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The reproducibility of measuring maximum abdominal aortic aneurysm diameter from ultrasound imaging
The reproducibility of measuring maximum abdominal aortic aneurysm diameter from ultrasound imaging
REVIEWED BY | Daniel Rae ASA SIG: Vascular
REFERENCE | Authors: Matthews EO, Pinchbeck J, Elmore K, Jones RE, Moxon JV and Golledge J. Journal: The Ultrasound Journal
WHY THE STUDY WAS PERFORMED
The most important established predictor of abdominal aortic aneurysm (AAA) growth and rupture is the maximum AAA diameter. This is used in clinical practice to guide patient management and surgical decision making.
Reproducible methods to measure AAA diameter are therefore both important clinically and in research. Disparate methods of calliper placement have been reported to cause differences of up to 5 mm.
HOW THE STUDY WAS PERFORMED
A sample of 50 participants was selected with infrarenal aneurysms measuring between 30–55 mm in maximum diameter. Three observers were present: a qualified vascular sonographer, a clinical medical student, and a research worker. Five total measurements were taken of the aortic aneurysm:
• three were in the anterior-posterior plane – outer-to-outer (OTO), inner-to-inner (ITI) and leading edge-to-leading edge (LETLE)
• two were in the transverse plane – outer-to-outer and inner-to-inner.
Figure 1 shows ideal placement of callipers for ITI ( / ), LETLE ( ), OTO ( / ) in both anterior-posterior and transverse direction. OTO: outer-to-outer; LETE: leading edge-to-leading edge; ITI: inner-to-inner
The test was then repeated later with observers blinded to their previous results.
Figure 1: Illustration of a transverse view of an abdominal aortic aneurysm with the participant in the supine position.
WHAT THE STUDY FOUND
The data suggests that the calliper position in the anterior-posterior (AP) plane, with measurements obtained perpendicular to the orientation of the ultrasound probe, showed no statistical difference between ITI, OTO and LETE placement. These findings indicate that measurements in the AP plane should be used in clinical practice and clinical trials. The measurement of transverse ITI or OTO diameter is not as reproducible.
Reproducibility was demonstrated to be better within rather than between operators, suggesting repeat measurements should be taken by the same observer.
RELEVANCE TO CLINICAL PRACTICE
The results from this study highlight the importance of taking AAA measurements in an AP plane rather than in a transverse plane for diagnostic accuracy and reproducibility. It also raises the suggestion of having the same operator perform surveillance studies due to increased accuracy of intraoperator observations.
