Use of inner versus outer wall for assessing abdominal aortic aneurysm size

Abstract

We read the article by Thapar et al. with interest and have a number of concerns regarding the methodology used in their study. From the article, it is not clear whether the clinical vascular scientists who took part were formally trained in the two methods of aorta/aneurysm diameter measurements. If the vascular scientists had a preference for one method of measurement in their routine practice, then this would bias the outcome of their measurements. Sonographers in the NHS Abdominal Aortic Aneurysm Screening Programme (AAASP) undergo formal training and the issue of placement of measurement calipers (particularly in identifying thrombus where confusion can arise) is carefully addressed. Therefore, it would be more valid if the sonographers in this study had been compared with those fully accredited by the NHSAAASP. We also have concern about the capture of the image used in Figure 2, given by the authors as an example of ultrasound diameter measurement. This image would fail the quality assurance requirements of the NHSAAASP with particular respect to the excessively high gain used at the posterior wall of the aneurysm. This makes it almost impossible to identify either the outer or inner wall. There is currently much debate on which method of AAA measurement is more reliable. We feel that effort should be made to ensure that correct methodology is used before discrediting one or the other method.