Ultrasound Doppler enthesitis shows sensitivity to change after biological therapy in spondyloarthritis and psoriatic arthritis patients.

Objective: To explore the sensitivity to change in power Doppler (PD) enthesitis in active spondyloarthritis (SpA) and psoriatic arthritis (PsA) patients.
Method: This was a longitudinal study in patients with SpA and PsA with active disease [patients starting or switching to biological disease-modifying anti-rheumatic drugs (bDMARDs)]. The MAdrid Sonographic Enthesitis Index (MASEI) was performed at baseline and at 3 and 6 month visits. The MASEI and Outcome Measures in Rheumatology (OMERACT) PD enthesitis definitions were checked. Reliability analysis among three readers was performed with ultrasound (US)-recorded videos.
Results: US examinations of 25 patients were included; 16 (64%) had SpA and nine (36%) PsA. The median (interquartile range, IQR) age was 49 (41-61) years, and 13 patients (52%) were female. The median (IQR) 28-joint Disease Activity Score of 3.6 (2.3-4.2), Bath Ankylosing Spondylitis Disease Activity Index of 6.7 (6.1-7.4), and C-reactive protein value of 8.2 (1.6-20) reflected moderate to high disease activity at baseline. Both MASEI and OMERACT PD enthesitis improved significantly at 3 and 6 month follow-up (p < 0.05) and showed sensitivity to change (standard error of measurement = 0.47 and 0.61, respectively). Improvement in clinical activity outcomes was significantly associated with decreases in MASEI and OMERACT PD enthesitis counts (p < 0.05). The MASEI and OMERACT PD definitions had excellent reliability (kappa = 0.918 and 0.865, respectively).
Conclusion: PD enthesitis significantly improved at 3 and 6 month follow-up in patients undergoing bDMARD therapy. Both MASEI and OMERACT PD US enthesitis reflect response to treatment.