Multiple Sclerosis Progressive Courses: A Clinical Cohort Long-Term Disability Progression Study

Objectives: Improving the understanding of multiple sclerosis (MS) mechanism and disability progression over time is essential to assess the value of healthcare interventions. Poor or no data on disability progression are available for progressive courses. This study aims to fill this gap.Methods: An observational cohort study of patients with primary MS (PPMS) and secondary progressive MS (SPMS) was conducted on 2 Italian MS centers disease registries over an observational time of 34 years. Annual transition probabilities among Expanded Disability Status Scale (EDSS) states were estimated using continuous Markov models. A sensitivity analysis was performed in relation to clinical characteristic associated to disability progression.Results: The study cohort included 758 patients (274 PPMS and 434 SPMS) with a median follow-up of 8.2 years. Annual transition probability matrices of SPMS and PPMS reported different annual probabilities to move within EDSS levels. Excluding EDSS associated to relapse events or patient with relapses, the annual probability of staying stable in an EDSS level increased in both disease courses even not significantly.Conclusions: This study provides estimates of annual disability progression as EDSS changes for PPMS and SPMS. These es-timates could be a useful tool for healthcare decision makers and clinicians to properly assess impact of clinical interventions.