title: Flow-mediated dilatation of the brachial artery is a poorly reproducible indicator of microvascular function in Type I diabetes mellitus.
abstract: BACKGROUND
  Flow-mediated dilatation (FMD) of the brachial artery is commonly measured as a surrogate marker of endothelial function. Its measurement is, however, technically demanding and reports regarding its reproducibility have not always been favourable.
  
  
  OBJECTIVE
  Two Type I diabetes and control group comparator studies were conducted to assess the reproducibility of FMD and to analyse blood flow data normally discarded during FMD measurement.
  
  
  METHODS
  The studies were sequential and differed only with regard to operator and ultrasound machine. Seventy-two subjects with diabetes and 71 controls were studied in total.
  
  
  METHODS
  Subjects had FMD measured conventionally. Blood velocity waveforms were averaged over 10 pulses post forearm ischaemia and their component frequencies analysed using the wavelet transform, a mathematical tool for waveform analysis. The component frequencies were grouped into 11 bands to facilitate analysis.
  
  
  RESULTS
  Subjects were well-matched between studies. In Study 1, FMD was significantly impaired in subjects with Type I diabetes vs. controls (median 4.35%, interquartile range 3.10-4.80 vs. 6.50, 4.79-9.42, P < 0.001). No differences were detected between groups in Study 2, however. However, analysis of blood velocity waveforms yielded significant differences between groups in two frequency bands in each study.
  
  
  CONCLUSIONS
  This report highlights concerns over the reproducibility of FMD measures. Further work is required to fully elucidate the role of analysing velocity waveforms after forearm ischaemia.
authors.affiliation: Department of Therapeutics and Pharmacology, Queen's University Belfast, Belfast, BT9 7BL, UK. pk_hamilton@yahoo.co.uk
authors.forename: P
authors.initials: P
authors.lastname: Hamilton
authors.forename: C J
authors.initials: CJ
authors.lastname: Lockhart
authors.forename: A J
authors.initials: AJ
authors.lastname: McCann
authors.forename: C E
authors.initials: CE
authors.lastname: Agnew
authors.forename: M T
authors.initials: MT
authors.lastname: Harbinson
authors.forename: V
authors.initials: V
authors.lastname: McClenaghan
authors.forename: C
authors.initials: C
authors.lastname: Bleakley
authors.forename: R C
authors.initials: RC
authors.lastname: McGivern
authors.forename: G
authors.initials: G
authors.lastname: McVeigh
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D012039:Regional Blood Flow / Q000502:physiology; D015203:Reproducibility of Results; D014463:Ultrasonography; D014664:Vasodilation / Q000502:physiology*