Modified EDSS for Use in Multiple Sclerosis Clinical Practice

Background:   The Expanded Disability Status Scale (EDSS) is the standard research measure of disability in multiple sclerosis (MS). Limitations for clinical use include time required for administration, scoring complexity, and technique redundancy. If simplified, the EDSS would provide a standardized numerical rating to monitor disease progression and treatment response in the clinical setting.

Objectives:   To develop a modified version of the EDSS (mEDSS) for clinical monitoring and compare this modified version to the full EDSS.

Methods: The existing EDSS was modified in several ways, via consensus among 3 MS specialists, to create the mEDSS: exam maneuvers which do not impact function were eliminated (e.g. reflexes), redundant maneuvers were consolidated (e.g. proprioception), and scoring of functional systems was simplified. The mEDSS was designed to reflect a more concise EDSS that utilizes exam techniques important for clinical monitoring. Existing data from the CombiRx trial was used to ensure standardized ascertainment of the EDSS; from these data, we derived the mEDSS. The mEDSS and EDSS, as well as each functional system (FS), were compared using Spearman’s rank correlation coefficients and Bland-Altman plots. Discrepancies within each FS between the EDSS and mEDSS were delineated within a subset with physical charts available for review.

Results: The mEDSS at the baseline CombiRx trial visit (n=1005) was derived and EDSS values ranged between 0 and 6. The mEDSS had strong correlation with the EDSS, both overall (Spearman’s rho = 0.88, p<0.0001) and for each functional system (Spearman’s rho between 0.64 and 0.97, p-values<0.001). Bland-Altman plots to examine agreement will be presented. The algorithm to derive mEDSS from the EDSS information was validated and discrepancies in functional systems were identified in the chart review. Reasons for discordant scores will be delineated.

Conclusions: The mEDSS was strongly correlated with the full EDSS and can therefore provide a useful measure of disability in clinical practice. The development and validation of an automated statistical algorithm enabled us to compare the mEDSS and EDSS in a large population to examine differences in scoring. Longitudinal assessment of the mEDSS for stability and relapse sensitivity is in progress. Future work will examine the practicality and interrater reliability of the mEDSS.