title: Fetal nasal bone status in Chinese women undergoing first-trimester screening for trisomy 21.
abstract: OBJECTIVE
  The objective of the study was to determine the likelihood ratio for trisomy 21 in Chinese fetuses with absent nasal bone (NB) at 11-14 weeks of gestation.
  
  
  METHODS
  The NB was classified as present or absent in 8101 chromosomally/phenotypically normal or trisomy 21 pregnancies. The effect of crown rump length (CRL), nuchal translucency (NT), maternal age, and fetal karyotype on the incidence of absent NB was examined using logistic regression.
  
  
  RESULTS
  The NB was successfully examined in 7925 cases (97.8%). The incidence of absent NB in unaffected and trisomy 21 cases were 2.1% (164/7899) and 50% (13/26), respectively. CRL (odds ratio [OR], 0.9; 95% confidence interval [CI], 0.87-0.92), NT (OR, 1.7; 95% CI, 1.4-2.3), and trisomy 21 (OR, 22.3; 95% CI, 8.1-61) were significant independent predictors of likelihood of absent NB. Positive likelihood ratios (LR) for trisomy 21 in Chinese were lower than that of Caucasians for the equivalent CRL and NT measurements.
  
  
  CONCLUSIONS
  Estimated risk for trisomy 21 in Chinese incorporating nasal bone status should use LRs derived in Chinese rather than Caucasians.
authors.affiliation: Department of Obstetrics and Gynecology, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
authors.forename: Tak Yeung
authors.initials: TY
authors.lastname: Leung
authors.forename: Daljit
authors.initials: D
authors.lastname: Sahota
authors.forename: Lin Wai
authors.initials: LW
authors.lastname: Chan
authors.forename: Lai Wa
authors.initials: LW
authors.lastname: Law
authors.forename: Tak Yuen
authors.initials: TY
authors.lastname: Fung
authors.forename: Tze Kin
authors.initials: TK
authors.lastname: Lau
mesh_terms: D000328:Adult; D044466:Asian People; D002681:China; D004314:Down Syndrome / Q000175:diagnosis / Q000196:embryology*; D005260:Female; D006801:Humans; D007621:Karyotyping; D016013:Likelihood Functions; D008423:Maternal Age; D009295:Nasal Bone / Q000196:embryology*; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal