Reproducibility of pulse-wave analysis and pulse-wave velocity determination in chronic kidney disease

Background. Indices of central arterial stiffness, derived by use of applanation tonometry, have shown to be strong independent predictors of cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD). The objective of this study was to evaluate the intra- and inter-observer and day-to-day reproducibility of pulse-wave analysis (PWA) and pulse-wave velocity (PWV) in pre-dialysis patients with CKD stages 35 using applanation tonometry with the SphygmoCor software and hardware. Methods. Double recordings of the radial pressure waveform and the aortic and brachial PWV were performed under standardized conditions in 19 CKD patients with a mean GFR 25.3 ml/min/1.73 m(2) (range 9.9-42.2) by two trained observers and repeated by one of the observers within a week. Results. The mean inter-observer and day-to-day differences (2 SD) for the augmentation index (AIx) were 0.9 +/- 15.8 and 2.6 +/- 11.2, for subendocardial viability ratio (SEVR) 0.9 +/- 15.5 and 0.4 +/- 24.7, for aortic pulse pressure (PP) 1.4 +/- 13.3 mmHg and 0.3 +/- 20.9 mmHg and for aortic PWV 0.3 +/- 3.2 m/s and 0.7 +/- 1.9 m/s, respectively. Intra-observer differences were calculated for each of three sets of double measurements and showed good reproducibility as well. Calculations on sample size needed in a clinical trial showed a limited number of patients needed in a clinical study over time. Conclusions. PWA and PWV based on applanation tonometry using the SphygmoCor software and hardware are highly reproducible in pre-dialysis patients with CKD with the day-to-day variation being in accordance with the intra- and inter-observer variation. Thus, applanation tonometry using the SphygmoCor system is a simple, non-invasive method to assess central haemodynamics in clinical trials in patients with pre-dialysis CKD with only a limited number of patients needed to detect significant differences.