title: [Establishment and application of median serum markers for second trimester screening in Qingdao region].
abstract: OBJECTIVE
  To establish the median of serum markers for second trimester screening in Qingdao region and to assess the influence of median correction on the performance of screening.
  
  
  METHODS
  Maternal serum alpha-fetoproteins (AFP), human chorionic gonadotrophin, free beta subunit (β -HCG) and unconjugated oestriol (uE3) were assayed for prenatal screening of 18 188 singleton pregnancies at 15-20(+ 6) weeks gestation from January 2009 to July 2010. The median of serum markers was calculated based on above results and applied for risk estimation in screening for fetal aneuploidy from August 2010 to March 2011. The screening performance, specified in terms of detection rates (DRs), false positive rates (FPRs) and odds of being affected given a positive result (OAPR) were compared between the two groups. The risks of 45 affected pregnancies detected during the study were estimated with both Caucasian and corrected medians.
  
  
  RESULTS
  The average level of AFP in local pregnancies was similar to that of the Caucasian population, whilst β -HCG and uE3 were respectively 11% and 33% higher than those of Caucasians. The multiple of median (MoM) value was between 0.94 and 1.02 for the dataset based on the corrected median. At a cut-off of l in 270, FPR has decreased from 5.2% to 4.9%, and DR of Down syndrome has increased from 60% to 69.2%, and OAPR has increased from 1:79 to 1:59 when evaluating risk based on the corrected median. For the 45 affected pregnancies, three Down syndrome pregnancies could be missed because their risk estimates were lower than the cut-off level based on Caucasian median.
  
  
  CONCLUSIONS
  It is useful to establish and apply population and laboratory-specific medians in order to improve the performance of prenatal screening and diagnosis.
authors.affiliation: Department of Genetics, Qingdao Maternal and Children's Hospital, Qingdao, Shandong, People's Republic of China. yu_dongyi@yahoo.com.cn
authors.forename: Dong-yi
authors.initials: DY
authors.lastname: Yu
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
authors.forename: Nan
authors.initials: N
authors.lastname: Jiang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Hui-ying
authors.initials: HY
authors.lastname: Ren
authors.forename: Mei-yan
authors.initials: MY
authors.lastname: Han
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Shuo
authors.initials: S
authors.lastname: Li
authors.forename: Qi-qi
authors.initials: QQ
authors.lastname: Ouyang
authors.forename: Qun
authors.initials: Q
authors.lastname: Nie
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D004964:Estriol / Q000097:blood*; D005260:Female; D001556:Hexachlorocyclohexane / Q000097:blood*; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D000509:alpha-Fetoproteins; D001556:Hexachlorocyclohexane; D004964:Estriol; C023888:beta-hexachlorocyclohexane