Low prevalence of subclinical synovitis in patients with juvenile idiopathic arthritis (JIA) in long-term clinical remission on medication

Subclinical synovitis is highly prevalent in patients with JIA in clinical remission (CR) with a short duration. The objective was to evaluate its prevalence by ultrasound (US) in patients with JIA in long CR during a one-year follow-up. In this prospective and longitudinal study, we included 76 patients with JIA according to ILAR with CR by the Wallace modified criteria and JADAS27 and compared them with 22 patients with active disease. Clinical and demographic characteristics were recorded. US evaluation was by 10-joint count. Differences in US evaluations were analyzed by the Mann–Whitney U test. There were no differences among the two group with regard to disease duration at enrollment, and age (p = 0.540 and p = 0.080, respectively), but JADAS 27, CHAQ, and acute phase reactants were significantly higher (p < 0.001) in the clinically active group. The prevalence of subclinical synovitis at baseline and the end of the study in the CR group was 18.4% and 11.8%, respectively, while it was 100% and 40.9% in the active disease group. Subclinical synovitis at baseline was significantly more prevalent in the clinically active group (elbow, p = 0.01; wrist, p = 0.001; MCP 2, p = 0.001; knee, p = 0.001 and ankle p = 0.001; and PD only in the ankle, p = 0.002). The concordance of inter-reader reliability in all evaluated joints was excellent (p = 0.001). Although the prevalence of subclinical synovitis is low in patients with JIA with long-term clinical remission on medication, a percentage of patients continue to have subclinical involvement that could predict the risk of relapse and structural damage.