Rationale, aims and objectives: Randomized clinical trials (RCTs) have provided evidence for the efficacy of interferon beta (IFNbeta) in the treatment of relapsing-remitting multiple sclerosis (RRMS). The aim of this study was to evaluate the effectiveness of IFNbeta 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 IFNbeta 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 IFNbeta later in the follow-up period; 137 of these patients were exposed to IFNbeta for more than 2 years. In these patients, IFNbeta 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 IFNbeta treatment compared to those never exposed to IFNbeta of 0.87 (95% CI: 0.56-1.34) after an exposure of < or = 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 IFNbeta has been effectively translated into routine clinical practice.