The role of musculoskeletal ultrasound in predicting the response to JAK inhibitors. results from a monocentric cohort

Objectives: In this longitudinal study, we assessed the role of musculoskeletal ultrasound (US) in predicting the efficacy of JAK inhibitors (JAKi) in rheumatoid arthritis (RA) patients. Methods: We enrolled RA patients starting baricitinib or tofacitinib. All patients were evaluated at baseline and after 4, 12, 24, 48 weeks. Disease activity was calculated by Disease Activity Score 28 (DAS28CRP); US examination in 22 joints (I-V MCPs and PIPs, wrists) aimed at evaluating inflammatory features (synovial effusion and hypertrophy, power Doppler-PD), scored through a semi-quantitative scale (0-3). The total US (0-198) and PD (0-66) scores were calculated. We scanned bilateral flexor (I-V fingers of hands) and extensor compartments (1-6) tendons: tenosynovitis was scored as absent/present (0/1), resulting in a total score ranging from 0 to 22. Results: We studied 102 patients (M/F 15/87; median age 59.2 years, IQR 17.75; median disease duration 144 months, IQR 126), 61 treated with baricitinib and 41 with tofacitinib. At baseline, the median total US score was 18 (IQR 19) and the median PD score 2 (4). We observed a significant reduction in both total and PD US scores at all time-points (p<0.0001). At baseline, 75.4% of patients showed tenosynovitis involving at least one tendon, with a median score of 2 (IQR 3.5) significantly decreasing after 24 weeks (p=0.02). At multivariate analysis, PD and tenosynovitis score significantly correlated with changes in DAS28CRP. Conclusions: The present study confirmed the early efficacy of JAKi in RA patients by using US evaluation. Furthermore, we found that power Doppler and tenosynovitis scores could play a predictive role in response to treatment.