Modification of a sonographic enthesitis score to differentiate between psoriatic arthritis and young healthy volunteers.

Objectives: We aimed to describe sonographic structural and inflammatory changes in entheses of patients with recently diagnosed psoriatic arthritis (PsA), patients with established PsA, and young healthy volunteers, and to investigate whether the MAdrid Sonographic Enthesitis Index (MASEI) enables us to distinguish these groups in an extreme comparison.Method: New and established PsA patients and healthy volunteers (aged 20-30years) were recruited. The triceps, quadriceps, patellar, Achilles and elbow extensor tendon insertion, and plantar fascia entheses were investigated sonographically for structural changes, erosions, calcifications, increased thickness, bursitis, and power Doppler (PD) signal according to the MASEI.Results: The study included 25 new and 25 established PsA patients, and 25 healthy volunteers. Increased thickness and PD signal in knee entheses were common for patients and healthy volunteers, while changes at other locations predominantly occurred in patients only. PD was recoded (1, one spot; 1.5, two or three spots; 2, confluent signal; 3, severe confluent signal) and thickness of knee entheses excluded. This resulted in different modified MASEI scores between PsA patients and young healthy controls: median (interquartile range) modified MASEI of 13 (10-22.5) in new PsA, 13.5 (9.5-18) in established PsA, and 3 (1-8.5) in healthy volunteers (p=0.002).Conclusions: Structural ultrasound changes and PD in entheses are common in both new and established PsA and healthy controls. MASEI score did not differentiate PsA patients from young healthy volunteers. After recoding of PD severity and excluding thickness of knee entheses, marked differences between PsA patients and healthy controls were observed.