Duplex ultrasound of the superficial femoral artery is a better screening tool than ankle-brachial index to identify at risk patients with lower extremity atherosclerosis

Abstract

Objectives: The purpose of vascular disease screening is early identification of atherosclerotic disease and the aim of an ankle-brachial index (ABI) is to identify lower extremity (LE) atherosclerosis as a marker for coronary artery disease (CAD). However, early evidence of atherosclerosis may be present in the superficial femoral artery (SFA) with a normal resting ABI. This study was performed to determine if SFA duplex ultrasound (DUS) could detect more patients with LE atherosclerosis than an ABI; be performed in the same or less time as the ABI measurement; and be associated with similar vascular disease markers as the ABI.

Methods: From January through November 2006, 585 patients were screened for peripheral arterial disease. SFA DUS was included in this Institutional Review Board approved program and demographic/ultrasound data were collected prospectively. SFA DUS findings were divided into six categories. Plaque w/o color change or worse and ABI <0.90 or >1.20 were considered to be abnormal. Data were evaluated using decision matrix and logistical regression analysis.

Results: Sensitivity and specificity of SFA DUS using the ABI as the benchmark was 100% and 88%, respectively. Sensitivity and specificity of ABI was 17% and 100%, respectively, using DUS as the standard. DUS detected atherosclerotic disease in 143 SFAs (93 patients) in which the ipsilateral ABI was normal, and there were no false negative SFA DUS studies. Multivariate logistic regression analysis demonstrated the following variables to be significantly and independently associated with an abnormal SFA DUS as well as an abnormal ABI: history of claudication, history of myocardial infarction, and an abnormal carotid DUS. Additional variables (current or past smoker and age >55) were also independently associated with an abnormal SFA DUS but not with an abnormal ABI. Mean time to complete bilateral testing was essentially the same for both tests.

Conclusions: SFA DUS is an accurate screening tool and can be utilized in screening protocols in place of the time-honored ABI without prolonging the examination. Traditional vascular disease markers that are found in patients with an abnormal ABI are also associated with an abnormal SFA DUS. SFA DUS identifies more patients with early LE atherosclerosis than does ABI without missing significant popliteal/tibial artery occlusive disease. Finally, an abnormal SFA DUS can be used as an indirect marker to identify more potentially at risk patients with CAD.