Development and evaluation of a clinical staging system for amyotrophic lateral sclerosis

Staging of disease severity is useful for prognosis, decision-making and resource planning. However, no commonly used, validated staging system exists for amyotrophic lateral sclerosis (ALS). Our purpose was to develop an ALS staging system (ALS Milano-Torino Staging) that captures the observed progressive loss of independence and function.

Clinical milestones in ALS progression were defined by loss of independence in four key domains on the ALS Functional Rating Scale (ALSFRS): swallowing, walking/self-care, communicating and breathing. Stages were defined as follows: stage 0, functional involvement but no loss of independence on any domain; stages 1-4, number of domains in which independence was lost; and stage 5, death. Staging criteria were applied to patients enrolled in a Quality of Care in ALS (QOC) study; endpoints included function (ALSFRS), quality of life (QOL; Short Form-36) and health service costs. Between-stage transition probabilities were assessed in the QOC study and in a second clinical study of lithium carbonate in ALS.

70/118 (59.3%) participants in the QOC study progressed to higher stages of disease at 12 months compared with their baseline stage. Functional (ALSFRS) and QOL measures were inversely related to disease stage. Health service costs were directly related to increasing disease stages from 0 to 4 (p<0.001). Probabilities for transitioning from a given stage at baseline in both studies were usually greatest for the next highest stage.

The proposed ALS Milano-Torino Staging system correlates well with assessments of function, QOL and health service costs. Further studies are warranted to validate this system.