Clinical and Ultrasound Remission in Rheumatoid Arthritis Patients Treated with JAK Inhibitors: A Real-World Study

<b>Background:</b> Janus kinase inhibitors (JAKi) are approved for the treatment of rheumatoid arthritis (RA), aiming to achieve clinical remission. Composite scores such as Disease Activity Score in 28 joints with C-reactive protein (DAS28-CRP) are influenced by subjective factors, and JAKi may impact these dimensions beyond inflammation. Ultrasound provides a sensitive and objective assessment of synovial activity. <b>Objective:</b> To evaluate clinical and ultrasound-defined remission in RA patients treated with JAKi under routine care. <b>Methods:</b> This cross-sectional study included all consecutive patients treated with baricitinib, filgotinib, tofacitinib, or upadacitinib between 1 November 2022 and 30 April 2023. Clinical remission was defined as DAS28-CRP and ultrasound remission as absence of power Doppler (PD) signal across a standardized 32-joint evaluation. <b>Results:</b> We include 78 patients with established RA; 87.2% were female, with mean age of 59.5 ± 10.8 years and disease duration of 10.6 ± 8.0 years. Most were seropositive for RF and/or ACPA (74.4%), and comorbidities were highly prevalent (93.6%). Clinical remission was observed in 42.3% and ultrasound remission in 56.4%, with no statistically significant differences between JAKi groups. Among 50 patients meeting remission by either definition, 30 (60%) fulfilled both criteria, 11 (22%) had ultrasound remission only, and 9 (18%) met clinical remission without sonographic confirmation. Discordant cases were often associated with osteoarthritis, fibromyalgia, mood disorders, and elevated inflammatory markers. <b>Conclusions:</b> JAKi were effective in achieving remission in many RA patients. Ultrasound revealed residual synovitis despite clinial remission and, conversely, silent remission in cases not meeting DAS28-CRP criterion, reinforcing its value for accurate monitoring and personalized therapeutic decisions. No meaningful clinical or ultrasonographic differences were observed between the various JAK inhibitors, indicating comparable perfomance across agents in routine practice.