Reliability and validity of two self-report measures of impairment and disability for MS

Abstract

Objective: To describe the results of a multicenter study that validated two new patient-reported measures of neurologic impairment and disability for use in MS clinical research. Background: Self-reported data can provide a cost-effective means to assess patient functioning, and can be useful for screening patients who require additional evaluation. Methods: Thirteen MS centers from the United States and Canada implemented a cross-sectional validation study of two new measures of neurologic function. The Symptom Inventory is a measure of neurologic impairment with six subscales designed to correlate with localization of brain lesion. The Performance Scales measure disability in eight domains of function: mobility, hand function, vision, fatigue, cognition, bladder/bowel, sensory, and spasticity. Measures given for comparison included a neurologic examination (Expanded Disability Status Scale, Ambulation Index, Disease Steps) as well as the patient-reported Health Status Questionnaire and the Quality of Well-being Index. Participants included 274 MS patients and 296 healthy control subjects who were matched to patients on age, gender, and education. Results: Both the Symptom Inventory and the Performance Scales showed high test–retest and internal consistency reliability. Correlational analyses supported the construct validity of both measures. Discriminant function analysis reduced the Symptom Inventory to 29 items without sacrificing reliability and increased its discriminant validity. The Performance Scales explained more variance in clinical outcomes and global quality of life than the Symptom Inventory, and there was some evidence that the two measures complemented each other in predicting Quality of Well-being Index scores. Conclusions: The Symptom Inventory and the Performance Scales are reliable and valid measures.