• cohort study;
  • interferon beta;
  • propensity score;
  • relapsing-remitting multiple sclerosis;
  • treatment effectiveness


Rationale, aims and objectives  Randomized clinical trials (RCTs) have provided evidence for the efficacy of interferon beta (IFNβ) in the treatment of relapsing-remitting multiple sclerosis (RRMS). The aim of this study was to evaluate the effectiveness of IFNβ treatment in clinical practice.

Methods  This was a national, multicentre, observational study of patients with confirmed RRMS. Demographic, clinical and therapeutic data were retrospectively collected for each patient enrolled in the study.

Results  The study cohort consisted of 427 patients exposed to and 245 never exposed to IFNβ treatment during the study period (for a total 2297 patient-years of follow-up). Among the exposed patients, 215 were initially untreated and then began IFNβ later in the follow-up period; 137 of these patients were exposed to IFNβ for more than 2 years. In these patients, IFNβ treatment reduced the mean relapse rate by 24.2%[95% confidence interval (CI): 5.8–42.5%]. For 640 of the 672 patients enrolled in the study, it was possible to calculate the area under the disability/time curve compared to that present at baseline. A total of 117 (18.3%) patients displayed disability progression. Adjustment of the disability progression rates for potential confounders and/or for propensity scores by Poisson regression model resulted in relative risks for patients exposed to IFNβ treatment compared to those never exposed to IFNβ of 0.87 (95% CI: 0.56–1.34) after an exposure of ≤ 2 years, and of 0.35 (95% CI: 0.21–0.60) after an exposure of > 2 years.

Conclusions  These findings suggest that the evidence from RCTs on the treatment of RRMS with IFNβ has been effectively translated into routine clinical practice.