large cohorts with 17 118, 39 903, 16 646 subjects were enrolled for the first trimester double marker (pregnancy-associated plasma protein A and free β-human chorionic gonadotropin) screening (FTDMS), second trimester double marker (α-fetoprotein and free β-human chorionic gonadotropin) screening (STDMS), and second trimester triple marker (α-fetoprotein, free β-human chorionic gonadotropin and unconjugated estriol 3) screening (STTMS), respectively. The sensitivity, specificity, false positive rate (FPR), false negative rate (FNR) and the areas under ROC curves (AUCs) were estimated in order to determine the optimal screening method in women under or above 35 years old.
  
  
  RESULTS
  For women under 35 years old, STTMS was the best method with a detection rate of 68.8% and FPR of 4.3% followed by the STDMS with a detection rate (sensitivity) of 66.7% and FPR of 4.9%. The FTDMS had a lower detection rate of 61.1% and FPR of 6.3%. For women above 35 years old, the detection rate of all the methods was similar, but STTMS method had a lowest FPR of 15.9%. For women under 35 years old AUCs were 0.77 (95% CI, 0.64 to 0.91), 0.81 (95% CI, 0.71 to 0.91), and 0.82 (95% CI, 0.69 to 0.96) for FTDMS, STDMS, and STTMS methods, respectively; for those above 35 years old, AUCs were 0.70 (95% CI, 0.56 to 0.83), 0.70 (95% CI, 0.59 to 0.82), 0.78 (95% CI, 0.58 to 0.97) for FTDMS, STDMS and STTMS , respectively.
  
  
  CONCLUSIONS
  Findings from our study revealed that STDMS is optimal for the detection of fetal DS in pregnant women aged under 35. For individual women, if economic condition permits, STTMS is the best choice, while for women aged above 35, STTMS is the best choice in this regard.
authors: Department of Epidemiology and Biostatistics, School of Public Health, Central South University, Changsha 410078, Hunan, China.
authors: Fang
authors: F
authors: Yang
authors: Hua
authors: H
authors: Wang
authors: Jing Cheng
authors: JC
authors: Shi
authors: Ming
authors: M
authors: Hu
mesh_terms: D000328:Adult; D044466:Asian People; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*
keywords: Down’s syndrome; First trimester, Second trimester; Marker; Prenatal screening