title: Carotid duplex imaging: variation and validation.
abstract: BACKGROUND
  Duplex imaging is increasingly used as the only investigation before carotid endarterectomy, but many different criteria exist in the literature for the detection of a severe (70-99 per cent) carotid stenosis. This study aimed to investigate current practice in carotid duplex imaging in Great Britain and Ireland.
  
  
  METHODS
  A postal questionnaire was sent to 86 vascular surgical units.
  
  
  RESULTS
  The median number of scans performed per year was 450 (range 60-4500). Thirty-six per cent of units who responded used peak systolic : end diastolic velocity ratio to calculate carotid stenosis. Overall, nine different major duplex criteria were used to grade carotid stenosis in 14 different systems of percentage bands. Only 51 per cent of units verified their duplex criteria against angiography. Eighteen per cent of units used two or more different types of duplex scanner and applied the same diagnostic criteria to each machine.
  
  
  CONCLUSIONS
  A wide variation in diagnostic duplex criteria and methods of grading stenosis exists among vascular units. Internal validation is not performed routinely. Standardization of duplex criteria would ensure greater consistency, but would not replace the need for validation of results within each unit.
authors.affiliation: Departments of Vascular Surgery and Radiology, Royal Berkshire Hospital, Reading RG1 5AN, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Perkins
authors.forename: R B
authors.initials: RB
authors.lastname: Galland
authors.forename: M J
authors.initials: MJ
authors.lastname: Simmons
authors.forename: T R
authors.initials: TR
authors.lastname: Magee
mesh_terms: D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000000981:diagnostic imaging*; D019538:Health Care Surveys; D006801:Humans; D007494:Ireland; D011364:Professional Practice; D012680:Sensitivity and Specificity; D018616:Ultrasonography, Doppler, Duplex / Q000592:standards; D006113:United Kingdom