Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Shatin, Hong Kong SAR, China.
Ultrasound Obstet Gynecol. 2010 Mar;35(3):286-91. doi: 10.1002/uog.7549.
To assess the relative performance of a multi-stage first-trimester screening protocol for fetal Down syndrome.
Data from 10,767 women who underwent combined ultrasound and biochemistry (BC) screening in the first trimester were reanalyzed using a contingent model approach. Amongst the 10,854 fetuses with known outcome, 32 had Down syndrome, 232 had other abnormalities and 10,590 were unaffected. Nuchal translucency (NT), BC and combined (NT-BC) gestational age-specific risks were calculated for each individual using The Fetal Medicine Foundation risk calculation algorithms (Mixture Model and Biochemistry). Individual patients were categorized as at low, high or intermediate risk according to one of the following three strategies. In 'Strategy-NT-BC' initial screening was performed using both NT and BC. In 'Strategy-BC' initial screening was undertaken using maternal serum markers followed by NT assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000) while in 'Strategy-NT' initial screening was undertaken using NT followed by serum marker assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000). The nasal bone was assessed in those with an intermediate risk as the final stage in each of the three strategies. Those with an adjusted risk of 1 in 100 or higher after nasal bone assessment were reclassified as high risk. Detection and false-positive rates were compared between differing strategies in our local population, and this analysis was also performed with the maternal age for our population standardized to the distribution found in England and Wales.
In our local population the detection rate for a 5% false-positive rate using a combined screening policy (NT-BC) was 88% (95% CI, 75.3-98.9%), and 2.3% had an absent nasal bone. The respective detection rate and false-positive rate of the three multi-stage screening strategies were: Strategy-NT-BC: 87.5 and 2.5%; Strategy-BC: 87.5 and 5%; Strategy-NT: 84.4 and 2.9%. In the contingent Strategy-BC only 29% of those initially screened using serum markers required an NT scan. If the model were applied to a hypothetical obstetric population standardized to the maternal age distribution in England and Wales, the detection and false-positive rates of the same three screening strategies would be: Strategy-NT-BC: 86.2 and 1.9%; Strategy-BC: 82.8 and 4%; Strategy-NT: 75.8 and 2.3%, respectively.
First-trimester contingent screening provides detection and false-positive rates comparable to those achieved using combined screening, but could be used to significantly reduce the number of scans performed.
评估多阶段早孕期唐氏综合征筛查方案的相对性能。
使用条件模型方法重新分析了 10767 名接受早孕期联合超声和生物化学（BC）筛查的妇女的数据。在已知结局的 10854 例胎儿中，32 例患有唐氏综合征，232 例患有其他异常，10590 例未受影响。使用胎儿医学基金会风险计算算法（混合模型和生物化学）为每个个体计算特定于妊娠周龄的颈后透明带（NT）、BC 和联合（NT-BC）风险。根据以下三种策略之一，将个体患者归类为低、高或中风险。在“策略-NT-BC”中，使用 NT 和 BC 进行初始筛查。在“策略-BC”中，使用母体血清标志物进行初始筛查，然后对风险为 1:51<风险≤1:1000 的个体进行 NT 评估，而在“策略-NT”中，使用 NT 进行初始筛查，然后对风险为 1:51<风险≤1:1000 的个体进行血清标志物评估。在三种策略中的每一种中，对于风险为 1:51<风险≤1:1000 的个体，在最后阶段评估鼻骨。经鼻骨评估后，调整后的风险为 1/100 或更高的个体被重新归类为高风险。在我们的本地人群中，比较了不同策略之间的检测率和假阳性率，并使用我们人群的母体年龄标准化为英格兰和威尔士的分布，对该分析进行了进一步分析。
在我们的本地人群中，使用联合筛查策略（NT-BC）时，假阳性率为 5%的检测率为 88%（95%CI，75.3-98.9%），并且有 2.3%的个体没有鼻骨。三种多阶段筛查策略的检测率和假阳性率分别为：策略-NT-BC：87.5%和 2.5%；策略-BC：87.5%和 5%；策略-NT：84.4%和 2.9%。在条件策略-BC 中，最初使用血清标志物筛查的个体中，只有 29%需要进行 NT 扫描。如果将该模型应用于假设的产科人群，并根据英格兰和威尔士的母体年龄分布进行标准化，那么相同的三种筛查策略的检测率和假阳性率将为：策略-NT-BC：86.2%和 1.9%；策略-BC：82.8%和 4%；策略-NT：75.8%和 2.3%。
早孕期条件筛查提供的检测率和假阳性率与联合筛查相当，但可用于显著减少进行的扫描数量。
