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The ABI: Standardizing Measurements & Interpretations

The ABI: Standardizing Measurements & Interpretations

When the ankle-brachial index (ABI) emerged in 1950, it was initially proposed for use as a noninvasive diagnostic tool for lower-extremity peripheral artery disease (PAD). Since then, studies have shown that the ABI is an indicator of atherosclerosis at other vascular sites, making it a useful prognostic marker for cardiovascular events and functional impairment, even in the absence of symptoms of PAD. In an issue of Circulation, the American Heart Association (AHA) released a scientific statement with standardized recommendations for measuring and monitoring the ABI. The recommendations provide protocols and thresholds for use in PAD and cardiovascular risk prediction, according to Michael H. Criqui, MD, MPH, FAHA, who co-chaired the writing committee that developed the scientific statement. “A lack of standards for measuring and calculating the ABI can lead to discrepancies that can significantly impact both prevention and treatment of cardiovascular disease,” he says. “The estimated prevalence of PAD may vary substantially according to the mode of ABI calculation.” Reducing Variation in ABI Technique Recent studies have revealed that techniques for performing the ABI vary from clinician to clinician. Several variables have been identified, including the position of patients during measurement, the sizes of the arm and leg cuffs, and the method of pulse detection over the brachial artery and at the ankles. Other variables include whether the arm and ankle pressures were measured bilaterally, which ankle pulses were used, and whether a single measure or replicate measures were obtained. Several recommendations have been endorsed by the AHA for measuring the ABI (Table 1). “These recommendations can serve as a guide to ensure that clinicians are measuring the ABI...
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