title: Reproducibility of carotid-femoral pulse wave velocity in end-stage renal disease patients: methodological considerations.
abstract: BACKGROUND
  In end-stage renal disease (ESRD) patients, increased arterial stiffness detected by carotid-femoral pulse wave velocity (cf-PWV) is associated with fatal cardiovascular events and all-cause mortality. Since cf-PWV is an operator-dependent technique, poor reproducibility may be a source of bias in the estimation of arterial stiffness.
  
  
  OBJECTIVE
  We assessed the week-to-week reproducibility of cf-PWV and radial artery pulse wave analysis in healthy subjects and ESRD patients. We also determined the extent of patient eligibility, enrollment, acceptance, and comfort.
  
  
  METHODS
  In a cohort study design, independent tonometric examinations of carotid, femoral, and radial arteries were conducted in 20 healthy subjects and 15 ESRD patients attending chronic hemodialysis treatments according to a randomized sequence by two operators on 2 days scheduled 1-week apart. cf-PWV, augmentation index (AIx@HR75) and central pulse pressure (CPP) were the outcome measures. Patients were tested at mid-week and prior to dialysis treatment. The variability on the distance measured between the suprasternal notch and femoral site using two different methods (standard vs direct) was compared. A post-examination survey assessed acceptance and comfort associated with examinations. Reproducibility was evaluated by intra-class correlations (ICCs).
  
  
  RESULTS
  The mean age for healthy subjects and ESRD patients was 45 ± 12 and 63 ± 16 years, respectively. ESRD patients had higher cf-PWV (p = 0.0002), elevated AIx@HR75 (p = 0.003), and increased CPP (p = 0.001) compared to healthy subjects. The mean inter-visit differences for all stiffness indices were non-significant (p > 0.05), but the mean inter-operator differences for the cf-PWV were significant only in the healthy subject group (-0.7 m/s; p = 0.02). The ICCs between operators and visits were higher for the ESRD group compared to the healthy subjects (between operators, 0.870 vs 0.461; between visits, 0.830 vs 0.570). Distances were longer (p < 0.001), but less variable with the standard method compared to the direct method (healthy subjects, p = 0.036; ESRD, p = 0.39). There was a high rate of patient acceptance and minimal discomfort.
  
  
  CONCLUSIONS
  Week-to-week measurements of cf-PWV and pulse wave analysis are highly reproducible in ESRD patients prior to hemodialysis treatment. The high reproducibility and minimal test-to-test variations encourage use of cf-PWV to monitor changes in arterial stiffness and the efficacy of interventions in ESRD patients.
  
  
  BACKGROUND
  ClinicalTrials.gov, NCT02196610.
authors.affiliation: Department of Medicine, The Ottawa Hospital, University of Ottawa, Centre for Practice-Changing Research, Room L-2217, 501 Smyth Road, Ottawa, ON K1H 8L6 Canada ; The Ottawa Methods Centre, Ottawa Hospital Research Institute, Centre for Practice-Changing Research, 501 Smyth Road, Ottawa, ON K1H 8L6 Canada.
authors.forename: Rosendo A
authors.initials: RA
authors.lastname: Rodriguez
authors.affiliation: Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada.
authors.forename: Valerie
authors.initials: V
authors.lastname: Cronin
authors.affiliation: The Ottawa Methods Centre, Ottawa Hospital Research Institute, Centre for Practice-Changing Research, 501 Smyth Road, Ottawa, ON K1H 8L6 Canada.
authors.forename: Timothy
authors.initials: T
authors.lastname: Ramsay
authors.affiliation: Division of Nephrology, Department of Medicine, The Ottawa Hospital, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada ; Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada.
authors.forename: Deborah
authors.initials: D
authors.lastname: Zimmerman
authors.affiliation: Division of Nephrology, Department of Medicine, The Ottawa Hospital, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada ; Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada.
authors.forename: Marcel
authors.initials: M
authors.lastname: Ruzicka
authors.affiliation: Division of Nephrology, Department of Medicine, The Ottawa Hospital, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada ; Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, ON K1H 7W9 Canada.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Burns
keywords: Aortic stiffness; End-stage kidney disease; Inter-observer variation; Validation studies