Interferon beta-1a decreased the risk for conversion to clinically definite multiple sclerosis.

P a t i e n t s 308 patients (mean age 28 y, 64% women) who had presented with a first neurologic episode (unifocal or multifocal involvement of the central nervous system) suggesting MS in the previous 3 months, with ≥ 1 abnormality evident during the neurologic examination and a positive magnetic resonance imaging (MRI) scan result. Exclusion criteria included immunosuppressive or immunomodulatory treatment, participation in any experimental procedure during the year before the study, and serious comorbid systemic illnesses or psychiatric disorders.