Clinical instrument to retrospectively capture levels of EDSS

Background: The Expanded Disability Status Scale (EDSS), a common outcome measure in Multiple Sclerosis (MS), is obtained prospectively through a direct standardized evaluation. The objective of this study is to develop and validate an algorithm to derive EDSS scores from previous neurological clinical documentation. Methods: The algorithm utilizes data from the history, review of systems, and physical exam. EDSS scores formally obtained from research patients were compared to captured EDSS (c-EDSS) scores. To test inter-rater reliability, a second investigator captured scores from a subset of patients. Agreement between formal and c-EDSS scores was assessed using a weighted kappa. Clinical concordance was defined as a difference of one-step in EDSS (0.5) and functional system (1.0) scores. Results: Clinical documentation from 92 patients (EDSS range 0.0-8.5) was assessed. Substantial agreement between the c-EDSS and formal EDSS (kappa 0.80; 95% CI 0.74-0.86) was observed. The mean difference between scores was 0.16. The clinical concordance was 78%. Near-perfect agreement was found between the two raters (kappa 0.89; 95% CI 0.84-0.95). The mean inter-rater difference in c-EDSS was 0.23. Conclusions: This algorithm reliably captures EDSS scores retrospectively with substantial correlation with formal EDSS and high inter-rater agreement. This algorithm may have practical implications in clinic, MS research and clinical trials.