Fatigue is the most frequent and severe of symptoms causing morbidity and disability in multiple sclerosis (MS) patients. However, measuring fatigue is a difficult task. There is no clear definition; it is complex and multidimensional, and is a highly subjective symptom with many uncertainties regarding its pathophysiology. No biological or neuroimaging markers for fatigue are currently known 1 . The lack of standardization for fatigue measurement has resulted in development of several assessment instruments, but none of them is universally accepted. The Fatigue Severity Scale (FSS) 2 and Modified Fatigue Impact Scale (MFIS) 3 are the most widely used instruments for measuring MS fatigue, although limitations regarding their development and measurement properties have been reported. Moreover, they were not specifically developed for MS patients 4,5,6 . Studies using the Rasch measurement model have identified a need for certain items to be removed from the FSS [4] and MFIS [6] so that their measurements can be considered valid and reliable.In Brazil, FSS 7 and MFIS 8 have been widely used, despite the failings of their design and psychometric properties in Brazilian cross-cultural adaptation studies. These Brazilian versions did not fulfill the criteria for adequate sample size and design. Moreover, the psychometric properties of the Brazilian FSS adaptation were not assessed. Therefore, there are no Brazilian MS-specific instrument for assessing fatigue with reported methodological and psychometric properties
ABstrACtThe Neurological Fatigue Index for Multiple Sclerosis (NFI-MS) is a new fatigue assessment instrument. The aim of this study was to cross-culturally adapt and assess the psychometric properties of the Brazilian version of the NFI-MS (NFI-MS/BR). Method: Two hundred and forty subjects with MS were recruited for this study. The adaptation of the NFI-MS was performed by translation and back translation methodology. In psychometric analysis was performed the administration of the questionnaires Epworth Sleep Scale, Fatigue Severity Scale, Modified Fatigue Impact Scale, Multiple Sclerosis Impact Scale-29, NFI-MS/BR and Pittsburgh Sleep Quality Index with retest of the NFI-MS/BR after 7 days. Results: Reliability was assessed (intraclass correlation coefficients between 0.77 and 0.86), and validity by testing 41 hypotheses about expected correlations between subscales and confirmed 36. The majority of correlations were demonstrated. Conclusion: The NFI-MS/BR is a cross-culturally adapted, valid, and reliable instrument for assessing MS fatigue among Brazilian subjects.Keywords: multiple sclerosis; fatigue; assessment; validation studies; psychometrics.
resumo O índice neurológico de fadiga na esclerose múltipla (EM) (NFI-MS) é um novo instrumento de avaliação da fadiga. O objetivo deste estudo foi adaptar transculturalmente e avaliar as propriedades psicométricas da versão Brasileira do NFI-MS (NFI-MS/BR).Método: Duzentos e quarenta indivíduos com EM participaram deste estudo. A adaptação do NFI-MS/BR f...