Kappos L, Wolinsky JS, Giovannoni G, et al. - Given that accumulation of disability in multiple sclerosis can occur as relapse-associated worsening (RAW) or steady progression independent of relapse activity (PIRA), with PIRA regarded as a characteristic of primary and secondary progressive multiple sclerosis, researchers examined the contributions of RAW vs relapse-independent progression to overall confirmed disability accumulation and evaluated respective baseline prognostic factors and outcomes of 2 treatments. In the pooled OPERA I and II population (1,656 of 2,096 eligible candidates), baseline demographics and disease features were comparable for patients randomized to interferon β-1a vs ocrelizumab (mean [SD] age, 37.2 [9.2] vs 37.1 [9.2] years; 552 [66.6%] vs 541 women [65.4%]). Findings suggested no association of most disability accumulation in RMS with overt relapses. This shows an underlying progression in this typical RMS population and questions the current clinical distinction of relapsing and progressive forms of multiple sclerosis. Ocrelizumab was stronger than interferon β-1a in both RAW and PIRA prevention.