Alexandrov A V, Vital D, Brodie D S, Hamilton P, Grotta J C
Center for Noninvasive Brain Perfusion Studies, University of Texas Houston Medical School 77030, USA.
Stroke. 1997 Jun;28(6):1208-10. doi: 10.1161/01.str.28.6.1208.
Carotid ultrasound had modest accuracy in the North American Symptomatic Carotid Endarterectomy Trial (NASCET) of carotid endarterectomy in predicting severe carotid stenosis when a 250-cm/s peak systolic velocity (PSV) criterion was applied to different laboratories. We compared the performance of two independent laboratories using similar equipment (ATL-HDI Ultramark 9) but different interpretation criteria.
Consecutive patients who underwent both color-coded duplex ultrasound and intra-arterial digital subtraction angiography were studied. PSV was determined with angle correction at the site of the tightest arterial narrowing. Carotid stenosis was measured on angiograms using the North American (N) method. Sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values with 95% confidence intervals were calculated for each laboratory.
In 87 patients, 174 bifurcations were imaged. A 250-cm/s criterion was the best single predictor of a > 70% N stenosis at one laboratory (sensitivity 93% [95% confidence interval, 85 to 101], specificity 86% [76 to 96], PPV 75% [62 to 87], and NPV 96% [90 to 102]) but had modest parameters at the other laboratory (50% [34 to 64], 87%, [77 to 97], 60 [44 to 76], and 91 [82 to 100], respectively). However, the diagnostic criteria routinely used in the second laboratory included different velocity values, which when applied decreased specificity by 17% but increased sensitivity by 35% (85% [74 to 96], 70% [56 to 84], 90% [81 to 99], and 77% [64 to 90], respectively).
Despite the use of similar equipment, ultrasound grading of carotid stenosis is operator dependent and relies on different and individually validated criteria. Greater sensitivity of ultrasound screening is achieved by applying diagnostic criteria specific to each laboratory. Multicenter studies should use laboratory-specific criteria and a local validation process.
在北美症状性颈动脉内膜切除术试验（NASCET）中，当将250cm/s的收缩期峰值流速（PSV）标准应用于不同实验室时，颈动脉超声在预测严重颈动脉狭窄方面的准确性一般。我们比较了两个使用类似设备（ATL-HDI Ultramark 9）但采用不同解读标准的独立实验室的表现。
对连续接受彩色编码双功超声和动脉内数字减影血管造影的患者进行研究。在动脉最狭窄部位进行角度校正后测定PSV。使用北美（N）法在血管造影上测量颈动脉狭窄程度。计算每个实验室的敏感度、特异度以及阳性（PPV）和阴性（NPV）预测值及其95%置信区间。
在87例患者中，对174个分叉部位进行了成像。在一个实验室，250cm/s的标准是预测N狭窄程度>70%的最佳单一指标（敏感度93%[95%置信区间，85至101]，特异度86%[76至96]，PPV 75%[62至87]，NPV 96%[90至102]），但在另一个实验室其各项参数表现一般（分别为50%[34至64]，87%[77至97]，60[44至76]，91[82至100]）。然而，第二个实验室常规使用的诊断标准包含不同的流速值，应用这些值后特异度降低了17%，但敏感度提高了35%（分别为85%[74至96]，70%[56至84]，90%[81至99]，77%[64至90]）。
尽管使用了类似设备，但颈动脉狭窄的超声分级依赖于操作者，且依赖于不同的、经过个体验证的标准。通过应用每个实验室特定的诊断标准可提高超声筛查的敏感度。多中心研究应使用实验室特定的标准和当地的验证程序。
