The relative value of carotid noninvasive testing as determined by receiver operator characteristic curves

To determine the relative value of carotid phonoangiography (CPA), oculoplethysmography-Kartchner (OPG-K), and Doppler ultrasonic arteriography (UA), 90 vessels undergoing carotid endarterectomy were prospectively examined. By analyzing the data on receiver operator characteristic curves, the dynamic relationship between sensitivity and specificity for each of the three noninvasive tests was assessed. Disease was defined by either the percentage of angiographic stenosis or the mean pressure gradient across the carotid (deltaP). All three tests were shown to be relatively insensitive, but quite specific, if disease was defined by 50% and 60% angiographic stenosis or deltaP of greater than 10 and 20 mm Hg. By employing a more rigid definition of disease, 70% stenosis or deltaP of greater than 30 mm Hg, sensitivity was increased for all examinations and was highest in OPG-K and UA for a given specificity. The sensitivity for UA was enhanced to 80% with a comparable specificity, if those 23 UA exams with plaque were treated as positive studies. The combination of CPA, OPG-K, and UA was superior to any one of these tests alone, but the best value balancing maximum sensitivity and specificity still was associated with a 23% false negative rate. This study would suggest that these three tests should be limited to screening patients at risk for carotid stenosis and not for symptomatic patients. To achieve the best balance between sensitivity and specificity, lax threshold criteria for calling the test positive should be employed, and the tests should be used in combination.