Abstract
A routine laboratory accuracy study for identifying an internal carotid artery (ICA) diameter stenosis of 70% using an ICA/CCA ratio of 4.0 revealed an overall accuracy of 85% but the positive predictive value (PPV) was noted to be only 56%. A subsequent Receiver Operating Characteristics (ROC) curve analysis compared carotid duplex measurements to arteriography in 239 carotid arteries. The analysis yielded new thresholds for single velocity and B-mode image measurements as follows: peak systolic velocity (PSV) 267 cm/sec, end diastolic velocity (edv) 99 cm/ sec, ICA/CCA ratio 4.2, and an image diameter measurement of 78%. The overall accuracy for each parameter was 91, 83, 90, and 89% respectively with PPV's of 65, 66, 66, and 74% each. Further analysis combining these best thresholds in all possible combinations revealed overall accuracies that ranged between 85–94%. The three best combinations with the highest overall accuracies were a) image diameter measurement >78% with ICA/CCA ratio >4.2 (94%), b) ratio >4.2 with PSV >267 cm/ sec (91%) and c) image diameter >78% with PSV >267 cm/sec (91%). The PPV's for these combinations were 86%, 80%, and 70% respectively.
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