Ankle-brachial index as a prognostic factor and screening tool in coronary artery disease: does it work?

ABSTRACT

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. 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. 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]. 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