Automated oscillometric measurement of the ankle-brachial index in patients with coronary artery disease

Abstract

Automated oscillometric ankle-brachial index (ABI) devices were designed to measure ABI in a primary-care setting to increase the peripheral artery disease (PAD) detection rate. However, ABI measurements obtained with an automated oscillometric device may differ from those obtained using a standard ultrasound Doppler method in the general population. The purpose of this study was to compare PAD detection by the Doppler method and the automated WatchBP Office ABI system in a high-risk population with coronary artery disease (CAD). Eighty consecutive patients with confirmed CAD were included. ABI was measured by automated oscillometry followed by conventional Doppler evaluation. PAD was defined as an ABI≤0.9. Each lower extremity was analyzed separately. The Doppler method detected an ABI≤0.9 in 56 lower extremities, whereas the automated method detected an ABI≤0.9 in 28 lower extremities (P<0.0001). A Bland-Altman plot showed poor agreement between the two methods. The mean ABI values obtained by the automated and Doppler methods were significantly different (1.11±0.20 vs. 0.95±0.24; P<0.00001). The sensitivity of the automated ABI device in detecting an ABI≤0.9 was 46.3% and the specificity was 98.0%. The positive and negative predictive values for diagnosing an ABI≤0.9 using the automated oscillometric method were 92.8% and 76.9%, respectively. In conclusion, the automated WatchBP Office ABI system should be used with caution for PAD detection and screening in patients with CAD, and this system should not replace the Doppler method in populations at high risk of cardiovascular disease.