Rasch measurement in the assessment of amytrophic lateral sclerosis patients.
Norquist JM., Fitzpatrick R., Jenkinson C.
This paper examines the sensitivity to change over time of the Amyotrophic Lateral Sclerosis Assessment Questionnaire (ALSAQ-40). Individuals' health status change was assessed by means of the Rasch-based Reliable Change Index (RCI) for ALSAQ-40 questionnaires completed on two occasions, three months apart. In addition, at follow-up respondents indicated how much change they had experienced since baseline via dimension-specific self reported transition questions. 764 individuals returned questionnaires at baseline and follow-up. For all dimensions, of respondents defined by the RCI as worse, a majority rated themselves as worse. However, on two dimensions over 60% of the respondents who rated themselves as being worse were defined as unchanged by the RCI. As with effect size smaller RCI cut-off points might be needed for subjects with ALS. This study confirms that the ALSAQ-40 is a valid and responsive disease specific health related quality of life instrument for use in studies of patients with ALS or other motor neuron diseases.