The association between ethnicity, socioeconomic position and outcomes following initiation of methotrexate in juvenile idiopathic arthritis.

Objectives: This analysis investigates changes in disease activity and treatment persistence following initiation of methotrexate in children and young people with juvenile idiopathic arthritis (JIA), by ethnic group and socioeconomic position. Methods: Patients registered in the UK JIA Biologics Register starting methotrexate were included. Outcomes included a change in disease activity between treatment commencement and 6 months. Adjusted multivariable linear regression was used to assess the association between ethnicity or socioeconomic position. Treatment persistence was analysed using Kaplan-Meier estimates. Cox proportional hazards models were used to compare drug persistence between groups. Results: A total of 993 patients were included; 69% women, 88% White ethnic group (2% Mixed, 8% Asian, and 2% Black), and 24% in the most deprived socioeconomic group. Disease activity improved after 6 months for most children. There was no evidence that improvement differed by ethnicity or socioeconomic position.The proportion of patients remaining on methotrexate at 12 months varied by ethnic group (61% of children with White ethnicity, 64% Asian, 65% Black, and 67% of children with Mixed ethnicity). The likelihood of stopping methotrexate over the 12-month period was similar between ethnicities and socioeconomic groups. Conclusions: Improvements in disease activity in the first 6 months following initiation of methotrexate in children and young people with JIA are similar between ethnic groups and independent of socioeconomic position. Although small sample sizes limit robust conclusions, further research to understand whether differences are seen following initiation of other therapies for JIA and the drivers of these differences is warranted.