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The Evaluation of Vertebral Fracture Assessment and Pulse Wave Velocity for the Assessment of Abdominal Aortic Calcification by Comparison to Computed Tomography

Sylvia F Edwards

Background: Abdominal aortic calcification (AAC) is a marker of subclinical atherosclerosis. Computed tomography (CT) is the gold-standard method for quantifying vascular calcification (VC) but is limited by higher radiation exposure and cost. Vertebral fracture assessment (VFA) scans have been proposed as a useful imaging tool for the semi-quantitative assessment of AAC, as images of the aorta are captured on VFA scans. Pulse wave velocity (PWV) is a simple, noninvasive method of measuring aortic stiffness - a hallmark of atherosclerosis and ageing, with a reduction in normal aortic compliance. In this study we compared VFA and PWV with CT as the gold standard of diagnosis. Lateral VFA scans may be utilised as a secondary utility to detect VC in post-menopausal women with low bone density, and associations between PWV and VC measured using lateral VFA and CT may demonstrate how measures of VC correlate with aortic stiffness. Methods and results: Four hundred and forty-four healthy post-menopausal women with a mean age of 62 (6.4 SD) years had carotid to femoral PWV measurements, and lateral VFA of the thoracic and lumbar spine, concurrently with bone densitometry measurements (DXA), to quantify AAC. A subgroup of one hundred and thirteen subjects underwent non-contrast, non-diagnostic, ungated CT scans of the chest and abdomen. Results showed AAC was present in 78% of subjects as determined by CT, and 60% with lateral VFA scans. The sensitivity of lateral VFA for detecting AAC was 55% and specificity was 48% with a PPV and NPV of 67% and 36% respectively for binary scores. Sensitivity and specificity improved when CT scores were divided into tertiles with the greatest improvement with scores ≥ 670 AU, ≥ 15304.4 AU and ≥ 0.335 cm3 for the Agatston, modified Agatston and Volume scores respectively. There were no independent associations observed between PWV and AAC measured using lateral VFA or VC measured using CT. Conclusion: Lateral VFA scans may provide a low radiation dose, and low-cost alternative to CT for evaluating higher levels of AAC and can be performed concurrently with bone densitometry assessments.