胎儿颈项透明层产前超声诊断及质量控制

Prenatal ultrasound diagnosis and quality control of fetal nuchal translucency

目的:在临床超声检查中很难对每例胎儿颈项透明层(nuchal translucency,NT)和头臀径(crown-rump length,CRL)的图像进行质量控制(以下简称“质控”),但测量的微小差异可能增加假阳性或假阴性诊断的概率,因此,有必要建立胎儿NT检查的质控体系。本研究旨在通过对胎儿NT与CRL测量进行质控,评估超声医师在妊娠早期NT测量中的准确性,并分析增加胎儿结构平面筛查对于染色体异常检出率的影响。方法:收集胎儿NT检查质控前和质控后各12个月的病例数据,质控前和质控后病例分别为2 214例及2 538例,分析病例NT中位数的倍数(NT multiple of median,NT-MoM)、log10MoM的标准差[standard deviation (SD) of log10MoM,(SD) log10MoM]、NT基于CRL的回归斜率(the slope of NT on CRL,SNC)3种质控数据。通过个体CRL的NT-MoM在正常中位数曲线0.9~1.1MoM范围内的程度来监测NT测量的性能,同时对log10MoM的SD和SNC进行评价。根据超声医师不同工作年限进行分组(<3年组,3~6年组,>6年组),比较各组间的NT-MoM值,并对质控期内病例NT增厚、结构畸形、染色体异常的数据进行回顾性分析。结果:根据美国NTQR项目组的曲线方程,质控前NT-MoM值为0.921 7 MoM,(SD)log10MoM值为0.091 92,SNC值为12.20%;质控后NT-MoM值为0.948 3 MoM,(SD) log10MoM值为0.094 81,SNC值为11.43%;质控前后NT-MoM值比较,差异有统计学意义(P<0.000 1)。质控前及质控后不同工作年限超声医师测量的NT-MoM值比较,差异均有统计学意义(均P<0.000 1);工作年限3~6年组以及>6年组质控后的NT-MoM值均高于质控前(均P<0.05),<3年组质控前和质控后比较,差异无统计学意义(P>0.05)。在质控后,胎儿NT增厚不伴明显结构异常占19.05%;NT增厚伴结构异常占47.62%;NT正常但结构异常占33.33%。胎儿合并心脏畸形36例,占总异常率的20.34%,染色体检测阳性率为36%。结论:质控后,超声医师对NT的测量会更精确,但测量者之间仍然存在差异;经验丰富的超声医师的测量值更接近预期值,通常小于预期值。对胎儿NT和CRL测量值进行监测,有助于提高测量准确度;增加NT检查的结构筛查,特别是对于胎儿心脏的筛查,有利于提高染色体的异常检出率。

Objective:In clinical ultrasound examinations,it is challenging to perform quality control on the images of each fetal nuchal translucency(NT)and crown-rump length(CRL).However,small measurement differences can increase the probability of false-positive or false-negative diagnosis.Therefore,it is necessary to establish a quality control system for fetal NT examination.This study aims to control the quality of fetal NT and CRL measurements,evaluate the accuracy of ultrasound physicians in early pregnancy NT measurements,and analyze the impact of increased fetal structure screening on the detection rate of chromosomal abnormalities.Methods:Data were collected from cases before and after 12 months of NT examination quality control,with 2214 before quality control and 2538 cases after quality control.Three quality control data metrics were analyzed:NT multiple of median(NT-MoM),standard deviation(SD)of log10MoM[(SD)log10MoM],and the slope of NT on CRL(SNC).The performance of NT measurements was monitored through the individual CRL NT-MoM within the 0.9-1.1 MoM range of the normal median curve,while grouped based on different years of experience(<3 years,3-6 years,>6 years),and NT-MoM values among these groups were compared.Data on NT thickening,structural anomalies,and chromosomal abnormalities were retrospectively analyzed during the quality control period.Results:According to the curve equation of the American NTQR project group,the NT-MoM value before quality control was 0.9217 MoM,the(SD)log10MoM value was 0.09192,and the SNC value was 12.20%.After quality control,the NT-MoM value was 0.9483 MoM,the(SD)log10MoM value was 0.09481,and the SNC value was 11.43%.The comparison of NT-MoM values before and after quality control showed a statistically significant difference(P<0.0001).The comparison of NT-MoM values measured by ultrasound physicians with different years of experience before and after quality control also showed statistically significant differences(P<0.0001).The NT-MoM values for the 3-6 years and>6 years groups were higher after quality control(P<0.05),while the<3 years group showed no significant difference before and after quality control(P>0.05).After quality control,cases of NT thickening without significant structural abnormalities accounted for 19.05%,NT thickening with structural abnormalities accounted for 47.62%,and NT normal with structural abnormalities accounted for 33.33%.There were 36 cases of fetal heart abnormalities,accounting for 20.34%of the total abnormality rate,with a positive rate of 36%in chromosome tests.Conclusion:After quality control,ultrasound physicians measure NT more accurately,but differences among measurements remain.Measurements by experienced ultrasound physicians are closer to expected values,usually lower than expected.Monitoring fetal NT and CRL measurements helps improve measurement accuracy.Increasing structural screening during NT examinations,especially for the fetal heart,enhances the detection rate of chromosomal abnormalities.