Department of Obstetrics and Gynecology, University of São Paulo, São Paulo, Brazil.
J Ultrasound Med. 2010 Dec;29(12):1741-7. doi: 10.7863/jum.2010.29.12.1741.
The purpose of this study was to estimate the Down syndrome detection and false-positive rates for second-trimester sonographic prenasal thickness (PT) measurement alone and in combination with other markers.
Multivariate log Gaussian modeling was performed using numerical integration. Parameters for the PT distribution, in multiples of the normal gestation-specific median (MoM), were derived from 105 Down syndrome and 1385 unaffected pregnancies scanned at 14 to 27 weeks. The data included a new series of 25 cases and 535 controls combined with 4 previously published series. The means were estimated by the median and the SDs by the 10th to 90th range divided by 2.563. Parameters for other markers were obtained from the literature.
A log Gaussian model fitted the distribution of PT values well in Down syndrome and unaffected pregnancies. The distribution parameters were as follows: Down syndrome, mean, 1.334 MoM; log(10) SD, 0.0772; unaffected pregnancies, 0.995 and 0.0752, respectively. The model-predicted detection rates for 1%, 3%, and 5% false-positive rates for PT alone were 35%, 51%, and 60%, respectively. The addition of PT to a 4-serum marker protocol increased detection by 14% to 18% compared with serum alone. The simultaneous sonographic measurement of PT and nasal bone length increased detection by 19% to 26%, and with a third sonographic marker, nuchal skin fold, performance was comparable with first-trimester protocols.
Second-trimester screening with sonographic PT and serum markers is predicted to have a high detection rate, and further sonographic markers could perform comparably with first-trimester screening protocols.
本研究旨在评估超声鼻前厚度（PT）单独测量以及与其他标记物联合测量在二 孕期唐氏综合征（DS）的检出率和假阳性率。
采用数值积分法进行多变量对数高斯建模。PT 分布参数，以正常妊娠特异性中位数（MoM）的倍数表示，来源于 14-27 孕周 105 例 DS 妊娠和 1385 例正常妊娠的超声检查数据。该数据包括与之前发表的 4 个系列数据合并的 25 例新病例和 535 例对照病例。通过中位数估计均值，通过第 10 到 90 百分位数范围除以 2.563 估计标准差。其他标记物的参数则来源于文献。
对数高斯模型很好地拟合了 DS 和正常妊娠的 PT 值分布。分布参数如下：DS 妊娠，均值 1.334 MoM；log（10）SD，0.0772；正常妊娠，分别为 0.995 和 0.0752。对于 1%、3%和 5%假阳性率，PT 单独预测的检出率分别为 35%、51%和 60%。将 PT 添加到 4 项血清标志物方案中，与血清标志物相比，检出率提高了 14%至 18%。同时测量 PT 和鼻骨长度，检出率提高了 19%至 26%，再增加第三个超声标记物，颈项透明层（nuchal skin fold，NSF），其表现与早孕期方案相当。
超声 PT 和血清标志物的二 孕期筛查具有较高的检出率，而进一步的超声标记物可能与早孕期筛查方案具有可比性。
