title: Brachial flow-mediated vasodilator responses in population-based research: methods, reproducibility and effects of age, gender and baseline diameter.
abstract: BACKGROUND
  Brachial artery ultrasound has been proposed as an inexpensive, accurate way to assess cardiovascular risk in populations. However, analysis and interpretation of these data are not uniform.
  
  
  METHODS
  We analysed the relationship between relative and absolute changes in brachial artery diameter in response to flow-mediated dilation and age, gender and baseline diameter among 4,040 ultrasound examinations from subjects aged 14 to 98 years.
  
  
  RESULTS
  Reproducibility studies demonstrated intra- and interreader and intrasubject correlations from 0.67 to 0.84 for repeated measures of per cent change in diameter. Per cent change in diameter after flow stimulus was 3.58 +/- 0.10% (mean +/- standard deviation). Corresponding values for baseline diameter and absolute change in diameter were 4.43 +/- 0.87 mm and 0.15 +/- 0.01 mm, respectively. Baseline diameter and its variance were inversely related to per cent change in diameter (P< 0.001). In contrast, absolute change in diameter was more uniform throughout the range of baseline diameters. Baseline diameter was directly related, and per cent change in diameter inversely related, to age (P < 0.001 for all three measures). Time to maximum vasodilator response increased with age (P < 0.001). Women (n=2,315) had significantly larger per cent change in diameter than men (n=1,725) (P < 0.001). However, after adjustment for age and baseline diameter, per cent and absolute change were 5% smaller in women than men (P < 0.05 for both). In multivariate analysis, age was overwhelmingly the most important determinant of absolute change in diameter (P < 0.001).
  
  
  CONCLUSIONS
  Automated analysis of brachial flow-mediated vasodilator responses is both feasible and reproducible in large-scale clinical and population-based research.
authors.affiliation: Department of Internal Medicine/Cardiology, Wake Forest University School Medicine, Winston-Salem, North Carolina 27157-1045, USA. kklein@wfubmc.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Herrington
authors.forename: L
authors.initials: L
authors.lastname: Fan
authors.forename: M
authors.initials: M
authors.lastname: Drum
authors.forename: W A
authors.initials: WA
authors.lastname: Riley
authors.forename: B E
authors.initials: BE
authors.lastname: Pusser
authors.forename: J R
authors.initials: JR
authors.lastname: Crouse
authors.forename: G L
authors.initials: GL
authors.lastname: Burke
authors.forename: M A
authors.initials: MA
authors.lastname: McBurnie
authors.forename: T M
authors.initials: TM
authors.lastname: Morgan
authors.forename: M A
authors.initials: MA
authors.lastname: Espeland
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001775:Blood Circulation / Q000502:physiology; D001916:Brachial Artery / Q000737:chemistry* / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011159:Population Surveillance / Q000379:methods*; D015203:Reproducibility of Results; D012737:Sex Factors; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology*; D014665:Vasodilator Agents / Q000627:therapeutic use*
chemical_list: D014665:Vasodilator Agents