April 26th, 2018

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Title:
Is It Possible to Improve Second Trimester Screening Efficacy with a Combined First and Second Trimester Nasal Bone Length Nomogram?
Authors:  Károly Szili, M.D., Melinda Vanya, M.D., Andrea Szabó, M.D., György Bártfai, M.D., Ph.D., D.Sc., and János Szabó, M.D., Ph.D., D.Sc.
  OBJECTIVE: To create a combined first- and second-trimester nasal bone length (NBL) nomogram in a large pregnant population and to investigate if the combined reference range affects the performance of ultrasound screening for trisomy 21 in the second trimester.

STUDY DESIGN: A reference range of fetal NBL was established on 2,508 singleton pregnancies examined at 14–28 gestational weeks. Screening performance for trisomy 21 was (prospectively) studied using the measurement values of fetal NBLs smaller than the 5th percentile as a cutoff value.

RESULTS: Trisomy 21 was found in 41 cases (1.6%). NBL measurement increased as a function of gestational age, showing almost linear relationship. Screening for trisomy 21 using the 5th percentile resulted in a sensitivity of 80.49% and specificity 98.17%, for a 1.83% false-positive rate. The likelihood ratio was 43.98. There were 41 trisomy 21 cases (1.6%). NBL measurement increased as a function of gestational age, showing almost linear relationship. Screening for trisomy 21 using the 5th percentile on the single and combined nomogram resulted in a sensitivity of 80.49% and specificity 98%, for a 1.83% false-positive rate, and the positive likelihood ratio was 43.98.

CONCLUSION: There was a significant difference between the two methods; combined nomograms had a higher performance as compared to the preliminary results in the literature. This study proved the importance of a population-specific nomogram and the increased screening performance by adding the first trimester NBL values to the second trimester nomogram.
Keywords:  Doppler ultrasonography; Doppler ultrasound; Doppler ultrasound imaging; Down syndrome; euploid fetus; midtrimester; nasal bone; nasal bone length; nomograms; pregnancy trimester, second; prenatal screening; trisomy 21
   
   
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