Ankle-arm index is a useful test for clinical practice in outpatients with suspected coronary artery disease

Background: Although a low ankle-arm index (AAI) has been reported to be associated with increased risk of cardiovascular mortality in several populations, no data exist concerning the impact of AAI for outpatients with suspected coronary artery disease (CAD) in the clinical setting. Methods and Results: The present study enrolled 840 outpatients (age range 35-87 years, mean age 63.9±10.2) with suspected CAD. All patients underwent AAI measurements and coronary angiography, and based on the AAI values, they were divided into group A (AAI <0.9; n=191; CAD positive, 181) and group B (AAI ≥0.9; n=649; CAD positive, 509). Metabolic syndrome (MS), obesity, and level of the inflammatory biomarker high sensitive C-reactive protein (hsCRP) were compared between the 2 groups. The sensitivity, specificity, positive and negative predictive values in predicting CAD with an AAI value <0.9 in all patients were 26.2%, 93.3%, 94.8% and 21.6%, respectively. The patients in group A was significantly older and there was a higher female-to-male ratio than in group B. The presence of hypertension and diabetes mellitus, current smoking status, and levels of low density lipoprotein (LDL)-cholesterol level, uric acid and hsCRP differed significantly between the 2 groups. Group A had a higher percentage of high LDL-cholesterol level, high waist-to-hip ratio and more positive cases of MS than group B. Multivariate logistical regression analysis showed that AAI was related to MS, high levels of hsCRP (>3 mg/L) and uric acid (>7 mg/dl) with odds ratios of 1.769, 3.907 and 2.580, respectively. Conclusions: The AAI test is an effective tool in predicting CAD in outpatients in clinical practise.