title: Fetal nasal bone hypoplasia in the second trimester: Comparison of diagnostic methods for predicting trisomy 21 (Down syndrome).
abstract: OBJECTIVE
  The aim of this prospective observational study was to identify the best method for use in diagnosing fetal nasal bone (NB) hypoplasia in the second trimester as a means of predicting trisomy 21 (Down syndrome).
  
  
  METHODS
  The NB length (NBL), NBL percentiles, and NBL multiple-of-median (MoM) values and the biparietal diameter-to-NBL ratios were calculated and compared in an attempt to identify the best predictive method and most appropriate cutoff value. Predictive values for several cutoff points were calculated. Receiver operating characteristic curves at a fixed 5% false-positive rate were used to compare the four methods.
  
  
  RESULTS
  NBL measurements were obtained from 2,211 (95.6%) of a total of 2,314 fetuses. Data from 1,689 of those 2,211 fetuses were used to obtain reference ranges, derive a linear regression equation, and calculate NBL percentiles and MoM values. Using a fixed 5% false-positive rate, we found 25.5% sensitivity for NBL (95% confidence interval [CI], 15-39.1) and 23.5% sensitivity for NBL percentiles (95% CI, 13.4-37), NBL MoM values (95% CI, 13.4-37), and biparietal diameter-to-NBL ratios (95% CI, 13.4-37).
  
  
  CONCLUSIONS
  Our study demonstrated that all four methods can be used in the second trimester for diagnosing fetal NB hypoplasia as a means of predicting trisomy 21 because their predictive values are similar at a fixed 5% false-positive rate. For simplicity of use, we recommend using 3 mm as the NBL cutoff value.
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Recep
authors.initials: R
authors.lastname: Has
authors.affiliation: Tekirdag Yasam Private Hospital, Tekirdag, Turkey.
authors.forename: Esra Gilbaz
authors.initials: EG
authors.lastname: Akel
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Ibrahim H
authors.initials: IH
authors.lastname: Kalelioglu
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Ozlem
authors.initials: O
authors.lastname: Dural
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Cenk
authors.initials: C
authors.lastname: Yasa
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Aytül Corbacioglu
authors.initials: AC
authors.lastname: Esmer
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Atıl
authors.initials: A
authors.lastname: Yuksel
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Alkan
authors.initials: A
authors.lastname: Yildirim
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Lemi
authors.initials: L
authors.lastname: Ibrahimoglu
authors.affiliation: Istanbul University, Istanbul Medical Faculty, Department of Obstetrics and Gynecology, Istanbul, Turkey.
authors.forename: Hayri
authors.initials: H
authors.lastname: Ermis
mesh_terms: D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D009295:Nasal Bone / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D064887:Observational Studies as Topic; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity
keywords: Down syndrome; nasal bone measurement; obstetrics; second trimester; trisomy 21; ultrasonography