Baseline reproducibility of B-mode ultrasonic measurement of carotid artery intima-media thickness: the European Lacidipine Study on Atherosclerosis (ELSA)

Background and objective The European Lacidipine Study of Atherosclerosis ( ELSA) is a prospective, randomized, double-blind, multi-national interventi onal trial to determine the effect of four-year treatment using the calcium antagonist lacidipine versus the beta-blocker atenolol on the progression of carotid atherosclerosis in 2259 asymptomatic hypertensive patients. B-mo de ultrasound is used to measure the primary and secondary endpoints includ ing the mean maximum intima-media thickness (IMT) of the carotid bifurcatio ns and the common carotid arteries (CBMmax), the mean maximum IMT of 12 sta ndard carotid sites (M-max) and the overall maximum IMT (T-max). This paper reports the cross-sectional reproducibility of ultrasound measurements at baseline. Method To evaluate measurement reliability, each patient is scanned twice a t baseline and again at four annual visits, with 80% of the replicate scans performed by the same sonographer and 20% by a different sonographer; 50% of the replicate scans are read by the same reader and the other 50% by dif ferent readers. Results The overall coefficient of reliability (R) was 0.859 for CBMmax, 0. 872 for M-max and 0.794 for T-max. The reliability for CBMmax was stable du ring the 1 3/4-year baseline period (R = 0.848 to 0.953) and was uniform am ong the 23 field centres (R = 0.798 to 0.926). Intra- and inter-reader reli ability were 0.915 and 0.872 respectively, and intra-sonographer reliabilit y was 0.866. Conclusion The results demonstrate that by implementing standardized protoc ols and strict quality control procedures, highly reliable ultrasonic measu rements of carotid artery IMT can be achieved in large multi-national trial s. J Hypertens 2000, 18:197-201 (C) Lippincott Williams & Wilkins.