Automated determination of the ankle-brachial index using an oscillometric blood pressure monitor: validation vs. Doppler measurement and cardiovascular risk factor profile

Abstract

The ankle-brachial index (ABI) is a method used widely for peripheral arterial disease (PAD) diagnosis and cardiovascular risk prediction. This study validated automated ABI measurements taken using an oscillometric blood pressure (BP) monitor allowing simultaneous arm-leg BP measurements. A total of 93 patients (hypertension 83%; dyslipidemia 72%; diabetes 45%; cardiovascular disease 23%; smoking 15%) were submitted to Doppler and automated ABI measurements, performed using a professional oscillometric BP monitor (Microlife WatchBP Office; triplicate simultaneous arm-leg BP measurements), in a randomized order. The mean difference between the Doppler reading (1.08 ± 0.17) and (1) the first oscillometric ABI reading was 0.03 ± 0.11, (2) the average of two oscillometric readings was 0.02 ± 0.10 and (3) the average of three oscillometric readings was 0.02 ± 0.09 (P < 0.01 for all). Strong correlations were found between oscillometric and Doppler ABI (r 0.80, 0.85 and 0.86 for single and average of two and three oscillometric readings, respectively; P < 0.001 for all). Agreement between oscillometric and Doppler ABI in diagnosing PAD (Doppler ABI < 0.9) was found in 95% of cases (κ 0.79; agreement in diabetics: 94%, κ 0.79). A receiver operating characteristic (ROC) curve revealed area under the curve at 0.98, with a 0.97 oscillometric ABI cutoff for optimal sensitivity (92%) and specificity (92%) in diagnosing PAD. Average time for automated ABI measurement was 5.8 vs. 9.3 min for Doppler (P < 0.001). Doppler and oscillometric ABI were associated and predicted (multivariate regression analysis) by the same cardiovascular risk factors (pulse pressure, smoking and cardiovascular disease history). Automated ABI measurement using a professional BP monitor allowing simultaneous arm-leg BP measurements appears to be a reliable and faster alternative to Doppler measurement.