Abstract P183: Repeatability of Pulse Wave Velocity: The Atherosclerosis Risk in Communities (ARIC) Study
Authors: Snyder Michelle , Tanaka Hirofumi , Palta Priya , Patel Mehul , Camplain Ricky , Couper David , Cheng Susan , Al Qunaibet Ada , Poon Anna , Heiss Gerardo 
Published: July 2021

Background:
Despite the growing use of pulse wave velocity (PWV), a measure of arterial stiffness that is predictive of cardiovascular disease and all-cause mortality, the repeatability of central, lower-extremity, and composite measures of PWV has not been examined.

Objectives:
Characterize the repeatability of PWV in a multi-center, population-based study of older adults.

Methods:
We included a subset of the ARIC visit 5 (2011-2013) participants (n=79; mean age 75.7 years; 46 females) from the following four United States communities: Forsyth County, NC; Jackson, MS; Minneapolis, MN; and Washington County, MD who underwent two standardized exams 4-8 weeks apart. At each exam, trained and certified technicians obtained two PWV measurements following a standardized protocol using the VP-1000 Plus system (Omron Co., Ltd., Kyoto, Japan). Measurements included carotid-femoral PWV (cfPWV), right brachial-ankle PWV (baPWV) and right femoral-ankle PWV (faPWV). We excluded participants with evidence of a major arrhythmia on a 12-lead electrocardiogram, aortic stenosis, body mass index >40 kg/m
2
, and excluded PWV values >3 standard deviations away from the mean. We used random-effects mixed models to parse the variance of the measures into their between-participant, between-visit, and within-visit components, then calculated the intra-class correlation coefficient (ICC) and estimated the number of replicates needed to achieve an ICC of 0.9 using the Spearman-Brown formula and the lower bound of the ICC 95% confidence interval (95% CI). We also calculated the minimal detectable change (MDC; 95% confidence) and minimal detectable difference (MDD).

Results:
Between-participant variation accounted for 69% to 84% of the total variation in cfPWV, baPWV and faPWV. The ICCs (95% CIs) were 0.70 (0.59, 0.81) for cfPWV, 0.84 (0.78, 0.90) for baPWV, and 0.69 (0.59, 0.79) for faPWV. The number of replicates to achieve an ICC of 0.90 was 6 for cfPWV and faPWV and 3 for baPWV. The overall means and standard deviations (SD) were 1,198.9 ± 269.6 cm/s for cfPWV, 1,742.0 ± 328.3 cm/s for baPWV, and 1,063.4 ± 189.4 cm/s for faPWV. The MDC between repeat measures within an individual was 411.0 cm/s for cfPWV, 370.6 cm/s for baPWV, and 301.4 cm/s for faPWV. The MDD for two independent samples of 100 per group was 139.3 cm/s for cfPWV, 172.3 cm/s for baPWV, and 100.4 cm/s for faPWV.

Conclusion:
The repeatability is excellent for baPWV and fair for cfPWV and faPWV. The MDC was approximately 1 SD for baPWV and 1.5 SDs for cfPWV and faPWV and the MDD for 100 per group was approximately 0.5 SD for cfPWV, baPWV and faPWV. Averaging replicates would reduce the effects of measurement variability. These results support the use of PWV in clinical and epidemiologic studies; however, to minimize potential bias, studies need to consider measurement variability in design development and in the analysis and interpretation of results.