The challenges of measuring disability accumulation in relapsing–remitting multiple sclerosis: evidence from interferon beta treatments

Irreversible disability is the critical long-term consequence of multiple sclerosis (MS). While there are well-established measures for disability in MS, they have limitations that may affect our perception of disease progression either due to the empirical nature of some assessments or the lack of validation with long-term outcomes. Measuring effects on disability accumulation in relapsing-remitting MS is also difficult in clinical trial situations because of the protracted evolution of the disease and the ethical and practical implications of long-term placebo-controlled trials, which may have implications for clinicians considering treatment options. Despite these issues, interferon-beta therapies have decades of follow-up data, with which it is possible to evaluate prognostic factors for the accumulation of disability in relapsing-remitting MS.