title: The reliability of a single protocol to determine endothelial, microvascular and autonomic functions in adolescents.
abstract: BACKGROUND
  Impairments in macrovascular, microvascular and autonomic function are present in asymptomatic youths with clustered cardiovascular disease risk factors. This study determines the within-day reliability and between-day reliability of a single protocol to non-invasively assess these outcomes in adolescents.
  
  
  METHODS
  Forty 12- to 15-year-old adolescents (20 boys) visited the laboratory in a fasted state on two occasions, approximately 1 week apart. One hour after a standardized cereal breakfast, macrovascular function was determined via flow-mediated dilation (FMD). Heart rate variability (root mean square of successive R-R intervals; RMSSD) was determined from the ECG-gated ultrasound images acquired during the FMD protocol prior to cuff occlusion. Microvascular function was simultaneously quantified as the peak (PRH) and total (TRH) hyperaemic response to occlusion in the cutaneous circulation of the forearm via laser Doppler imaging. To address within-day reliability, a subset of twenty adolescents (10 boys) repeated these measures 90 min afterwards on one occasion.
  
  
  RESULTS
  The within-day typical error and between-day typical error expressed as a coefficient of variation of these outcomes are as follows: ratio-scaled FMD, 5·1% and 10·6%; allometrically scaled FMD, 4·4% and 9·4%; PRH, 11% and 13·3%; TRH, 29·9% and 23·1%; and RMSSD, 17·6% and 17·6%. The within- and between-day test-retest correlation coefficients for these outcomes were all significant (r > 0·54 for all).
  
  
  CONCLUSIONS
  Macrovascular, microvascular and autonomic functions can be simultaneously and non-invasively determined in adolescents using a single protocol with an appropriate degree of reproducibility. Determining these outcomes may provide greater understanding of the progression of cardiovascular disease and aid early intervention.
authors.affiliation: Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, EX1 2LU, UK.
authors.forename: Bert
authors.initials: B
authors.lastname: Bond
authors.affiliation: Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, EX1 2LU, UK.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Williams
authors.affiliation: Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, EX1 2LU, UK.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Barker
mesh_terms: D000293:Adolescent; D001341:Autonomic Nervous System / Q000502:physiology*; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000294:innervation; D055424:Cardiac-Gated Imaging Techniques; D002648:Child; D004562:Electrocardiography; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging* / Q000294:innervation; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D055806:Microvessels / Q000000981:diagnostic imaging* / Q000294:innervation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013997:Time Factors; D018608:Ultrasonography, Doppler; D014664:Vasodilation
keywords: flow-mediated dilation; heart rate Variability; novel CVD risk factors; reactive hyperaemia; young people