Reliability of different Doppler ultrasound quantification methods and devices in the assessment of therapeutic response in arthritis

Objective. To evaluate the metric qualities of power Doppler ultrasound (PDUS) for different quantification methods and devices in the assessment of arthritis during anti-inflammatory treatment Methods. Twenty-four patients with active arthritis and first-time treatment with the TNF-alpha inhibitor adalimumab underwent sequential clinical, laboratory and US examination at baseline, weeks 2, 6 and 12. 2D and 3D PDUS was performed by two independent investigators. The images and movies were scored from 0 to 3 and the amount of colour pixels and voxels was calculated. In addition, the resistance index of a synovial artery was measured. Thirteen patients were examined with a second US machine. Results. Treatment response was already observed at week 2 with a significant reduction of 2D (P < 0.01) and 3D scores (P < 0.001). A moderate correlation to 28-joint disease activity score was found for 3D voxel count (r(s) = 0.35, P < 0.001). Interobserver agreement was k or ICC >= 0.8 for all methods except the resistance index (ICC = 0.60). Intermachine agreement was 0.57 for 2D PDUS score. Conclusions. The study demonstrates good to excellent interobserver and moderate intermachine reliability of different PDUS assessment methods in a longitudinal open-label study.