Background Ultrasound (US) is known to be more sensitive than clinical examination in detecting synovitis in psoriatic arthritis (PsA). However, some studies found disparity between the US and clinical findings
Objectives To assess the prevalence of synovial involvement in early PsA using clinical and sonographic assessments.
Methods A total of 49 subjects with early PsA (CASPAR criteria) recruited in the Leeds Spondyloarthropathy Register for Research and Observation (SpARRO) study, a prospective longitudinal observational cohort, was assessed. The mean disease duration is 1.6 ±0.5 years; F:M ratio is 1.3; median SJC76 is 2 (1–2), median TJC78 is 6 (3–17); 90% of subjects had current skin psoriasis. Baseline US scan was performed on 1274 joints including bilateral wrists, MCP2–3, PIP2–3, elbows, knees, ankles & MTP 1–5. Grey Scale (GS) and Power Doppler (PD) were scored on a 0–3 semi-quantitative scale for each joint. Joints were considered clinically active if tender or swollen, and sonographically active if GS≥2 and/or PD≥1. We compared US active (yes/no) against tender (yes/no) and swollen (yes/no). The majority of the patients (88%) were DMARD naive
Results US identified a higher proportion of subclinical synovitis among swollen rather than tender joints in subjects with early PsA. The agreement between clinical examination (tender & swollen) and US findings was high (73 & 87%) respectively. The most common sites for subclinical synovitis were MTP joints. In contrast, wrist tenderness and MTP2 swelling were the highest overestimated joints among the physical examination.
Conclusions The prevalence of subclinical synovitis is high in early PsA. Joint swelling is more likely to correlate with PD or GS in PsA when compared to joint tenderness. As opposed to RA, where clinical tenderness correlates with subclinical synovitis, the tender joint count may not be a reliable clinical measure to assess synovitis in PsA. Possible reasons for the over-estimation of TJC in clinical examination may be the concomitant occurrence of fibromyalgia. Larger studies are needed to confirm our results.
Disclosure of Interest None declared