Psychometric properties of an Arabic translation of the modified fatigue impact scale in patients with multiple sclerosis

Abstract

Purpose To translate and validate the modified fatigue impact scale into Arabic (MFIS-A) in patients with multiple sclerosis (MS). Methods A total of 116 patients with relapsing remitting MS and 59 healthy participants were recruited. Fifty patients filled the MFIS-A twice with one week difference. Reliability was assessed by measuring Cronbach’s α and intraclass correlation coefficient (ICC). The MFIS-A was correlated with the fatigue severity scale (FSS), the vitality domain of the Short Form 36 (SF-36V), the fatigue visual analogue scale (VAS-F), and the Beck Depression Inventory II (BDI-II) to assess validity. Dimensionality of the MFIS-A was investigated. A receiver operating characteristic (ROC) curve analysis was done and specificity and sensitivity were calculated. Results Factor analysis (based on 116 patients) revealed that the MFIS-A consists of two subscales: the physical/social and the cognitive subscales. The MFIS-A showed excellent test–retest reliability (ICC = 0.920) and internal consistency (Cronbach’s α = 0.968). The minimal detectable change with 95% confidence interval was 14.68 (32.0%). The MFIS-A showed strong positive correlation with FSS and BDI-II, moderate positive correlation with VAS-F, negative moderate correlation with SF-36V, and weak correlation with EDSS. The MFIS-A differentiated healthy participants from patients with 79.3% sensitivity and 89.8% specificity. Conclusions The MFIS-A showed good validity and reliability indicating its usefulness as an assessment measure for patients with MS. IMPLICATIONS FOR REHABILITATION MFIS-A is a valid and reliable tool for fatigue evaluation for patients with relapsing remitting MS. The optimal cutoff scores of the total MFIS-A, the physical/social, and cognitive subscales which indicate fatigue are 35.5, 18.5, and 15.5, respectively. Changes of 14.68 or more points may indicate a clinically important change (a true change) in fatigue in patients with MS.