Disease activity at the entheses and joints are correlated in psoriatic arthritis when explored with ultrasound

The aim of this study is to explore the link between the severity of the joint and entheses involvement in psoriatic arthritis (PsA) using musculoskeletal ultrasound (US).PsA patients from two centres in the Psoriatic Arthritis International Database (PsArt-ID) (n=126) underwent an ultrasound assessment of 46 joints and 12 large entheses. The correlation between joint and enthesitis scores on the US was analysed, in addition to the clinical indices versus the US.Grey-scale (GS) synovitis score for the joints was moderately correlated with the total enthesitis score (r=0.410, p<0.001). The Global Outcome Measure in Rheumatology in Clinical Trials-European League Against Rheumatism Synovitis Score (GLOESS) score was also found in correlation with the total enthesitis score (r=0.400, p<0.001). The link between the US and clinical examination findings only showed a poor correlation between swollen joint counts (SJC) and joint-US scores (r=0.298, p=0.001 for GLOESS). Assessment of the entheses on US showed a poor-moderate correlation between the entheseal damage scores and tender joint counts (TJC) (r=0.217, p=0.018) and SJC (r=0.326, p<0.001). In terms of the clinical examination and activity parameters, none of the clinical parameters and acute phase reactants were correlated to Leeds Enthesitis Index.Our study showed a link between the severity of the sonographic findings in the joints and the entheses. Imaging using US to assess enthesitis in clinical trials may improve our understanding on the role of enthesitis in disease pathogenesis.