1Department of Clinical Laboratory Medicine, University of Tsukuba, 2Cardiovascular Division, University of Tsukuba
Carotid intima-media thickness（IMT）is the imaging maker of early atherosclerosis, and has been shown to predict cardiovascular outcome in the large-scale clinical studies conducted in worldwide basis. However, there are various discrepancies in the way assessing IMT in these clinical trials- which parts are evaluated（common carotid artery, internal carotid artery, or the carotid bulb in one-side of the neck or bilaterally, in only far-wall or both near and far wall）, which way of measurements are used（single point measurement by manual caliper, or automated edge tracking measurement in certain length region）, and which types of parameters are used（mean or maximum of single measurements, mean of mean, or mean of maximum for multiple measurements）. These discrepancies limited the usage of these valuable clinical evidences to extrapolate into the individual patients. Furthermore, the lack of uniform methodology interfere the integration of IMT data in meta-analysis of IMT studies and has caused confusion about the significance of IMT in cardiovascular risk stratification. Recently published European Mannheim consensus and American society of echocardiography recommendation must be the world standard we should follow to create the better evidence. In Japan, the several original measurements of carotid IMT has been used, average of 3-points measurements in common carotid artery as "mean common carotid IMT", or sum of the maximum IMT in common, bulb, and internal carotid arteries bilaterally if the maximum IMT value are equal/greater than 1.1 mm, as "Plaque Score". These japan-original IMT parameters have grate advantage in its convenience, in which it can be used without specific computer software. And the "Plaque Score" may be good parameter to assess the severity of atherosclerotic plaque burden from the early to very advance stage of disease progress. One of the reason why these parameters are still "Japan original" and used in mainly inside Japan may be due to the lack of evidence include large number of participant around 5000. Furthermore, the incremental or superiority of the significance should be tested in compare to the world-standard measurements. In cases in we collect the data from multiple institutes, ultrasonic machine vender difference in IMT measurement still leave unsolved. Now our Japan Society of Ultrasonic in Medicine research project has just started to overcome vender difference in IMT.