1. USPSTF Recommendation Statement Summary: No recommendation. There is insufficient data for the use of ankle-brachial index (ABI) as a screening test for peripheral arterial disease (PAD) in preventing cardiovascular morbidity and mortality for asymptomatic patients who do not have a known diagnosis of vascular disease, severe chronic kidney disease or diabetes.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Cardiovascular disease (CVD) is the leading cause of death in North America. Early CVD is commonly an asymptomatic condition, and consequently, the need for a reliable screening test may allow for early detection and, ultimately, improved outcomes. The ankle-brachial index (ABI) is used for assessing the presence and severity peripheral arterial disease (PAD) in the clinical setting. Given that there is a well-established association between PAD and coronary atherosclerosis, detection of PAD with screening ABIs in asymptomatic individuals may be a marker of early CVD that could benefit from early intervention. However, the evidence for the use of ABI as a screening tool in asymptomatic adults is not clear. In 2009, the United States Preventive Services Task Force (USPSTF) found insufficient evidence to make a definitive recommendation. This year, the USPSTF has released a new recommendation statement based on a systematic review of the most current evidence. The review excluded patients with diabetes, known vascular disease or chronic kidney disease. Based on this review, the USPSTF concluded that there is currently still inadequate evidence that ABI screening and early treatment of PAD in asymptomatic individuals leads to clinically important benefits or harms (no recommendation). However, a relatively small evidence base was reviewed, and thus, further studies need to be performed in this area. In particular, large, population-based, randomized trials are needed to determine whether screening for PAD with ABI improves clinical outcomes.
In-Depth [systematic review]: The systematic review sought to explore the impact of ABI on morbidity and mortality independently of Framingham risk score. To do this, a review of MEDLINE and Cochrane central registrar of controlled trials was performed from 1996 to Sept 2012. Study abstracts were independently reviewed by two investigators using predetermined criteria to determine if the full article warranted reading. In case of discrepancy, a third investigator was consulted. From this, 4434 abstracts and 418 full-text articles were reviewed. 17 studies in total were used to examine the predictive value of ABI, including treatment benefits and harms. Due to the limited number of studies, data was qualitatively instead of quantitatively summarized. This review identified 1 study that suggested ABI could be used along with FRS to reclassify 10-year CAD risk but also identified 4 subsequent studies that provided evidence against this concept. This led to the conclusion that ABI shows limited utility in the general asymptomatic population, although there may be subsets for which it may be useful. Furthermore, this article goes on to suggest that after a review of the literature evidence for the treatment of asymptomatic individuals identified via ABI needs to be studied further.
By Adam Whittington and Aimee Li, MD
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