Screening performance of different methods defining fetal nasal bone hypoplasia as a single and combined marker for the detection of trisomy 21 in the second trimester.

AbstractObjective: To evaluate different methods of defining fetal nasal bone hypoplasia in the second trimester for the detection of trisomy 21.Methods: Prospective study in Greek women undergoing anomaly scan between 18 + 0 and 23 + 6 weeks. The following methods of defining nasal bone hypoplasia were evaluated, either as a single marker or in combination with others: (1) BPD to nasal bone length (NBL) ratio; (2) multiples of the median (MoM) of NBL, according to normal curves from a Greek population; (3–4) NBL < 2.5 percentile according to normal curves (3) commonly used internationally curves and (4) curves from a Greek population.Results: In total, 1301 singleton fetuses were evaluated − 10 with trisomy 21. The best detection rate of trisomy 21 was achieved when the applied method was nasal bone percentiles adjusted to maternal ethnicity, in combination with other markers (<2.5 percentile according to normal curves from a Greek population; p < 0.001; sensitivity 50%; specificity 94.8%; false-positive...