Objective: To evaluate the psychometric properties of the Modified Fatigue Impact Scale (MFIS) in four different European countries.
Methods: Individuals with definite multiple sclerosis (MS) were selected from centres in Italy (n =50), Spain (n =30), Slovenia (n =50) and Belgium (n =51) and completed the MFIS and the Fatigue Severity Scale (FSS) twice (interval < or =3 days).
Results: In all four samples, the MFIS demonstrated a good reproducibility (intraclass correlation coefficient > or = 0.84), with no significant differences between countries (P =0.77). Moderate correlations were found between the MFIS and FSS. No significant correlations were found between the MFIS and age, gender, type of MS, duration of the disease or EDSS score. Factor analysis of all samples (n = 181) could not completely confirm the original assumptions concerning the physical, cognitive and psychosocial component The total score, the physical and the cognitive subscale of the scale were homogeneous (Cronbach's alpha 0.92, 0.88 and 0.92, respectively), but the psychosocial subscale had a Cronbach's alpha of 0.65.
Conclusions: No cultural or linguistic differences were found in the psychometric properties of the Belgian, Italian, Slovenian or Spanish version of the MFIS. We recommend this scale for research purposes and in clinical practice. Due to the limited value of the psychosocial subscale, we recommend interpreting this subscale with caution.