Evaluating disease activity in established psoriatic arthritis with ultrasound

Abstract Background/Aims Early diagnosis, tight disease activity control and a treat-to-target approach are now recognised as critical factors that improve the outcome of patients with psoriatic arthritis (PsA). The traditional method used to assess disease activity is clinical examination (CE) by counting the number of tender and swollen joints. Ultrasound (US) has proven its superiority over CE for assessing the presence of synovitis in some studies. We aimed to identify the frequency and location of subclinical synovitis in a cohort of PsA patients with established disease. Methods Patients with established PsA were recruited. All gave informed, written consent and local ethical approval was obtained. All patients had a standard CE including 68/66 tender/swollen joint count. Grayscale (GS) and power doppler (PD) US of a standard set of 44 joints was performed using a GE logiq-P9 machine utilising 6-15-MHz and 8-18-MHz linear transducers. GS and PD were scored on a 0-3 semiquantitative scale for each joint. The presence of US active joints was defined as a GS-score ≥2 and/or PD-score ≥1. Results 78 patients were enrolled; 46/78 were female with a median age = 61 years (range 41-80). Median duration of PsA disease = 31.5 years (range 41-80), 40/78 were on bDMARDs and 27/78 on csDMARDs. The median TJC = 2 (range of 0-6) and mean CRP = 3.2 (SD 3.5). The most common sites for subclinical synovitis were wrists, knees, and metatarsophalangeal joints (see Table 1). 36 patients (46.2%) achieved a clinical state of minimal disease activity (MDA). 11 patients in MDA (30.5%) had a PD-score of > 1, suggesting they did not achieve minimal ultrasound disease activity (MUDA). Conclusion These data demonstrate that a proportion of established PsA patients deemed to have MDA actually have sonographic evidence of active disease. A previous study showed that PD-synovitis in PsA patients in clinical remission was a strong predictor of disease flare. It is unclear if subclinical synovitis in PsA is linked to radiographic progression. Combining CE and sonographic evaluation is an attractive approach to identifying subclinical disease. However, a validated ultrasound composite index, which includes the key joint areas frequently affected in PsA, is needed. Disclosure S. Sundanum: None. H. Darcy: None. P. Gallagher: None. F. Young: None. L. O'Neill: None. D. Veale: None.