Agreement Between the Harmonized and the Self-Explanatory Versions of the Revised ALS Functional Rating Scale in a Clinical Setting.

INTRODUCTION/AIMS: The harmonized version of the ALS Functional Rating Scale - Revised (ALSFRS-R) is typically administered according to standard operating procedures (SOPs) to ensure procedural consistency. In contrast, obtaining the self-explanatory (SE) version of the ALSFRS-R does not include the use of SOPs. The aim of this study was to examine the level of agreement between the harmonized and the SE version of the ALSFRS-R in a cohort of ALS patients. METHODS: In a prospective study, the harmonized ALSFRS-R was assessed in 107 ALS patients. In parallel, all patients independently completed the ALSFRS-R-SE, either on a printed form (n = 36) or remotely via the ALS App (n = 71). Agreement between methods was investigated using Spearman's correlation, Lin's concordance correlation coefficient (CCC), Deming regression, Bland-Altman plots and item-level statistics including Kendall's tau-b and the Stuart-Maxwell test. RESULTS: Total scores from ALSFRS-R and ALSFRS-R-SE showed high correlation (ρ = 0.91-0.95) and concordance (CCC > 0.9). Deming regression (intercept≈0; slope≈1) and Bland-Altman analysis (95% of values within limits of agreement [LoA]) revealed no systematic bias. Item-level agreement was high (76.6% on average), with some variability in items such as handwriting, walking, and dyspnea. ALS progression rates were consistent (differences ≤ 0.02). ALSFRS-R-SE remained robust across remote digital and paper-based assessments. DISCUSSION: The strong agreement between the harmonized and self-explanatory versions of the ALSFRS-R supports their interchangeable use. The SE format may facilitate remote digital assessment and reduce complexity of ALSFRS-R assessment in research and clinical practice. Further studies are warranted to validate the ALSFRS-R-SE across larger cohorts, multiple languages, and diverse rater groups.