title: Stability and reproducibility of brachial artery flow-mediated dilation.
abstract: OBJECTIVE
  Brachial artery flow-mediated dilation (BAFMD) is a noninvasive technique, which has been suggested as a potential means of identifying patients with early atherosclerosis and therefore has enormous clinical appeal. Despite this, the stability and reproducibility of this technique are not yet clear. Therefore, the purpose of this study was to establish the stability and reproducibility of BAFMD after 5 min of forearm occlusion and to produce power calculations to aid in clinical trial design.
  
  
  METHODS
  Twenty-six healthy volunteers underwent high-resolution ultrasonographic brachial artery assessments before, during, and after 5 min of forearm occlusion. The study design involved three scans on 2 d, performed by two ultrasonographers and analyzed by two readers. All subjects were tested between 7 and 11 a.m. after refraining from food and exercise. The nondominant arms were scanned, in longitudinal view, approximately 4 cm proximal to the olecranon process, in the anterior/medial plane. Blood draws were performed on each visit. The SAS MIXED restricted maximum likelihood (REML) procedure for an unbalanced design was used to calculate variance components and provide power calculations.
  
  
  RESULTS
  Average baseline artery diameter for all studies was 3.48 +/- 0.53 mm. This increased to 3.71 +/- 0.57 mm (6.58 +/- 4.15%) at peak dilation. Intraclass correlation coefficients (ICCC) for days, testers, and readers were 0.92, 0.94, and 0.90, respectively. To detect a difference in vasoreactivity of 60% (two-tailed), e.g., 5% vasodilation versus 8% vasodilation, at 90% power, 23 and 10 subjects would be required for cross-sectional and pre-post designs, respectively.
  
  
  CONCLUSIONS
  These data indicate adequate stability and reproducibility of the BAFMD technique under controlled conditions. Additionally, BAFMD appears useful to differentiate between groups, although its prognostic value for the examination of individuals is unclear.
authors.affiliation: Department of Kinesiology, Louisiana State University, Baton Rouge 70803, USA. mwelsch@lsu.edu
authors.forename: Michael A
authors.initials: MA
authors.lastname: Welsch
authors.forename: Jason D
authors.initials: JD
authors.lastname: Allen
authors.forename: James P
authors.initials: JP
authors.lastname: Geaghan
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000502:physiology; D003430:Cross-Sectional Studies; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D010991:Plethysmography / Q000379:methods / Q000592:standards; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014664:Vasodilation / Q000502:physiology*