Objective: To compare the effectiveness of tumor necrosis factor inhibitors (TNFi) ± comedication and methotrexate (MTX) monotherapy between patients with adult juvenile idiopathic arthritis (JIA) and patients with rheumatoid arthritis (RA).
Methods: Adult patients with JIA and RA were identified from the Norwegian Antirheumatic Drug Register (NOR-DMARD) register. Disease activity measurements at baseline, 3, 6, and 12 months were compared between patients with JIA and RA starting (1) TNFi and (2) MTX monotherapy, using age- and gender-weighted analyses. We calculated differences between JIA and RA in mean changes in Disease Activity Score in 28 joints (DAS28), Clinical Disease Activity Index (CDAI), and Simplified Disease Activity Index (SDAI), among other disease activity measures. DAS28, CDAI, SDAI, and American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) remission rates at 3, 6, and 12 months, as well as 6- and 12-month Lund Efficacy Index (LUNDEX)-corrected rates, were calculated.
Results: We identified 478 patients with JIA (TNFi/MTX monotherapy, n = 358/120) and 4637 patients with RA (TNFi/MTX monotherapy, n = 2292/2345). Patients with JIA had lower baseline disease activity compared to patients with RA across treatment groups. After baseline disease activity adjustment, there were no significant differences in disease activity change from baseline to 3, 6, and 12-months of follow-up between patients with JIA and RA for either treatment group. Twelve-month remission rates were similar between groups based on DAS28 (TNFi: JIA 55.2%, RA 49.5%; MTX monotherapy: JIA 45.3%, RA 41.2%) and ACR/EULAR remission criteria (TNFi: JIA 20.4%, RA 20%; MTX monotherapy: JIA 17%, RA 12.7%). Median drug survival (yrs) was similar for JIA and RA in both treatment groups (TNFi: JIA 1.2, RA 1.4; MTX monotherapy: JIA 1.3, RA 1.6).
Conclusion: TNFi and MTX monotherapy are effective in adult JIA, with similar effectiveness to that shown in RA.