HealthDay News — Four methods can be used for diagnosing fetal nasal bone (NB) hypoplasia in the second trimester in order to predict Down’s syndrome, according to a study published online in the February issue of the Journal of Clinical Ultrasound.

Recep Has, MD, from Istanbul University, and colleagues examined the best method for use in diagnosing fetal NB hypoplasia in the second trimester as a means of predicting trisomy 21. They calculated and compared NB length (NBL), NBL percentiles, NBL multiple-of-median (MoM) values, and biparietal diameter-to-NBL ratios, and assessed predictive values for several cut-off points using data from 1,689 fetuses.

The researchers found that NBL had 25.5% sensitivity using a fixed 5% false-positive rate. Sensitivity for NBL percentiles, NBL MoM values, and biparietal diameter-to-NBL ratios was 23.5%.

“Our study demonstrated that all 4 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,” the authors write. “For simplicity of use, we recommend using 3 mm as the NBL cut-off value.”

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