>CME/CNE ARTICLE: Severity Grading in Multiple Sclerosis: A Proposal

Abstract

Currently used classification schemes for multiple sclerosis (MS) have not taken into account disease severity, instead focusing on disease phenotype (ie, relapsing vs. progressive). In this article, we argue that disease severity adds a crucial dimension to the clinical picture and may help guide treatment decisions. We outline a practical, easy-to-implement, and comprehensive scheme for severity grading in MS put forward by our mentor, Professor Joseph Herbert. We believe that severity grading may help to better prognosticate individual disease course, formulate and test rational treatment algorithms, and enhance research efforts in MS.

Figure 1.

Illustration of the concept of the Multiple Sclerosis Severity Score, a disease duration–adjusted disability score Each color represents an Expanded Disability Status Scale (EDSS) score. This hypothetical reference population of 50 patients with disease duration of x years has been lined up in order of increasing EDSS scores: two patients have EDSS scores of 0 (dark blue), ranked 1 and 2; seven have EDSS scores of 1 (blue), ranked 3 to 9; 12 have EDSS scores of 2 (cyan), ranked 10 to 21; ten have EDSS scores of 3 (turquoise), ranked 22 to 31; nine have EDSS scores of 4 (green), ranked 32 to 40; four have EDSS scores of 5 (yellow), ranked 41 to 44; two have EDSS scores of 6 (orange), ranked 45 and 46; two have EDSS scores of 7 (red), ranked 47 and 48; one has an EDSS score of 8 (purple), ranked 49; and one has an EDSS score of 9 (indigo), ranked 50. Severity score is the normalized mean rank, which is computed by taking the mean rank for each score divided by the total cohort count +1 and then multiplied by 10. For example, in the reference population, the severity score for the EDSS of 4 for patients with disease duration of 5 years would be 10×mean(32,33,34,35,36,37,38,39,40)/50+1 = 360/51 = 7.1.

Figure 2.

Herbert's six severity grades: H1 to H6 Herbert's severity grading divides patients with multiple sclerosis into six approximately equipopulated tiers of disability based on their Multiple Sclerosis Severity Score.