Abstract
BackgroundFatigue is a common and debilitating symptom in multiple sclerosis (MS). Best-practice guidelines suggest that health services should repeatedly assess fatigue in persons with MS. Several fatigue scales are available but concern has been expressed about their validity. The objective of this study was to examine the reliability and validity of a new scale for MS fatigue, the Neurological Fatigue Index (NFI-MS).MethodsQualitative analysis of 40 MS patient interviews had previously contributed to a coherent definition of fatigue, and a potential 52 item set representing the salient themes. A draft questionnaire was mailed out to 1223 people with MS, and the resulting data subjected to both factor and Rasch analysis.ResultsData from 635 (51.9% response) respondents were split randomly into an 'evaluation' and 'validation' sample. Exploratory factor analysis identified four potential subscales: 'physical', 'cognitive', 'relief by diurnal sleep or rest' and 'abnormal nocturnal sleep and sleepiness'. Rasch analysis led to further item reduction and the generation of a Summary scale comprising items from the Physical and Cognitive subscales. The scales were shown to fit Rasch model expectations, across both the evaluation and validation samples.ConclusionA simple 10-item Summary scale, together with scales measuring the physical and cognitive components of fatigue, were validated for MS fatigue.
Highlights
Fatigue is a common and debilitating symptom in multiple sclerosis (MS)
A major problem has been the absence of a clear definition of fatigue [5,6,7] and, there is debate regarding the possible dimensionality of the phenomenon, with some arguing that fatigue can only be understood as a multidimensional entity,[8] while others argue that it is unidimensional [9]
The nascent scale was put to an expert, multidisciplinary panel of ten professionals experienced in MS and fatigue, comprising: MS specialist nurses, MS specialist physiotherapists and occupational therapists, consultants in neurology and neurorehabilitation each with specialist interest in MS, a consultant rheumatologist and a clinical physiologist in sleep medicine, in order to confirm that items and their wording were reasonable
Summary
Fatigue is a common and debilitating symptom in multiple sclerosis (MS). Best-practice guidelines suggest that health services should repeatedly assess fatigue in persons with MS. The Modified Fatigue Impact Scale (MFIS)[10] has been recommended by the MS Council as an outcome measure for fatigue [5] Despite their widespread use, some limitations have recently been observed with respect to these scales, suggesting that they do not satisfy modern standards of outcome measurement [11,12]. Some limitations have recently been observed with respect to these scales, suggesting that they do not satisfy modern standards of outcome measurement [11,12] Such deficiencies suggest a need for a better definition of, and a high-quality measurement instrument for, fatigue [6]. As a result of qualitative analysis, as a:
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