A comparison of two neurologic scoring instruments for multiple sclerosis

We examined the degree of association between two neurologic impairment scales, the Extended Disability Status Scale (EDSS) and the Scripps Neurologic Rating Scale (SNRS), with data from a randomized, double-blind, placebo-controlled clinical trial assessing the safety and efficacy of cladribine as treatment for chronic progressive multiple sclerosis (MS). We found that the EDSS and SNRS were not strongly correlated within individual patients, contrary to expectation; moreover, in 9 of the 48 evaluable patients, the directions of their changes from baseline values were not mutually consistent. The scales were differentially sensitive to clinical changes over time, with the EDSS indicating a more abrupt, and the SNRS a more gradual, change in the clinical course of disease. The validity of different impairment scales, and their sensitivity to detect clinical changes, should be formally assessed in future clinical trials using these scales as outcome measures.