title: Contingent triple-screening for Down syndrome in the second trimester: a feasibility study in Mainland Chinese population.
abstract: OBJECTIVE
  To explore the efficacy of contingent triple-screening for Down syndrome (DS), that is, performing triple-screening in pregnant women with DS risks between 1/270 and 1/1000 at routine double-screening, in a Mainland Chinese population.
  
  
  METHODS
  Maternal serum concentrations of alpha fetoprotein (AFP), free-beta human chorionic gonadotropin (free beta-hCG), and unconjugated estriol (uE3) were measured by time-resolved fluoroimmunoassay in 24 double-screening false-negative (DSFN) and 322 double-screening true-negative (DSTN) pregnancies with DS risks between 1/270 and 1/1000 at routine double-screening performed at 15-20 weeks' gestation. DS risk of each pregnancy was calculated by computer software. The detection rate (DR), false-positive rate (FPR), and costs of contingent triple-screening were calculated and compared with routine double-screening methods.
  
  
  RESULTS
  Six of 24 DSFN and 3 of 322 DSTN were contingent triple-screening positive. Compared with routine double-screening, DR of contingent triple-screening increased by 10% (from 50% to 60%) without a significant increase of FPR (p > 0.05). When compared with routine triple-screening, uE3 costs in contingent triple-screening were reduced by more than 84.3%.
  
  
  CONCLUSIONS
  Second-trimester maternal serum contingent triple-screening could be effective and suitable for prenatal care in Mainland China. Governments and Health Agencies of other developing countries may also find this strategy cost-effective.
authors.affiliation: Women's Hospital, School of Medicine, Zhejiang University, No. 2 Xueshi Road, Hangzhou, China.
authors.forename: Zhenwei
authors.initials: Z
authors.lastname: Xie
authors.forename: Shiming
authors.initials: S
authors.lastname: Lu
authors.forename: Hui
authors.initials: H
authors.lastname: Li
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D002681:China / Q000453:epidemiology; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D004964:Estriol / Q000097:blood; D005260:Female; D005820:Genetic Testing; D005865:Gestational Age; D006801:Humans; D008403:Mass Screening / Q000191:economics / Q000379:methods*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000509:alpha-Fetoproteins; D004964:Estriol