Elgersma O E, van Leersum M, Buijs P C, van Leeuwen M S, van de Schouw Y T, Eikelboom B C, van der Graaf Y
Department of Radiology, the Department of Vascular Surgery, and the Julius Center for Patient Oriented Research University Hospital Utrecht, The Netherlands.
Stroke. 1998 Nov;29(11):2352-6. doi: 10.1161/01.str.29.11.2352.
Two surgical trials established that carotid endarterectomy is beneficial to symptomatic patients who have a severe internal carotid artery (ICA) stenosis on angiograms. Duplex ultrasonography-derived hemodynamic parameters show a good correlation with angiography and are often used for detecting severe ICA stenoses. However, duplex performance is ultrasound machine and operator dependent. Over time both may change, possibly affecting duplex performance. We compared duplex performance of 2 time periods in 1 specific vascular laboratory using angiography as the gold standard.
Consecutive patients who underwent both angiography and duplex examinations of the ICA were evaluated (first period, 60 patients; second period, 61 patients). Peak systolic velocity and several other hemodynamic parameters and ratios were analyzed by receiver operating characteristic curves in their ability to detect severe ICA stenoses. The optimal parameter and threshold were determined for each period. Subsequently, duplex test characteristics were compared after the optimal thresholds of both the first and the second periods were applied in the second period.
In both periods peak systolic velocity of the ICA was the best test parameter; areas under the receiver operating characteristic curve were similar (0.957 and 0.954, respectively). However, the optimal threshold was different. The optimal threshold in the second period was 270 cm/s. When the optimal threshold of 210 cm/s of the first period was applied in the second period, test characteristics changed significantly. Sensitivity increased from 98% to 100%, and specificity decreased from 85% to 71% (P=0.004).
The optimal threshold for detecting severe ICA stenoses with duplex ultrasonography in our laboratory changed over time. Individual laboratories should assess duplex accuracy regularly and adjust adopted criteria if necessary to keep diagnostic performance optimal.
两项外科手术试验证实，颈动脉内膜切除术对血管造影显示有严重颈内动脉（ICA）狭窄的有症状患者有益。双功超声检查得出的血流动力学参数与血管造影显示出良好的相关性，并且常被用于检测严重的ICA狭窄。然而，双功超声的性能取决于超声机器和操作人员。随着时间推移，两者都可能发生变化，这可能会影响双功超声的性能。我们以血管造影作为金标准，比较了在一个特定血管实验室中两个时间段的双功超声性能。
对连续接受ICA血管造影和双功超声检查的患者进行评估（第一时间段，60例患者；第二时间段，61例患者）。通过接受者操作特征曲线分析收缩期峰值流速以及其他几个血流动力学参数和比率检测严重ICA狭窄的能力。确定每个时间段的最佳参数和阈值。随后，在第二时间段应用第一和第二时间段的最佳阈值后，比较双功超声检查特征。
在两个时间段中，ICA的收缩期峰值流速都是最佳检测参数；接受者操作特征曲线下的面积相似（分别为0.957和0.954）。然而，最佳阈值不同。第二时间段的最佳阈值为270 cm/s。当在第二时间段应用第一时间段210 cm/s的最佳阈值时，检查特征发生了显著变化。敏感性从98%增加到100%，特异性从85%降至71%（P = 0.004）。
在我们的实验室中，用双功超声检测严重ICA狭窄的最佳阈值随时间发生了变化。各个实验室应定期评估双功超声的准确性，并在必要时调整采用的标准，以保持最佳诊断性能。
