Ankle-Brachial Index as a Prognostic Factor and Screening Tool in Coronary Artery Disease: Does it Work?

Background: Given the lack of consistency in the literature regarding the reliability of the ankle-brachial index (ABI) as a valid screening tool and an independent risk indicator of cardiovascular events and mortality, we compared it with angiography as a reference standard test. Methods: This case-control study, conducted between 2010 and 2011 in Tehran Heart Center, recruited 362 angiographically confirmed cases of coronary artery disease (CAD) and 337 controls. A standard protocol was used to measure the ABI and different CAD risk factors. Results: A low ABI had specificity of 99.7%, positive predictive value of 95.8%, negative predictive value of 49.8%, sensitivity of 64%, likelihood ratio of 24.07, and odds ratio (OR) of 22.79 (95%CI: 3.06-69.76). The role of the associated risk factors was evaluated with OR (95%CI), with the variables including gender 3.15 (2.30-4.30), cigarette smoking 2.72 (1.86-3.99), family history 1.72 (1.17-2.51), diabetes 1.66 (1.15-2.4), and dyslipidemia 1.38 (1.02-1.88). In a multivariate model, the following variables remained statistically significantly correlated with CAD [OR (95%CI)]: ABI 13.86 (1.78-17.62); gender 3.69 (2.43- 5.58); family history of CAD 2.18 (1.41-3.37); smoking 1.69 (1.08-2.64); age 1.04 (1.02-1.06). Conclusions: A low ABI had specificity of 99.7%; however, because of its low sensitivity (64%), we should consider CAD risk factors associated with a low ABI in order to use it as a first-line screening test.