Validity and reliability of the Persian-version of fatigue impact scale in multiple sclerosis patients in Iran

 Introduction: Fatigue is a common presentation in Multiple Sclerosis (MS).This study was conducted for evaluation of content, convergent and divergent validity besides test-retest, inter-rater and internal consistency of reliability of Persian-version of fatigue impact dcale (P-FIS) in Iranian patients with MS for the first time in Iran. Materials and Methods: In this descriptive analysis, 140 MS patients and 140 healthy control participated and completed the following assessments: P-FIS, fatigue severity scale (FSS), SF-36 questionnaire, mini-mental state sxamination (MMSE) and the data were analysied by using SPSS (version 17). Spearman’s correlation was used for convergent validity of the P- FIS test with the FSS and the SF-36 tests, Mann -Whitney U test used for divergent validity, The Intra-class correlation coefficient used for inter-rater and test-retest reliability and and finally cronbach’s α was used to evaluate of internal consistency. Results: Content validity index of scale was 0.85. FIS had a convergent validity with the quality of life (SF-36) and also FSS. The ICC values for inter rater reliability in the physical, cognitive, and social sections and the whole questionnaire were 0.89, 0.86, 0.95 and 0.98, and for test-restest reliability were 0.86, 0.78, 0.92 and 0.93, respectively. The above findings together with the Cronbach’s α of 0.953 indicated a high reliability for the FIS Persian version. Conclusion: Having shown a sound validity and reliability, P-FIS retains the capability for being used in assessment of fatigue on the daily activities and evaluation the scale of the effects of treatment and rehabilitation interventions on fatigue amongst Persian-speaking patients suffering from MS.