Diagnostic value of nuchal translucency thickness and facial profile ultrasonic markers for trisomy 21 syndrome in the first-trimester fetuses / 中华超声影像学杂志

ABSTRACT

Objective To retrospectively assess the diagnostic value of nuchal translucency (NT) thickness and facial profile ultrasonic markers [including frontomaxillary facial (FMF) angle,and the ratio of prenasal thickness to nasal bone length (PT/NBL)] for trisomy 21 syndrome in first-trimester fetuses.Methods Ultrasonograhic images of 35 fetuses with trisomy 21 syndrome and 70 gestational age matched normal fetuses were analyzed in first-trimester.NT,FMF angle and the PT/NBL ratio were measured retrospectively in stored images from digital database between January 2012 and December 2015.The diagnostic value of NT,FMF angle and PT/NBL ratio were compared with different combinations.Results (1) The mean NT was significantly higher in the trisomy 21 group than that in controls (t =7.401,P =0.00).The NT above 2.5mm was observed in 20 trisomy 21 fetuses (57.1％) and in 3 normal fetuses (4.3％).(2) The mean FMF angle was significantly higher in the trisomy 21 group than that in controls (t =-5.283,P =0.00).The FMF angle above the 95th percentile (93.6°) was observed in 13 trisomy 21 fetuses (37.1％) and in 1 normal fetus (1.4％).(3) The mean PT/NBL ratio was significantly higher in the trisomy 21 group than that in controls (t =-7.826,P =0.00).The PT/NBL ratio above the 95th percentile (0.93) was observed in 19 trisomy 21 fetuses (54.3％) and in 4 normal fetuses (5.7％).(4) The sensitivity and Youden index for trisomy 21 increased gradually,which were 57.1 ％ and 0.528 by using NT,and 74.3％ and 0.686 by using NT and FMF angle,and 91.4％ and 0.828 by using NT,FMF angle and PT/NBL ratio.There were significant differences in the detection rates of trisomy 21 among the three strategies,while the diagnostic specificity of the three strategies were more than 90％.Conclusions The three parameters are significantly increased in trisomy 21 fetus in first-trimester.First,increased NT was most commonly detected,followed by increased PT/NBL ratio,and increased FMF angle again.Detection rates for trisomy 21 fetuses in first-trimester by ultrasound screening can be significantly improved if combination of all three parameters rather than just one parameter are performed.