Disease steps in multiple sclerosis: a simple approach to evaluate disease progression

Current clinical scales in multiple sclerosis (MS) are often complicated to administer, suffer from interrater variability and lack of uniform representation across grades, and are insensitive to progression at certain stages. Furthermore, they are not easily applied by neurologists and do not clearly differentiate among functional stages of MS. For these reasons, we developed Disease Steps to assess disability in MS. A total of 1,323 patients were classified using both Disease Steps and the Expanded Disability Status Scale (EDSS) for a total of 2,755 assessments. The Disease Steps scale consists of 0 = Normal; 1 = Mild disability, mild symptoms or signs; 2 = Moderate disability, visible abnormality of gait; 3 = Early cane, intermittent use of cane; 4 = Late cane, cane-dependent; 5 = Bilateral support; 6 = Confined to wheelchair; and U = Unclassifiable. Results demonstrate that raters could simply and quickly categorize patients using Disease Steps. Patients were uniformly distributed with Disease Steps, whereas a bimodal distribution occurred with the EDSS. On the EDSS, 40.3% of patients scored between 1.0 and 3.5 and 36.0% scored from 6.0 to 6.5, with only 6.9% of patients scoring between 4.0 and 5.5. For 60 patients seen by two neurologists, concordance between raters was excellent for Disease Steps (kappa = 0.8) but only moderate for the EDSS (kappa = 0.54). As a simple and reproducible measure of different functional steps of MS, Disease Steps can be used as a guide in therapeutic decision-making, following response to therapy, and in assessing disease progression.