Abstract P159: Repeatability of Automated Determinations of the Ankle Brachial Index The Atherosclerosis Risk in Communities (ARIC) Study
Background: The ankle brachial index (ABI) is a noninvasive and inexpensive means to assess peripheral arterial disease (PAD) with established validity. Low ABI values are predictive of cardiovascular morbidity and all-cause mortality. Automated, oscillometric devices are commonly used to measure ABI in clinical settings and population studies for time-efficiency and to reduce observer-dependent variability. The repeatability of multi-limb systolic blood pressure (SBP) and of ABI using oscillometric devices has not been evaluated in depth.
Objectives: Characterize the repeatability of limb-specific SBP and of ABI in a multi-center, community-based study of older adults.
Methods: A subset of ARIC study participants (n=79; 58% women) with a mean age of 75.7 years underwent two examinations 4-8 weeks apart, using standardized protocols. SBP in the arms and ankles was measured twice in each ‘visit’ in the supine position after a 5 minute rest, using the Omron Colin VP-1000 Plus system (Omron Co., Ltd., Kyoto, Japan). Right brachial SBP (RbSBP), left brachial SBP (LbSBP), right ankle SBP (RaSBP), left ankle (LaSBP), right ABI (RABI), and left ABI (LABI) were measured concurrently. Analyses excluded 3 individuals due to; ABI and SBP values >3 standard deviations away from the mean, body mass index > 40 kg/m2, major arrhythmias, and aortic stenosis. Random-effects analysis of variance was used to examine the deviation of within visit, between visit, and between-participant components from the grand mean. The intra-class correlation coefficient (ICC), the corresponding 95% confidence intervals (95% CI), minimal detectable change (MDC), and minimal detectable difference (MDD) were calculated.
Results: The grand means and standard deviations (SD) were 137.6 ± 16.5 mmHg for RbSBP, 138.2 ± 16.3 mmHg for LbSBP, 162.4 ± 23.6 mmHg for RaSBP, 161.8 ± 23.0 mmHg for LaSBP, 1.16 ± 0.11 for RABI, 1.15 ± 0.11 for LABI. Within-visit (instrument-related) variations were 9.0% for RbSBP, 9.6% for LbSBP, 12.6% for RaSBP, 10.1% for LaSBP, 22.7% for RABI, and 14.2% for LABI. The ICCs (95% CI) were 0.62 (0.49, 0.75) for RbSBP, 0.65 (0.53, 0.77) for LbSBP, 0.61 (0.48, 0.74) for RaSBP, 0.66 (0.55, 0.78) for LaSBP, 0.48 (0.34, 0.64) for RABI, and 0.61 (0.48, 0.73) for LABI. The MDC was 28.5 mmHg for RbSBP, 26.9 mmHg for LbSBP, 41.3 mmHg for RaSBP, 37.0 mmHg for LaSBP, 0.22 for RABI, and 0.20 for LABI. The MDD for two independent samples (N=100) was 8.5 mmHg for RbSBP, 8.4 mmHg for LbSBP, 12.2 mmHg for RaSBP, 11.8 mmHg for LaSBP, 0.06 for RABI and LABI.
Conclusion: The short-term (4-8 week) repeatabilities of automated, oscillometric measures of the arm and ankle SBP, and of the LABI are substantial. The MDC of the LABI is approximately 1.7 SD. The estimated repeatability of the RABI is moderate, and its MDD is 2 SD. The average duration of the automated measurements was 5 minutes and the examinees considered them to be comfortable.
Author Disclosures: A. Al-Qunaibet: None. M.L. Snyder: None. D. Couper: None. H. Tanaka: None. S. Cheng: None. K. Matsushita: None. A.R. Folsom: None. G. Heiss: None.
- © 2015 by American Heart Association, Inc.