Between-hospital variation in discontinuation of treatment with dimethyl fumarate in multiple sclerosis

BACKGROUND: In multiple sclerosis (MS), switching disease modifying treatment is associated with higher relapse rate, healthcare expenses, disease burden, and lower quality of life. We compared drug discontinuation rates of dimethyl fumarate (DMF) between hospitals in Denmark and Norway. METHOD: Data from national MS registries were analyzed, adjusting for sex, age, disease duration, Expanded Disability Status Scale, and baseline relapses. Between-hospital variation was assessed using median hazard ratios (MHR). RESULTS: 3368 patients with relapsing-remitting MS started DMF at all clinics in Denmark (n = 14) and at a subset of clinics in Norway (n = 6). A median of 44% discontinued DMF. Predictors for discontinuation were female sex, younger age, higher EDSS and number of relapses at baseline. There was a significant difference in the risk of discontinuation between hospitals. The MHR for discontinuation because of treatment failure attributed to treating hospital was 1.51(SE 0.120, p < 0.001) in Norway and 1.34 (SE 0.055, p < 0.001) in Denmark. CONCLUSION: Discontinuation rates of DMF in MS varies between hospitals, independent of patient characteristics.