Rate of disease progression: a prognostic biomarker in ALS.

Objective: To assess the utility of rate of disease progression (ΔFS) as a prognostic biomarker in amyotrophic laterals sclerosis (ALS).

Methods: A total of 203 patients with ALS were prospectively recruited over a 10-year period. At initial visit, the following variables were collected: demographic details, symptom duration, site of onset, phenotype, riluzole use and Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) scores. The ΔFS score at initial visit was calculated by dividing the ALSFRS-R total score by symptom duration (months). The primary end point was survival. Kaplan-Meier survival curves were used to illustrate the distribution of survival from a specified point, while multiple Cox proportional hazards modelling with backward stepwise variable selection was used to identify the independent predictors of survival at initial visit.

Results: The ΔFS score at initial visit was a significant predictor of survival in ALS (p<0.001), and remained significant when adjusted for age and site of onset (p<0.001). 3 prognostic subgroups emerged, with a ΔFS score of <0.47 associated with a median survival of 2.4 years, which was significantly greater when compared with an initial ΔFS score of between 0.47 and 1.11 (1.6 years, p<0.05) and a score >1.11 (0.7 years, p<0.001). Importantly, multiple Cox proportional hazards modelling identified ΔFS as a highly significant independent predictor of survival in ALS (p<0.001) along with site of disease onset (p<0.01).

Conclusions: Rate of disease progression appears to be a simple and sensitive clinical prognostic biomarker in ALS that could be potentially utilised in clinical practice and future therapeutic trials.