Predicting beta-interferon failure in relapsing-remitting multiple sclerosis

Proposed beta-interferon (IFN beta) treatment failure criteria for patients with relapsing-remitting multiple sclerosis (RRMS) have not been validated in clinical practice. This study aimed to establish (a) whether IFN beta attenuated accumulation of fixed disability in comparison to a cohort of matched historical control subjects from the Sylvia Lawry centre for MS research, and (b) whether relapse based treatment failure criteria or clinical and demographic variables had predictive value for the accumulation of fixed disability. Of the 175 IFN beta-treated RRMS patients, 60 (34%) developed accumulation of fixed disability over a median of five,years follow-up, which was significantly less than the rate of accumulation of fixed disability in the control group (P < 0.0001). Any relapse in the treatment period predicted accumulation of fixed disability, with a sensitivity of 80% and specificity of 43%; patients totally relapse free were less likely to develop accumulation of fixed disability (P < 0.002). Multivariate analysis confirmed that a greater risk of accumulation of fixed disability was conferred by a higher Expanded Disability Status Scale (EDSS) score starting IFN beta (P = 0.02), and by failure of IFN beta to completely suppress relapses (P = 0.004). In conclusion, IFN beta therapy reduced the accumulation of fixed disability in a cohort of RRMS patients, followed for a median of five years. Higher baseline EDSS and failure of complete relapse suppression were associated with a significantly greater likelihood of accumulation of fixed disability.