Prevalence of Anti-infliximab Antibodies and Their Associated Co-factors in Children with Refractory Arthritis and/or Uveitis: A Retrospective Longitudinal Cohort Study.

OBJECTIVE: Infliximab (IFX) is a monoclonal tumor necrosis factor-α-inhibiting antibody used in children with refractory arthritis and uveitis. Immunogenicity is associated with a lack of clinical response and infusion reactions in adults; data on immunogenicity in children treated with IFX for rheumatic diseases are scarce. We aimed to describe the prevalence of anti-IFX antibodies and determine co-factors associated with anti-IFX antibodies in children with inflammatory rheumatic and ocular diseases.

METHODS: Consecutive children treated between August 2009 and August 2012 with IFX at our department were included. Blood samples were collected every 6 months before IFX infusion and tested for anti-IFX antibodies by radioimmunoassay. Patients' charts were retrospectively reviewed for clinical features and analyzed for associations with anti-IFX antibodies.

RESULTS: Anti-IFX antibodies occurred in 14/62 children (23%) and 32/253 blood samples (12.6%) after a mean treatment time of 1084 days (range 73-3498). Infusion reactions occurred in 10/62 (16%) children during the treatment period. With continuation of IFX, anti-IFX antibodies disappeared in 7/14 children. In the bivariate analysis, the occurrence of anti-IFX antibodies was associated with younger age at IFX treatment start (mean age 7.01 vs 9.88 yrs, p = 0.003) and infusion reactions (OR 15.0), while uveitis as treatment indication was protective against development of anti-IFX antibodies (OR 0.17), likely because of higher IFX doses. In the multivariate logistic regression, all 3 covariates remained highly significant.

CONCLUSION: Anti-IFX antibodies occurred commonly at any time during IFX treatment. Anti-IFX antibodies were associated with younger age at IFX start, infusion reactions, and arthritis as treatment indication.