DUPLEX ULTRASOUND CRITERIA FOR THE IDENTIFICATION OF CAROTID STENOSISSHOULD BE LABORATORY SPECIFIC

Background and Purpose Published criteria for the determination of car otid stenosis have been widely applied by vascular laboratories. We co mpared two vascular laboratories and their duplex ultrasound (DU) mach ines in terms of their overall diagnostic performance and the optimal criteria to identify patients who have a 70% to 99% stenosis of the in ternal carotid artery. Methods Measurements of stenosis by DU and angi ography were compared for 123 carotid arteries (60 arteries, laborator y A; 63 arteries, laboratory B). Receiver operating characteristic (RO C) curves were created, and the areas under the ROC curves and the opt imal criteria for determining a 70% to 99% stenosis were compared. Mul tiple regression analysis was used to measure the effect of laboratory on the relationship between angiographic stenosis and DU velocity par ameters. Results Areas under the ROC curves were similar for both labo ratories (0.89 to 0.90, laboratory A; 0.90 to 0.92, laboratory B). How ever, the optimal criterion for the identification of a 70% to 99% car otid stenosis was different for each laboratory. For most velocity par ameters, based on regression analyses, the predicted percent angiograp hic stenosis for laboratory A was significantly greater than that for laboratory B. In addition, performance differed between the laboratori es when established criteria from the literature were applied. Conclus ions Two vascular laboratories with similar diagnostic accuracy by ROC analysis have markedly different ''optimal'' DU criteria. For a given angiographic stenosis, velocities in one laboratory were consistently greater than those in the other laboratory. Laboratory-specific crite ria rather than published criteria should be used to identify patients with internal carotid artery stenoses.