Validity and reliability of Persian version of Modified Fatigue Impact Scale (MFIS) questionnaire in Iranian patients with multiple sclerosis

Purpose: To determine the validity and reliability of the Persian version of the Modified Fatigue Impact Scale (MFIS) questionnaire for Iranian patients with multiple sclerosis (MS). Method: One hundred and twenty patients with MS and 75 age-matched healthy controls were enrolled. Participants were asked to answer the valid and reliable Persian version of the Beck depression inventory (BDI), Fatigue Severity Scale (FSS) and translated MFIS questionnaires. Twenty cases filed the questionnaire two weeks later to assess reliability. The intra-class correlation coefficient (ICC), Cronbach's alpha and multiple regression analysis were used. Results: The total MFIS score and subscale scores differed significantly between the patients with MS and the healthy controls. The ICCs and Cronbach's alpha values were also outstandingly high. There was a significant correlation between the FSS and MFIS scores in patients (r = 0.69, p<0.001). Also, a significant correlation was investigated between the scores of the BDI and the MFIS (r = 0.68, p<0.001). Multiple linear regression analysis between the MFIS as a dependent variable and Expanded Disability Status Scale (EDSS), BDI and disease duration as independent variables showed that the BDI and EDSS are dependent predictors of the MFIS. Conclusion: The results of this study indicate that the Persian version of MFIS can be regarded as a valid and reliable scale for assessing fatigue in Iranian patients with MS.