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.
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.
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.
The error associated with ultrasound measurements of residual vein diameter, thrombus echogenicity and flow appears to be considerable.