The ALSFRS-R: a revised ALS functional rating scale that incorporates assessments of respiratory function
Introduction
The Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) is a validated questionnaire-based scale that measures physical function in carrying out activities of daily living (ADL) of patients with ALS [1], [2], [3], [4]. It has been used in clinical trials [5], [6] as well as in clinical practice because of its ease of use and its correlation with both objective measures of disease status and levels of disability. The components of the scale group into four factors or domains that encompass gross motor tasks, fine motor tasks, bulbar functions and respiratory function [1]. The components of the scale, however, are not equally weighted. Where three questions each rate the motor and bulbar abilities only one question rates breathing ability.
In the course of conducting a clinical trial with brain-derived neurotrophic factor (BDNF), a series of queries were developed to evaluate the progression of respiratory dysfunction in ALS. In this report, we investigate the impact of adding three of these evaluation items to replace the breathing scale of the ALSFRS (Table 1, Table 1b). We tested the ability of the revised scale to assess respiratory function without altering the overall properties, utility, or validity of the original instrument. The addition of the respiratory symptom ratings resulted in an improved scale that is more sensitive to change and has better ability to predict survival than the original ALSFRS. This report is a retrospective validation of the revised scale.
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Patients and methods
The 387 placebo-treated patients who were followed as part of the BDNF Phase II–III treatment study sponsored by Amgen–Regeneron Partners constitute the population for this evaluation. The demographic characteristics and the pretreatment measures of ALS status of these patients are summarized in Table 2.
The patients were evaluated monthly for 9 months as part of a therapeutic treatment trial. Monthly evaluations performed during the trial included the ALSFRS, percent predicted forced vital
Factor analysis: internal structure of the ALSFRS-R
Factor analysis of the revised scale revealed that the evaluation items cluster into four factors that account for 73% of the total variance, as shown in Table 3. As in the original ALSFRS, these factors correspond to fine motor, gross motor, bulbar, and respiratory function [1]. The rotated factor loadings of the revised scale correspond well to those previously reported for the original scale as applied to other ALS patients enrolled in earlier trials. The new questions relating to
Discussion
The ALSFRS is a validated clinical rating scale that has been shown to accurately track progression of patients’ disability in ALS [1], [2], [3], [4]. Inclusion of assessments of ADL function such as the ALSFRS is an essential element of the design of ALS clinical trials [11]. One weakness of the original ALSFRS was that it did not weight respiratory dysfunction equally to limb and bulbar function. In the course of a large multicenter clinical trial, we developed a new questionnaire-based
Acknowledgements
This study was sponsored and funded by Amgen–Regeneron Partners.
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A complete listing of the BDNF Study Group (Phase III) members is given in .