A comparative study of fatigue and processing speed in patients with multiple sclerosis treated with natalizumab or rituximab

Background: Fatigue is the most debilitating symptom in patients with multiple sclerosis (MS). Natalizumab and rituximab are the most used MS disease modifying therapies in Sweden, but comparative data on the effect on fatigue is sparse. Objective: Primary objective was to compare fatigue levels between patients on natalizumab and rituximab. As secondary objective, we assessed processing speed, an attention domain quality, between treatment groups. Method: In this Swedish multicentre cross-sectional study, patients with relapsing-remitting MS and >24 months treatment duration were identified in the Swedish MS-registry. Fatigue was assessed using the Fatigue Scale for Motor and Cognitive functions (FSMC) and processing speed using Symbol Digit Modalities Test (SDMT). Results: 128 patients were enrolled (natalizumab: 56, rituximab: 72). No significant differences in FSMC were found when adjusting for potential confounders (p = 0.936), with age having the biggest impact, correlating with increased fatigue. Individuals on natalizumab performed significantly better on SDMT at cross-section (natalizumab 64.7, rituximab 56.2; p = 0.003), with an improvement from treatment initiation, compared to rituximab (change: natalizumab 8.9, rituximab −1.0; p = 0.002). Conclusion: We found no difference in fatigue levels between natalizumab and rituximab cohorts. Patients treated with natalizumab showed significantly better results on SDMT than patients on rituximab.