LAUSR

Objective: The current “gold standard” for diagnosis of peripheral artery disease (PAD) is ankle-brachial pressure index (ABI). PAD diagnosis is complicated by vascular calcification, which causes stiff vessels and may falsely elevate ABI. Few studies have used peripheral calcium score (PCS) in lower extremity arteries to measure PAD burden, and no studies have compared the diagnostic value of PCS with ABI. The primary aim of this study was to describe the association of PCS with continuous ABI measurements and categories of ABI in a retrospective cohort design. Methods: We identified 50 patients with PAD who underwent both computed tomography angiography and ABI measurements. ABI measurements were divided into categories based on PAD severity: severe (<0.5), moderate (0.5-0.9), normal (0.9-1.4), and noncompressible (>1.4). We evaluated runoff computed tomography angiograms that imaged from the abdominal aorta through the distal lower extremities and determined total calcium volume of plaques with density >130 HU and area >1 mm from the infrarenal abdominal aorta to the foot using TeraRecon (Foster City, Calif) software by two independent readers (intraclass correlation 99%). We explored the relationship between ABI and PCS using multiple linear regression and analysis of covariance while adjusting for age, race, smoking status, hypertension, hyperlipidemia, type 2 diabetes, and chronic kidney disease. Results: We found that ABI was inversely associated with PCS in linear regression (P < .01; Fig 1). Differences in mean PCS were also statistically significant across ABI categories (F(3,29) 1⁄4 5.03; P 1⁄4 .01; Fig 2). The mean PCS was 11,269.5 mm (standard deviation [SD], 10,519.4 mm) in patients with ABI <0.5, 4360.8 mm (SD, 3845.8 mm) in ABI 0.5 to 0.9, 3213.8 mm (SD, 4187.5 mm) in ABI 0.9 to 1.4, and 2452.3 mm (SD, 1070.3 mm) in ABI>1.4. Across subgroups, the mean PCS was significantly different for ABIs <0.5 and 0.5 to 0.9 (P 1⁄4 .02), <0.5 and >1.4 (P < .001), 0.5 to 0.9 and >1.4 (P 1⁄4 .04), and 0.9 to 1.4 and >1.4 (P 1⁄4 .05). Interestingly, the percentage of tibial calcium score relative to overall PCS was much lower in severe PAD (ABI <0.5), 0.03%, vs noncompressible PAD (ABI >1.4), 35.7% (P 1⁄4 .02). Conclusions: ABI values were inversely associated with PCS, and mean PCS was significantly higher in severe PAD (ABI <0.5). Mean PCSmay be a valid measure of PAD severity, and percentage of tibial calcium may help quantify PAD burden in noncompressible vessels. Our study serves as proof of concept for the development of a comprehensive PCS system to diagnose and to evaluate PAD severity, particularly in high-risk subpopulations in which noninvasive studies may be unreliable.