Comparison of three ultrasound methods of measuring the diameter of the abdominal aorta.

Abstract

Three ultrasound methods of measuring the diameter of the abdominal aorta exist: the outer-to-outer (OTO) method, where callipers are placed on the outer layer of the aortic wall; the inner-to-inner (ITI) method, where callipers are placed on the inner layer of the aortic wall; and the leading edge-to-leading edge (LELE) method, where callipers are placed on the outer layer of the anterior wall and the inner layer of the posterior wall. The aim was to determine the variability of the three methods, differences between them, and the consequences on prevalence estimates. Some 127 consecutive patients with a small abdominal aortic aneurysm (AAA) were included. The maximal anteroposterior diameter was measured using the OTO, ITI and LELE methods by two vascular sonographers who were blinded to each other's measurements. The variability was described as the standard deviation. The variability was 2.7 (95 per cent limits of agreements ± 5.4) mm for the OTO, 2.3 (± 4.6) mm for the ITI and 2.0 (± 4.0) mm for the LELE method. The corresponding coefficients of variability were 6.4, 6.1 and 5.0 per cent. The difference was 4.1 mm between ITI and OTO (P < 0.001), 2.0 mm between ITI and LELE (P < 0.001), and 2.1 mm between LELE and OTO (P < 0.001). LELE measurement was the most reproducible method of measuring the abdominal aorta. All methods showed a high degree of variability.