Improved diagnostic accuracy by using secondary ultrasound markers in the first-trimester screening for trisomies 21, 18 and 13 and Turner syndrome

Prenatal Diagnosis, 05/10/2012

The addition of secondary ultrasound markers (NB, DV and TR) to combined first–trimester screening showed a tendency toward improved accuracy of the screening.


  • Screening for aneuploidy was carried out in 4172 singleton pregnancies between January 2006 and December 2010.
  • Diagnostic accuracy of combined screening [inclusive of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta–human chorionic gonadotropin and pregnancy–associated plasma protein A] and of secondary ultrasound markers [NB, tricuspid regurgitation (TR) and Doppler studies of the DV] obtained at the same visit was assessed using the receiver operating characteristic (ROC) curve analysis.


  • The individual areas under the ROC curves of NT, NB, DV or TR ranged between 0.7 and 0.8, representing acceptable discrimination.
  • The area under the ROC curve of combined first–trimester screening was 0.87, whereas the addition of secondary ultrasound markers increased the area under the curve to 0.92, which represents excellent discrimination.
  • At a risk cutoff of 1:275, the detection rate for aneuploidy increased from 87% to 92% (z statistic=1.78, P=0.076), and the false positive rate decreased from 5.3% to 4.8%.

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