Swelling and not tenderness of joints better predicts synovitis in psoriatic arthritis

UK: Swollen joints are the better proxy for ultrasound (US) synovitis as compared to tender joints in DMARD-naive early psoriatic arthritis (PsA) patients, states an article published in Rheumatology Advances in Practice.

In Psoriatic Arthritis (PsA), the initial diagnosis and assessment are dependent upon the identification of swollen and tender joints by clinical examination. The tender/swollen joint counts (TJC/SJC) are also key components in composite outcome measures of PsA. Synovitis in PsA may manifest as swelling of joints on clinical examination but PsA patients often report joint pain and may have tender joints without swelling, which may relate to other pathologies.

Ultrasound (US) is increasingly used in PsA diagnosis and management to identify joint synovitis, and peri-tendon/tendon/entheseal inflammation, owing to its superior sensitivity over the clinical examination. Understanding the relationship between clinical joint tenderness/swelling and US synovitis remains crucial for improving the early identification of disease, decision-making, and therapeutic intervention.

Sayam R, University of Leeds, UK, and colleagues conducted a study to determine the association between joint clinical examination findings and US synovitis in early PsA.

Researchers enrolled 155 consecutive disease-modifying antirheumatic drugs (DMARD)-naïve PsA patients for the prospective cohort study. Eligible patients underwent matched clinical/US 44-joint assessment for tender and/or swollen joints (TJ/SJ) and US synovitis [grey scale (GS) ≥ 2 or power Doppler (PD) ≥ 1]. Statistical agreement between TJ/SJ, GS ≥ 2, and PD ≥ 1 was calculated by prevalence-adjusted and bias-adjusted κ (PABAK). To derive probabilities of GS ≥ 2/PD ≥ 1, mixed-effects logistic regression-modeled odds of US synovitis in TJ/SJ were conducted.

Key findings of the study,

• Of the total 5616 joints examined,18.5% were tender, 9.8% were swollen, 20.4% had GS ≥ 2, and 5.2% had PD ≥ 1.

• GS ≥ 2 was most prevalent in concomitantly tender and swollen joints (44%), followed by swollen non-tender joints (36.4%), tender non-swollen joints (25.7%), and non-tender non-swollen joints (subclinical synovitis) (16.9%).

• Agreement between SJ/PD ≥ 1 was high at the individual joint level (PABAK 0.65–0.93) and for total joints combined (PABAK 0.80).

• SJ/GS ≥ 2 agreement was greater than between TJ/GS ≥ 2.

• The swelling was independently associated with higher odds of GS ≥ 2 but not tenderness.

• Swelling or tenderness was independently associated with higher odds of PD ≥ 1.

The authors conclude that synovitis (GS ≥ 2 and/or PD ≥ 1) was more likely in swollen joints than in tender joints in DMARD-naïve, early PsA. The study findings might help to improve the management of early PsA by adding to the understanding of the relation between clinical examination and underlying pathologies in US imaging.

Reference:

Sayam R Dubash, Oras A Alabas, Xabier Michelena, Leticia Garcia-Montoya, et al. Ultrasound shows swollen joints are the better proxy for synovitis than tender joints in DMARD-naïve early psoriatic arthritis, Rheumatology Advances in Practice, Volume 5, Issue 3, 2021, rkab086, https://doi.org/10.1093/rap/rkab086