EQUIVALENCE OF MEASUREMENTS OF CAROTID STENOSIS - A COMPARISON OF 3 METHODS ON 1001 ANGIOGRAMS

Background and Purpose There is confusion about how carotid stenosis s hould be measured on angiograms. If the results of research based on d ifferent methods of measurement of stenosis are to be discussed and th e results of clinical trials properly applied to routine clinical prac tice, measurements made by the different methods must be formally comp ared. Methods The method of measurement of stenosis used in the Europe an Carotid Surgery Trial (ECST), that used in the North American Sympt omatic Carotid Endarterectomy Trial (NASCET), and a method based on me asurement of the common carotid (CC) artery lumen diameter were compar ed. Carotid stenosis was measured by two observers, working independen tly and using the three different methods of measurement, on the angio graphic view of the symptomatic carotid stenosis that showed the most severe disease in 1001 patients from the ECST. Results The results of using the ECST and CC methods differed from those of using the NASCET method in the classification of stenoses as mild (0% to 29%), moderate (30% to 69%), or severe (70% to 99%) in 51% of measurements. The ECST and CC methods indicated that twice as many stenoses were severe as d id the NASCET method, and classified less than a third of the number o f stenoses as mild. The results of the ECST and CC methods differed fr om each other in 15% of measurements. The relations between measuremen ts made by each method to those made by the others were approximately linear, so a simple equation could be derived to convert measurements made by one method to measurements made by the others. Conclusions The re were major and clinically important disparities between measurement s of stenosis made using different methods of measurement on the same angiograms. However, it is possible to convert measurements made by on e method to those of another using a simple arithmetic equation.