Ultrasound for assessing disease activity and structural damage in psoriatic arthritis: the UPsA scores from a multicentre study by the Italian Society of Rheumatology.

OBJECTIVES

As part of the ultrasound in psoriatic arthritis (PsA) treatment (Ultrasound in Psoriatic Arthritis Treatment-NCT03330769) study, 2 ultrasound scores for PsA (UPsA)-the UPsA activity score and the UPsA damage score-were developed and internally validated to assess musculoskeletal inflammation and structural damage in PsA. In addition, a simplified UPsA activity score (sUPsA) was also derived to enhance feasibility and applicability in routine clinical practice.

METHODS

Baseline and 6-month data from patients with PsA across 19 Italian centres were analysed. Clinical evaluations included joint counts, enthesitis, dactylitis, and patient-reported outcomes. Ultrasound assessments, performed by trained sonographers, covered 42 joints, 36 tendons, 12 entheses, and 2 bursae. Factor analysis was used to derive composite scores (range 0-10). Construct validity was assessed by Spearman's correlations with clinical variables, and sensitivity to change was evaluated using the standardised response mean (SRM).

RESULTS

A total of 312 patients with PsA were enrolled. The mean UPsA activity score was 3.7 (SD 1.86), correlating with Disease Activity for Psoriatic Arthritis (rs = 0.42), 68-tender joint count (rs = 0.31), and 66-swollen joint count (rs = 0.45; all P < .001). The UPsA damage score averaged 4.1 (SD 2.26), correlating with the modified Sharp-van der Heijde score (rs = 0.36, P < .001). The UPsA activity score showed moderate sensitivity to change overall (SRM = 0.63) and high responsiveness in patients achieving minimal disease activity (SRM = 1.03). The sUPsA retained 90% of the information from the full score while substantially improving feasibility.

CONCLUSIONS

The UPsA scores underwent internal validation and demonstrated responsiveness, representing valuable tools to assess PsA activity and damage.