Inter/intra-observer variability of carotid and femoral bifurcation intima-media thickness measurements

Abstract

Arterial wall thickening may be quantitatively assessed by measuring the intima-media thickness (IMT) with high resolution ultrasound. Previous studies have shown a good inter/intraobserver variability of IMT measurements in the common carotid. In this study we evaluated the inter/intraobserver variability of IMT measurements in 10 randomly selected asymptomatic subjects (age 55.4 +/- 6). Two carotids and two femorals were studied in each subject. IMT for each patient was the average of five IMT measurements at the artery bifurcation. Three observers repeated the scanning and the measurements twice with no knowledge of the previous readings. The between observer coefficient of variation (CV) was 8.45%; the intraobserver CV (mean of carotids and femorals) varied from 4.4 to 5.1% for the three observers who measured IMT three times. The mean absolute difference between the first and the third measurement was 0.0738 mm. In conclusion IMT measurement variability is mostly due to differences between observers. The intraobserver variability is very small. IMT measurements at the carotid and femoral bifurcations have a low variability and are a good expression of atherosclerosis as they consider early lesions at the bifurcation level which may not be observed in the common carotid.