Arthralgia and Ultrasound Characteristics of Subclinical Psoriatic Arthritis: A Cross-Sectional Study Based on the SPAWCH Cohort.

As a critical stage before psoriatic arthritis (PsA) onset, subclinical PsA provides an opportunity window for early diagnosis and intervention. This study aimed to describe the clinical and ultrasound characteristics of patients fulfilling the EULAR definition of subclinical PsA, and to explore the heterogeneity of arthralgia within this population. Patients fulfilling the EULAR definition of subclinical PsA, characterized by arthralgia and/or ultrasound evidence of synovial/entheseal inflammation without clinical synovitis, were enrolled in the Subclinical Psoriatic Arthritis Cohort of West China Hospital (SPAWCH) Cohort from January 2019 to December 2024. We collected clinical information, arthralgia features, and ultrasound findings, conducting a cross-sectional analysis. Overall, 306 patients were included in the analysis. Among them, 84 (27.5%) had both arthralgia and ultrasound abnormalities (Group AU), 203 (66.3%) had isolated ultrasound abnormalities (Group IU), and 19 (6.2%) had isolated arthralgia (Group IA). Compared with the Group IU, patients in the Group AU were older (49.3 ± 13.7 vs. 43.5 ± 13.2 years, p = 0.001) and had a longer duration of psoriasis (17.7 ± 12.3 vs. 14.1 ± 9.8 years, p = 0.020). Additionally, the two main arthralgia types were activity-related (60, 58.3%) and rest-related (25, 24.3%). Rest-related arthralgia was associated with prolonged arthralgia duration (p = 0.041), higher morning stiffness incidence (p = 0.031), and more prominent inflammatory characteristics (p = 0.001) compared to activity-related cases. In this study, ultrasound abnormalities emerged as the dominant feature in patients meeting the EULAR definition of subclinical PsA. Notably, the coexistence of arthralgia and ultrasound abnormalities was associated with a longer duration of psoriasis. While activity-related arthralgia was the most prevalent type, rest-related arthralgia.