Objectives The main objective was to generate a GLobal OMERACT Ultrasound DActylitis
Score (GLOUDAS) in psoriatic arthritis and to test its reliability. To this end, we
assessed the validity, feasibility and applicability of ultrasound assessment of finger
entheses to incorporate them into the scoring system.Methods The study consisted of
a stepwise process. First, in cadaveric specimens, we identified enthesis sites of
the fingers by ultrasound and gross anatomy, and then verified presence of entheseal
tissue in histological samples. We then selected the entheses to be incorporated into
a dactylitis scoring system through a Delphi consensus process among international
experts. Next, we established and defined the ultrasound components of dactylitis
and their scoring systems using Delphi methodology. Finally, we tested the interobserver
and intraobserver reliability of the consensus- based scoring systemin patients with
psoriatic dactylitis.Results 32 entheses were identified in cadaveric fingers. The
presence of entheseal tissues was confirmed in all cadaveric samples. Of these, following
the consensus process, 12 entheses were selected for inclusion in GLOUDAS. Ultrasound
components of GLOUDAS agreed on through the Delphi process were synovitis, tenosynovitis,
enthesitis, subcutaneous tissue inflammation and periextensor tendon inflammation.
The scoring system for each component was also agreed on. Interobserver reliability
was fair to good (kappa 0.39-0.71) and intraobserver reliability good to excellent
(kappa 0.80-0.88) for dactylitis components. Interobserver and intraobserver agreement
for the total B-mode and Doppler mode scores (sum of the scores of the individual
abnormalities) were excellent (interobserver intraclass correlation coefficient (ICC)
0.98 for B-mode and 0.99 for Doppler mode; intraobserver ICC 0.98 for both modes).Conclusions
We have produced a consensus-driven ultrasound dactylitis scoring system that has
shown acceptable interobserver reliability and excellent intraobserver reliability.
Through anatomical knowledge, small entheses of the fingers were identified and histologically
validated.
