Despite the high level of effectiveness of natalizumab (NTZ) in the treatment of patients with multiple sclerosis (MS), concerns about its high direct cost and its safety have restricted its use. Our aim was to identify and quantify the clinical factors that predict an optimal response to NTZ. Patients with MS undergoing treatment with NTZ for at least 12 months were classified as optimal responders if, during treatment, they sustained a reduction in their Kurtzke Expanded Disability Status Scale (EDSS) score of 1 point or more or experienced a reduction in annualised relapse rate (ARR) of more than 1. The remaining patients were classified as suboptimal responders and non-responders. Our subject pool included 48 patients. The variables associated with optimal response included: ARR in the previous year of at least 2, an age at first administration of 37.5 years or less, a baseline EDSS score of 4.5 points or less, a disease duration of 9.5 years or less and, in patients with secondary-progressive MS, a progressive-phase duration of 4.5 years or less. The characteristics of the disease at its onset did not affect responsiveness, indicating that patients with highly active disease and low disability are the ideal candidates for NTZ treatment, regardless of previous clinical characteristics.
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