Effect of a self-management intervention for newly diagnosed inflammatory arthritis: study protocol for a randomized controlled trial.

backgroundPatients newly diagnosed with inflammatory arthritis (IA) often face substantial physical, psychological, and social challenges despite advances in pharmacological management.

objectiveTo investigate the efficacy of the "Newly diagnosed with Inflammatory arthritis-a Self-MAnagement intervention" (NISMA) and usual care, compared to usual care alone (control group), in adults with newly diagnosed IA.

methodsThis pragmatic, multicenter randomized controlled trial (RCT) will enroll 130 adults with rheumatoid arthritis (RA), psoriatic arthritis (PsA), or axial spondyloarthritis (axSpA) recruited consecutively from three Danish hospitals and randomized 1:1 to NISMA plus usual care or usual care alone. The control group receives usual care, which consists of planned consultations with a rheumatologist and access to nurses. NISMA comprises three mandatory individual nurse-led sessions with two optional multidisciplinary group sessions delivered over 12 months. Assessments occur at baseline, 12 months (primary), and 24 months (extension). The primary outcome is the Health Education Impact Questionnaire (heiQ) "skill and technique acquisition" domain. STATISTICAL ANALYSIS: Analyses follow the intention-to-treat principle. For the primary analysis, analysis of covariance (ANCOVA) adjusted for baseline, center, and diagnosis will estimate between-group differences with two-sided 95% CIs. Model assumptions (normality, homoscedasticity) will be checked (Q-Q plots, residual diagnostics). If violated, pre-specified alternatives (e.g., transformation, rank-based ANCOVA, or nonparametric tests) will be used. Missing data will be addressed using multiple imputation. Key secondary endpoints will be assessed in a pre-specified hierarchical (gatekeeping) order; any post hoc analyses will be exploratory. Extension analyses at 24 months will use linear mixed-effects models. DISCUSSION: This randomized controlled trial will provide essential insights about the efficacy of a targeted self-management intervention for newly diagnosed patients with inflammatory arthritis. If successful, the NISMA intervention could significantly enhance non-pharmacological management, providing a comprehensive approach to addressing both physical and psychological needs in caring for patients newly diagnosed with IA. TRIAL REGISTRATION {2B}: ClinicalTrials.gov, nr.: NCT06533423. Registered on December 19, 2024. PROTOCOL VERSION {3}: 22.09.2025. Version 2.