DIFFERENCES IN OBSERVER VARIABILITY OF ULTRASOUND MEASUREMENTS OF THEPROXIMAL AND DISTAL ABDOMINAL-AORTA

Objective-To assess the observer variability of ultrasound measurement s of the abdominal aorta and to study whether observer variability is influenced by the site of measurement or cardiovascular risk factors. Setting-Population based screening programme for abdominal aortic aneu rysms. Methods-For 135 subjects taking part in a screening programme f or abdominal aortic aneurysms, two of the three ultrasonographers meas ured the distal and proximal ultrasound diameter of the abdominal aort a, using B-mode ultrasound, according to the Rotterdam study scanning protocol. Results-The mean difference between two different observers was 0.06 mm (95% CI -0.15 to 0.27) for measurements of the distal aort a and 0.32 mm (95% CI 0.09 to 0.55) for the proximal aorta. Maximal di fferences between observers for measurements of both the distal and pr oximal aortic diameter were 4.0 mm. Interobserver variability in the p roximal and distal measurements of the abdominal aorta was not related to the level of the major cardiovascular risk indicators. However, in terobserver variability in ultrasound measurements of the proximal aor ta increased with increasing waist circumference and increasing diamet er of the proximal aorta. Conclusion-Ultrasonographic readings of the distal and proximal aortic measurements can be interpreted within a ra nge of plus or minus 3 mm. Ultrasound measurements are more accurate f or the distal than for the proximal measurement. Definition of the aor tic diameter based on a combination of both distal and proximal measur ement may be more accurate.