title: Intersonographer reproducibility and intermethod variability of ultrasound measurements of carotid artery stenosis: The Tromsø Study.
abstract: OBJECTIVE
  Knowledge of the reproducibility of a diagnostic method is important in order to evaluate its usefulness. Few studies have examined interobserver and intermethod agreement on ultrasound measurements of carotid stenosis.
  
  
  METHODS
  Intersonographer agreement on ultrasound measurements of carotid plaque morphology and the estimated degree of stenosis by three ultrasound methods were assessed in a random sample of 51 participants with stenotic carotid arteries selected from a population health survey. The degree of stenosis was assessed by measurements of velocity, lumen diameter reduction and cross-sectional lumen area. Intermethod agreement on the degree of carotid stenosis was also assessed.
  
  
  RESULTS
  Agreement on plaque echogenicity and heterogeneity was moderate (kappa = 0.56 and kappa = 0.60, respectively). The mean degree of stenosis and median absolute difference between observers of the estimated degree of stenosis by the velocity method were 46.3 and 10.8%, respectively. The corresponding values were 51.0 and 5.8% for the diameter method, and 57.1 and 7.2%, for the cross-sectional lumen method. The limits of agreement for intersonographer reproducibility varied between +/-19.7 and 26.5%. For all methods, reproducibility increased with increasing degree of stenosis. Differences between the methods were large in low-grade stenosis but were acceptable in high-grade stenosis.
  
  
  CONCLUSIONS
  Considerable differences in ultrasound measurement of stenosis, which could lead to different clinical conclusions, were regularly encountered no matter what ultrasound method was used.
authors.affiliation: Institute of Community Medicine and Institute of Clinical Medicine, University of Tromsø, Norway. Ellisiv.Mathiesen@ism.uit.no
authors.forename: E B
authors.initials: EB
authors.lastname: Mathiesen
authors.forename: O
authors.initials: O
authors.lastname: Joakimsen
authors.forename: K H
authors.initials: KH
authors.lastname: Bønaa
mesh_terms: D000328:Adult; D000368:Aged; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway; D015588:Observer Variation; D012044:Regression Analysis; D015203:Reproducibility of Results; D014463:Ultrasonography