title: Interobserver agreement on ultrasound measurements of residual vein diameter, thrombus echogenicity and Doppler venous flow in patients with previous venous thrombosis.
abstract: BACKGROUND
  In patients with new symptoms in a leg previously affected by deep vein thrombosis (DVT), the presence of thrombus on ultrasound cannot be assumed to be due to recurrent thrombosis. Several parameters have been suggested to differentiate between acute and chronic thrombus on ultrasound, including measurement of residual vein diameter during compression, thrombus echogenicity and Doppler assessment of venous flow, but studies on the reproducibility of these measurements are sparse.
  
  
  OBJECTIVE
  To determine interobserver agreement on measurement of residual vein diameter, thrombus echogenicity and Doppler venous flow in patients with residual thrombus in the veins of the lower limb.
  
  
  METHODS
  Patients with previous proximal DVT who had a high likelihood of residual thrombosis, but without symptoms of recurrent DVT, had ultrasound examinations independently performed by two examiners on the same day. Interobserver agreement on measurement of residual vein diameter, thrombus echogenicity and Doppler venous flow was evaluated.
  
  
  RESULTS
  We determined that interobserver agreement on these measurements was moderate. The mean difference between paired measurements of residual vein diameter was 2.2 mm (95th centile, 8.0 mm). When both examiners agreed residual thrombus was present, 54% of the variance of the measurement of residual vein diameter was accounted for by the paired measurements. The weighted kappa coefficient for thrombus echogenicity was 0.01 and for Doppler venous flow was 0.51.
  
  
  CONCLUSIONS
  The error associated with ultrasound measurements of residual vein diameter, thrombus echogenicity and flow appears to be considerable.
authors.affiliation: McMaster University, Hamilton, Ontario, Canada. llinkins@thrombosis.hhscr.org
authors.forename: Lori-Ann
authors.initials: LA
authors.lastname: Linkins
authors.forename: Richard
authors.initials: R
authors.lastname: Stretton
authors.forename: Linda
authors.initials: L
authors.lastname: Probyn
authors.forename: Clive
authors.initials: C
authors.lastname: Kearon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D013924:Thrombophlebitis / Q000473:pathology; D013927:Thrombosis / Q000175:diagnosis* / Q000473:pathology*; D013997:Time Factors; D014463:Ultrasonography; D018608:Ultrasonography, Doppler / Q000379:methods*; D020246:Venous Thrombosis / Q000150:complications* / Q000175:diagnosis / Q000473:pathology