title: Variability and reproducibility of carotid structural and functional parameters assessed with transcutaneous ultrasound - results from the SAPALDIA Cohort Study.
abstract: OBJECTIVE
  Carotid intima media thickness (CIMT) and local stiffness are vascular biomarkers of atherosclerotic burden. We investigated the variability and reproducibility of clinically relevant structural (CIMT, lumen diameter) and functional parameters (strain, distensibility, compliance, β-stiffness index, Peterson's elastic modulus and Young's elastic modulus) measured in B-mode ultrasound sequences of the common carotid artery in the second follow up of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases In Adults (SAPALDIA3).
  
  
  METHODS
  Ultrasound sequential images were examined twice over a 1 cm segment across at least one heart cycle in 165 SAPALDIA3 participants. To assess variability and reproducibility of structural and functional parameters, individual coefficients of variation (CV), intraclass correlation (ICC), Bland-Altman plots and mixed effect regressions were used.
  
  
  RESULTS
  ICCs of repeated examinations ranged between 0.67 and 0.77 for blood pressure indices, between 0.87 and 0.97 for structural properties and between 0.75 and 0.79 for functional parameters. CV was lowest in structural parameters (1.6-4.6%), followed by blood pressure (5.1-7.9%) and functional indices (11.0-13.1%). Variations in all parameters were predominantly explained by subjects (>74% in functional, >82% in structural properties). Bland-Altman plots for functional indices showed mean and standard deviation of the respective mean value of 4.2(19.6)% for strain, 1.9(24.4)% for distensibility, 2.4(22.2)% for compliance, 3.0(24.4)% for β-stiffness index, 0.9(25.7)% for Peterson's elastic modulus and 1.2(27.9)% for Young's elastic modulus.
  
  
  CONCLUSIONS
  The results show that SAPALDIA3 measurements of transcutaneous ultrasound examinations have an excellent reproducibility of structural parameters and a good reproducibility of functional indices.
authors.affiliation: Institute of Exercise and Health Sciences, Div. Sports and Exercise Medicine, University of Basel, Birsstrasse 320B, 4052 Basel, Switzerland. Electronic address: seraina.caviezel@unibas.ch.
authors.forename: Seraina
authors.initials: S
authors.lastname: Caviezel
authors.forename: Julia
authors.initials: J
authors.lastname: Dratva
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Schaffner
authors.forename: Alexandra
authors.initials: A
authors.lastname: Teynor
authors.forename: Manfred W
authors.initials: MW
authors.lastname: Baumstark
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Eric
authors.initials: E
authors.lastname: de Groot
authors.forename: Luc
authors.initials: L
authors.lastname: Burdet
authors.forename: Thomas
authors.initials: T
authors.lastname: Rothe
authors.forename: Marco
authors.initials: M
authors.lastname: Pons
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Gaspoz
authors.forename: Thierry
authors.initials: T
authors.lastname: Rochat
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
authors.forename: Nicole
authors.initials: N
authors.lastname: Probst-Hensch
authors.forename: Arno
authors.initials: A
authors.lastname: Schmidt-Trucksäss
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D002339:Carotid Arteries / Q000000981:diagnostic imaging* / Q000473:pathology*; D059168:Carotid Intima-Media Thickness; D015331:Cohort Studies; D055119:Elastic Modulus; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011379:Prognosis; D012044:Regression Analysis; D015203:Reproducibility of Results; D012306:Risk; D013557:Switzerland; D014463:Ultrasonography / Q000379:methods*
keywords: Arterial stiffness; Common carotid artery; Diameter; Intima media thickness; Reproducibility; Ultrasound