| 摘要: |
| 目的：探讨使用不同颈项透明层厚度中位数对唐氏筛查效能的影响。
方法：随机选择 2013年4月至2016年12月广州医科大学附属第三医院产前诊断科进行B超NT检查的23446例单胎妊娠的孕妇，其中包含57例21三体和61例其他染色体异常胎和23328例表型正常或核型正常的胎儿。这些检查全部由11位获得NT检查资格的超声医师完成。以英国胎儿医学基金会（Fetal Medical Foundation，FMF）推荐NT预期中位数对NT测量值转换为NT中位数的倍数(multiply of median, MoM)，统计分析11位超声操作者的NT-MoM中位数，按操作者个人NT-MoM中位数所属区间（<0.9，0.9~1.1,>1.1）不同将NT值分三组。然后再分别用本地中心特有的和NT测量操作人员个体化的中位数将NT值转换为NT-MoM，分析三组NT-MoM值数据分布的变化，评估三组NT唐氏筛查效能的改变。并运用指数加权移动平均线(EWMA)质控图分析三组NT测量操作人员的失控NT点比率。
结果：FMF预期中位数计算的NT-MoM中位数小于0.9的超声操作人员有2位，中位数在0.9~1.1之间的有6位，中位数大于1.1的有3位。NT-MoM中位数小于0.9或大于1.1的5位超声操作者的NT测量值在使用本地中心特有的中位数转换为NT-MoM后，其中位数仍然小于0.9或大于1.1，所在区间属性不变，而在使用操作人员个体化中位数后其NT-MoM中位数回归0.9~1.1区间。cutoff=1:250时使用三种NT中位数的21三体检出率比较无显著差别，但假阳性率的差异具有统计学意义（P<0.05），操作人员个体化的假阳性率均比其它两者低。多元逻辑回归分析显示使用FMF中位数的假阳性率与超声操作者的NT-MoM中位数和EWMA失控百分率有关，似然比分别为408.8（95%CI 260184.6~0.64，P<0.05）和1.29（95%CI 0.44~3.81，P<0.05）。另外，操作人员个体化中位数转换的NT测定值EWMA失控率均比其他两组低。
结论：使用NT扫描操作者的个人中位数可一定程度上降低NT测量结果的变异性，从而改善NT唐氏筛查的效能，保持适当的NT筛查效能需要持续监测超声操作者的检测质量。 |
| 关键词: 颈部透明带检查 敏感性与特异性 质量控制 唐氏综合征 妊娠初期 |
| DOI： |
| 投稿时间：2019-02-20修订日期：2019-03-10 |
| 基金项目: |
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| The effect of using different NT expected medians on first trimester down screening performance |
| Qiuwenjun,Liuzhongming |
| (the Third Affiliated Hospital of Guangzhou Medical University;The First Affiliated Hospital of Guangzhou Medical University) |
| Abstract: |
| Objective: to investigate the effect of using different NT expected medians on down screening performance
Method: 23446 cases of singleton pregnancies were unselected for nuchal translucency scans in first trimester in the prenatal diagnose center of the third hospital affiliated Gang Zhou medical university between April 2013 and December 2016, of whom there were 57 twenty on trisomies and 61 other chromosomal abnormalities and 23328 fetuses with normal phenotype or karyotypes. All of those NT examinations were performed by 11 credentialed sonographers.NT measurements were transformed into NT-MoM (multiply of median) by the expected medians from the recommendation of FMF (Fetal Medicine Foundation). Based on the statistic analysis of the medians of NT-MoM from those 11 sonographers, according to the different individual interval NT-MoM were grouped three categories(<0.9，0.9~1.1,>1.1) . Then, local center-specific or practitioner-specific medians were used to convert NT measurements into NT-MoM. The changes of NT-MoM distributions from the three different categories were analyzed and the accessment of their performance of NT screening for Down syndrome were also conducted. Further more, out of control points percentages of ultrasound practitioner were analyzed with EWMA (exponentially weighted moving average) chart for nuchal translucency quality.
Result: There were two ultrasound practitioners whose medians of NT-MoM calculated with expected NT medians from FMF recommendation were less than 0.9, six practitioners between 0.9 and 1.1, three practitioners more than 1.1. NT-MoM medians of the five ultrasound practitioners below 0.9 or above 1.1 were still below 0.9 or above 1.1 after using local center-specific expected NT medians, which category interval did not change, whereas their NT-MoM medians transformed with practitioner-specific NT medians returned into 0.9~1.1 range. Application of the three different NT medians resulted in no significant differences of 1:250 cutoff detection rate of down screening, but the false positive rate of 1:250 cutoff from the practitioner specific medians was lower than from the others. There was association between false positive rate and practitioner NT-MoM medians and the percentage of out control points on EWMA chart with multivariable logistic regression, which OR were 408.8（95%CI 260184.6~0.64，P<0.05）and 1.38（95%CI 1.13~1.69，P<0.05）respectively. In addition, the practitioner-specific group had lower percentage of out control points than others groups.
Conclusion: Utilization of practitioner-specific NT expected medians reduces variation of NT measurement value to a certain extent to improve the performance of NT down screening. Continuous monitoring of sonographic practitioner NT measurement quality is needed to maintain proper NT down screening. |
| Key words: Nuchal translucency measurement sensitivity and specificity quality control Down syndrome pregnancy trimester, first |
