Assessement of repeatability of aortic pulse wave velocity measurements

Abstract

Background Pulse wave velocity (PWV) measurement is simple and non-invasive method to assess arterial stiffness, with prognostic value. The aim of the study was to assess PWV measurement repeatability.
Material nad methods The study population consists of 206 people, in whom one investigator performed two consecutive carotid-femoral PWV measurements, the first and immediately the second (PWV₁, and PWV₂, respectively). Measurement repatability was assessed using Bland and Altman method, by calculation correlation coefficient between results of the first and the second measurement, and by calculating intraclass correlation coefficient (ICC). For each pair of measurements the difference was calculated (D = PWV₁ - PWV₂), than mean D (D_śr.) and its standard deviation (SD) were calculated. The limits of agreement were determined as D_śr. ± 2SD.
Results For 92,7% pairs of measurement the difference was lower than limits of agreement, while according to British Standards Intitution 95% of differences to be less than two standard deviations. Statistically significant correlation was found between results of PWV₁ and PWV₂ in the study population: r = 0.89 (p < 0.00001), and ICC was 0.86. The size of the difference was correlated to blood pressure before first PWV measurement; the higher blood pressure, PWV₂ was more lower than PWV₁.
Conclusions Despite strong correlation between PWV measurements performed by one investigator, this method has no met criteria of high repeatibility. High blood pressure is one of the causes of difference between measurements.