The validity of ultrasonographic scanning as screening method for abdominal aortic aneurysm

Abstract

Objective: the sensitivity and specificity of screening for abdominal aortic aneurysms (AAAs) with ultrasonographic scanning (US) is unknown. The aim of the study was to validate US as screening test for AAAs.

Methods and material: 4176 (76.3%) of 5470 men aged 65-73 attended hospital-based US screening for an AAA at their local hospital. Two observers and one scanner were used. The maximal anterior-posterior (AP) of the dilated aorta, or 2 cm above the bifurcation, and at the crossing of left renal vein was recorded. In 50 cases, blinded measurements were carried out by two observers. An AAA was defined as an AP diameter greater than 29 mm.

Results: the standard deviation (s.d.) of the interobserver variability of the distal AP diameter was 0.84. The mean distal AP diameter was 17. 9 mm (s.d. 2.92). Combining these data, the estimated diagnostic sensitivity was 98.9%, the estimated diagnostic specificity was 99. 9%. The interobserver s.d. of the proximal AP diameter was 1.76. The mean proximal AP diameter was 18.4 mm (s.d. 2.45). Combining these data, the estimated diagnostic sensitivity was 87.4%, the estimated diagnostic specificity was 99.9%.

Conclusion: US seems to be a valid screening method for AAA. Screening for proximal infrarenal aorta aneurysm remains acceptable because the majority of aortic diameters in this segment are so much smaller than the diameters that define an AAA.