Predicting achievement of the treatment targets at 6 months from 3-month response levels in rheumatoid arthritis: data from real-life follow-up in the NOR-DMARD study

Objective When initiating a new therapy in patients with rheumatoid arthritis (RA), current treatment recommendations suggest escalating therapy in case of poor clinical improvement by 3 months or if the treatment target has not been reached by 6 months. We investigated which disease activity improvement levels at 3 months predicted achievement of the treatment targets at 6 months in a real-life clinical setting. Methods We included 1610 patients with RA enrolled in the NOR-DMARD study between 2000 and 2012. Analyses were performed for the total group of patients and repeated for subgroups stratified by baseline disease activity, disease duration or treatment with methotrexate or a tumour necrosis factor inhibitor. We used a diagnostic test approach to explore the associations between 3-month response and 6-month outcome. Results Not achieving 50% improvement in Simplified Disease Activity Index (SDAI) by 3 months significantly decreased the likelihood of reaching remission at 6 months in all subgroups (negative likelihood ratios (LRs-) 0.15-0.36). Patients with high disease activity when initiating treatment were likely to fail reaching remission if they achieved less than SDAI 70% response by 3 months (LR- 0.25 and negative predictive value 0.98). Achieving a major response (SDAI 85%) at 3 months significantly increased the likelihood of reaching remission at 6 months (LRs+ 6.56). Conclusion Levels of 3-month disease activity improvement can inform clinicians when deciding to continue or adjust ongoing therapy in a treat-to-target strategy aiming for remission or low disease activity within 6 months. The required levels of 3-month improvement varied with baseline disease activity.