Abstract
Objective
To evaluate the relationship between clinical examination/ultrasound (US) synovitis in DMARD-naïve early PsA.
Methods
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 or PD ≥ 1 was calculated by prevalence-adjusted and bias-adjusted kappa (PABAK). To derive probabilities of GS ≥ 2/PD ≥ 1, mixed-effects logistic regression modelled odds of US synovitis in TJ/SJ were conducted.
Results
In 155 patients, 5,616 joints underwent clinical/US examination. Of these joints, 1039/5616 (18.5%) were tender, 550/5616 (9.8%) were swollen, 1144/5616 (20.4%) had GS ≥ 2, and 292/5616 (5.2%) had PD ≥ 1. GS ≥ 2 was most prevalent in concomitantly tender and swollen joints [205/462 (44%)] followed by swollen non-tender joints [32/88 (36.4%)], tender non-swollen joints [148/577 (25.7%)], and non-tender non-swollen joints (subclinical synovitis) [759/4489 (16.9%)]. Agreement between SJ/PD ≥ 1 was high at the individual joint level (82.6%-96.3%, PABAK 0.65–0.93) and for total joints combined (89.9%, PABAK 0.80). SJ/GS ≥ 2 agreement was greater than between TJ/GS ≥ 2 [73.5%-92.6% vs 51.0%-87.4% (PABAK 0.47–0.85 vs PABAK 0.35–0.75) respectively]. Swelling was independently associated with higher odds of GS ≥ 2 [odds ratio (OR) (95% CI); 4.37 (2.62, 7.29); p < 0.001] but not tenderness [OR = 1.33 (0.87, 2.06); p = 0.192]. Swelling [OR = 8.78 (3.92, 19.66); p < 0.001] or tenderness [OR = 3.38 (1.53, 7.50); p = 0.003] were independently associated with higher odds of PD ≥ 1.
Conclusion
Synovitis (GS ≥ 2 and/or PD ≥ 1) was more likely in swollen joints than tender joints in DMARD-naïve, early PsA. Agreement indicated swollen joints were the better proxy for synovitis, adding to greater understanding between clinical/US assessments.